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Biology Lesson Note for SS1 (Second Term) 2024

Biology lesson note for SS1 Second Term is now available for free. The State and Federal Ministry of Education has recommended unified lesson notes for all secondary schools in Nigeria, in other words, all private secondary schools in Nigeria must operate with the same lesson notes based on the scheme of work for Biology.

Biology lesson note for SS1  Second Term has been provided in detail here on

Biology Lesson Note for SS1 (Second Term) [year] 1









For prospective school owners, teachers, and assistant teachers, Biology lesson note is defined as a guideline that defines the contents and structure of Biology as a subject offered at SS level. The lesson note for Biology for SS stage maps out in clear terms, how the topics and subtopics for a particular subject, group works and practical, discussions and assessment strategies, tests, and homework ought to be structured in order to fit in perfectly, the approved academic activities for the session.

To further emphasize the importance of this document, the curriculum for Biology spells out the complete guide on all academic subjects in theory and practical. It is used to ensure that the learning purposes, aims, and objectives of the subject meant for that class are successfully achieved.

Biology Lesson note for SS1 carries the same aims and objectives but might be portrayed differently based on how it is written or based on how you structure your lesson note. Check how to write lesson notes as this would help make yours unique.

The SS1 Biology lesson note provided here is in line with the current scheme of work hence, would go a long way in not just helping the teachers in carefully breaking down the subject, topics, and subtopics but also, devising more practical ways of achieving the aim and objective of the subject.

The sudden increase in the search for SS1 Biology lesson note for Second Term is expected because every term, tutors are in need of a robust lesson note that carries all topics in the curriculum as this would go a long way in preparing students for the West African Secondary Examination.

This post is quite a lengthy one as it provides in full detail, the Biology-approved lesson note for all topics and sub-topics in Biology as a subject offered in SS1.

Please note that Biology lesson note for SS1 provided here for Second Term is approved by the Ministry of Education based on the scheme of work.

I made it free for tutors, parents, guardians, and students who want to read ahead of what is being taught in class.

SS1 Biology Lesson Note (Second Term) 2024



  • Tissues and Supporting Systems II
  • Basic Ecological Concepts
  • Basic Ecological Concepts II
  • Functional Ecosystem
  • Energy Transformation in Nature
  • The Relevance of Biology to Agriculture
  • The Relevance of Biology to Agriculture II
  • Micro Organisms Around Us
  • Micro-organisms in Action
  • Towards Better Health
  • SS1 Biology Second Term Examination (Mock)



1.Different Types of Supporting Tissues

2.Functions of Supporting Tissues in Plants


Types of Supporting Tissues

Plants have various types of supporting tissues that make them up.  Like animals, these tissues help them to stand some meters above the ground without falling. They have definite shape, strength, rigidity and to resists external force like wind and water.

Tissues that give support to plant are:





  1. Parenchyma
  • Tissues made up of living unspecialized plant cells that are roughly spherical in shape
  • They are composed of mainly cellulose and a large vacuole containing cell sap
  • It gives rigidity to plants as a result of tightly packed cells.
  • Other tissues are derived from parenchyma.
  • They possess thin wall and are found in the cortex of stems, leaf mesophylls, and flesh of fruits.
  1. Collenchyma
  • Consist of living cells that are thickened at the corners.
  • Collenchyma cells are found beneath the epidermis in stems and petioles and around the veins in dicot leaves.
  • Usually polygonal elongated cells with tapering ends.
  • It enable flexibility and resilience.
  • Does not support secondary growth in plant.
  1. Sclerenchyma
  • This is made up of cells impregnated with lignin that gives the plant hardness, rigidity and mechanical support.
  • They are made up of dead cells (fibres and sclereids/stone cells)
  • Fibres are made up of narrow polygonal elongated cells.
  • It has thick secondary walls.
  1. Xylem of Wood Tissue
  • It is the tissue that conducts water and mineral from the soil to the plant and vessels.
  • Xylem is made up of (a) fibres (b) vessels (c) tracheids and (d) parenchyma.
  • Has strengthening function that undergo secondary growth.


Plant Tissues

Stems differ between gymnosperms (conifers and related plants) and angiosperms (flowering plants) and between the two divisions of angiosperms—monocotyledons and dicotyledons. Common to all of them, though, are basic tissue types: vascular tissue (xylem and phloem), which conducts water and nutrients to the cells of the plant; ground tissue, called pith at the center of the stem, which surrounds the vascular tissue; and dermal tissue, a protective layer.


Nectarine Tree

The nectarine tree is a variety of peach tree that produces a smooth-skinned fruit called a nectarine. The color and seed of the fruit are very similar to that of the peach. Nectarine seeds have been known to grow trees that bear peaches and peach trees have been known to bear nectarines. Commercial farming of nectarines is extensive in California.

Functions of Supporting Tissues in Plants

The following are supporting tissues in plants:

1.It gives definite shape to the plant.

2.Epidermis, the outmost skin determines the structure of the plant and how it looks.

3.Strength: Collenchyma cells, sclerenchyma cells, xylem vessles and turgid parenchyma cells have been identified as tissues that strengthen the plants; walls are thickened to provide strength to plant.

4.Rigidity; Supporting tissues gives rigidity that plant needs to withstand blows from outside.

5.Resilience and Flexibility; By the help of supporting tissues, plant sway in the direction of the wind, breezes, and water without being moved.


1.List four plant tissues and discuss any one of your choice.

2.Mention three cells of the xylem tissue

3.State three functions supporting tissues in plants.



1.Meaning of Ecology

2.Ecological Concepts

3.Components of an Ecosystem

4.Local Biotic Communities or Biomes


Meaning of Ecology

Ecology is the study of living organisms in relation to their environment.

The study deals with the relationship of living organisms with one another and with the environment in which they live. Ecology measures factors affecting the environment; it studies the distribution of living organisms and how they depend on one another and their non-living environment for their survival.

Ecology is divided into two

(i) Autecology which is the study of a single individual organism or a single species of organism and their environment. E.g. the study of Tilapia fish in a particular stream.

(ii) Synecology which is the study of inter–relationships between groups of organisms or species of organisms living together in an area. E.g. the study of all organisms in a particular stream in relation to their environment.

Ecological Concepts

  1. Environment: This refers to all the factors in an organism’s surroundings, living or non-living. The factors include the place where the organism lives and the physical conditions in the place, the food, water and air it takes in, the animals that prey on it and the disease that affect it.
  2. Habitat: This is the place where an organism lives. It is the place that is suitable to the organism’s way of life e.g. the habitat of fish is water.

Examples of Habitat

Examples of habitats include:

(i) Aquatic habitats e.g. puddles, streams, ponds, seas, oceans.

(ii) Terrestrial habitats e.g. savanna, rain, forest, desert, etc.

(iii) Arboreal habitat i.e. tree tops and tree trunks.

  1. Ecological Niche: This is the functional role and the space/specific portion of habitat occupied by a particular organism or species. E.g. a caterpillar and an aphid may live on the same plant but occupy different positions. The caterpillar lives on the leaves and feeds on them while the aphid lives on the young shoot stem and sucks sap from it. The functional role includes the organism’s behaviour, its feeding habits and breeding habits i.e. the activities carried out while occupying the spaces in the habitat.
  2. Population: This is the total number of all organisms of the same species or kinds, living together in a given area/habitat. E.g. the total number of tilapia fish in a pond constitutes the population of Tilapia fish in that habitat.
  3. Community: This is made up of all the populations of living organisms that exist together in a habitat. It is any natural occurring group of different organisms living together and interacting in the same habitat. E.g. the community on a rotting log will include insects like termites, ants, lizards, small birds and decomposers such as bacteria and fungi.
  4. Biosphere: This refers to all parts of the atmosphere, hydrosphere and lithosphere where life can be found. It is the largest and highest level of biological organization and is made up of various ecosystems.
  5. Ecosystem: This is self-supporting unit that is made up of a living part and a non-living part. It is a community of plants and animals interacting with themselves and with the non-living factors in their environment.


1.Define ecology

2.Mention four ecological concepts and explain them

Components of an Ecosystem

The living part of the ecosystem is called its biotic component while the non-living parts are called the biotic component.

(a) Biotic component: This includes all living things/organisms in an environment. It is also called the biotic community. It is made up of;

(i) Food producer’s e.g. autotrophs (green plants), chemosynthetic bacteria and protophyta.

(ii) Food consumer’s i.e. heterotrophs such as animals, protozoa and some bacteria.

(iii) Decomposer’s i.e. saprophytes like fungi and some bacteria.


(b) Abiotic component: This consists of abiotic resources and abiotic conditions

Abiotic resources: These are what organisms need so as to stay alive. E.g. sunlight (a source of energy) and inorganic nutrients like water, nitrogen, carbon dioxide, phosphorus etc.

Abiotic conditions: These are those factors that determine the kind of organisms that are found in a particular ecosystem. These factors affect the behaviour, growth and breeding patterns of organisms, they include;

(i) Climatic factors such as temperature, wind, light intensity, humidity, water currents, turbidity, rainfall, e.t.c.

(ii) Edaphic factors such as soils, rocks, topography, etc.

Other factors include air, water, storms, etc.

Characteristics of an Ecosystem

The following are the characteristics of an ecosystem:

(i) There is a flow of energy

(ii) There is recycling of inorganic nutrients.

The major interaction between the biotic and abiotic components involves feeding. Food producers like plants, trap sun-light energy and nutrients (e.g. carbon dioxide, nitrogen) etc. from the abiotic environment to make food. The energy and nutrients in the food is passed on to heterotrophs (consumers) such as animals which feed on plants or on one another. The animals and plants eventually die and decomposers feed on them thereby obtaining their own energy. However in the process, the decomposers release the nutrients in the animals and plants back into the abiotic environment (i.e. the soil). These nutrients can be re-used again by the food producer’s. Plants also give out oxygen during photosynthesis and this is used by animals for respiration. Animals give off carbon dioxide during respiration which plants take up.

NB: As the energy in food is passed from one organism to another it eventually escapes into the environment and cannot be re-used.


1.Define (a) biotic factor (b) abiotic factor

2.Give two examples each of the concepts defined above

3.What characteristics make an ecosystem a self- supporting unit.



Biomes are large natural terrestrial (land) ecosystems. It is the largest community of organisms interacting with the non-living environment. Biomes are identified by their vegetation. Examples include forest, desert, savannas, etc. The type of vegetation is largely determined by climatic factors especially rainfall and temperature, as such, regions in the world which have similar climates also have similar biomes.

Local Biomes in Nigeria

This can be grouped into two major zones

1.The forest zone

2.Savanna zone

  1. The forest zone: This is made up of vegetations having mainly trees, they include:

(a) Mangrove swamp: A forest of tall woody trees with aerial roots. The rainfall is high and the soil is water logged throughout the year. Plants here include the white and red mangroves, raffia palms and coconut.

Mangrove swamps are found in states like the Delta, Cross River, Bayelsa etc. The climate is hot and wet throughout the year. Rainfall is heavy usually above 2500mm and the average monthly temperature is around 26ºc for most months of the year.

(b) Tropical Rainforest: Consists of tall trees with buttress roots, with evergreen and broad leaves. The trees exist in canopies i.e. different layers, and prevent sunlight from reaching the forest floor, thus the vegetation on the forest floor is sparse. Epiphytes and climbers are common features in the trees.

The climate is hot and wet throughout the year. The mean annual temperature is 27ºc while the mean total annual rainfall is 2000mm. These forests are found in states like Oyo, Edo, Cross River, Ogun, Ondo, Imo and Rivers State.

  1. Savanna zone: This is made up mainly of grasses and includes;

(a) Southern Guinea Savanna: Consists mainly of tall grasses, with a few tall trees with broad leaves. The trees are scattered and deciduous. Examples include the locust beans trees, shear-butter and isobelina.

It has a moderate rainfall of between 100-150cm per annum. They are located in Enugu, Kogi, Benue, Kwara, Osun, Oyo, Ebonyi, and Ekiti States.

(b) Northern Guinea Savanna (Sudan Savanna): This has short but numerous grasses. The trees are scattered, short and deciduous. The trees have thorns while others have thick barks. The trees include acacia, date palm, baobab and silk cotton plants.

The rainfall is low, about 50-100cm per annum. They may be found in states like plateau, Kaduna, Bauchi, Niger, Taraba, Adamawa and Kano.

(c) Sahel Savanna: It has very short and scanty grasses. There are short and tough shrubs or trees. The plants are mainly drought resistant and scattered examples include acacia, gum arabic and date palm.

The temperature is very high and rainfall is very low, below 50cm per annum. It may be found in States like Bornu, Katsina, Sokoto, Yobe, Kebbi, Zamfara, Kano and Jigawa.



1.What is a biome and how can it be identified?

2.Mention the two major biomes in Nigeria and the types.


Make a drawing of the map of Nigeria and outline the local biomes.


Make a local visit to any nearby vegetation and make a report of your observations.





1.Major Biomes of the World

2.Population Studies by Sampling Method

3.Ecological Factors

4.Simple Measurement of Ecological Factors

5.Relationship between Soil Types and Water Holding Effects of Soil on Vegetation

6.Practical Guides on Soil


Major Biomes of the World

Zones of different biomes occur from the equator to the arctic and to the antarctic due to differences in climate. In the equatorial and tropical areas where temperature and rainfall are high all year round, tropical forests occur while in the cold arctic regions, treeless plains called tundra are found.

Climates change with distance from the equator and also with height above sea level, as such zones of different biomes occur from the equator to the poles and on a mountain side.

Examples of Major Biomes of the World

  1. Tropical rain forests: These consist of dense forests with many types of trees, epiphytes and climbers. Rainfall is abundant throughout the year and an average temperature of 27ºc is recorded throughout the year. Located around the equator e.g. around coasts of West Africa, Amazon basin of  South Africa, etc.
  2. Temperate forests: These consist of broad-leaved deciduous trees which shed their leaves during winter. A lot of different plants grow at many levels from the ground as the trees are not densely packed as in the tropical forest. It has a moderately wet climate and a dry or cold season. Examples are found in North America, lowlands of North – West Europe (e.g. France), and Britain.
  3. Coniferous forest: These consist of needle leaved, evergreen conifers e.g. pines, fires and spruces. Only a few types of tree are found in these forests. Other plants such as shrubs, ferns and mosses are also present. The temperature is cool and rainfall is light. There is also light snow. Examples are found in Eurasia and North America.
  4. Temperate shrubland: Consist of drought-resistant shrubs, aromatic plants and dwarf trees. The temperature is very high (over 30ºc), rainfall is low, the summers are hot and dry and the winters are mild and rainy. Examples are found in North-Eastern Brazil, Australia, and close to the Sahara in West Africa.
  5. Savanna: These are tropical grasslands with few scattered trees. It has a moderately dry climate, a warm dry season and a hot rainy season. Examples are found in Central America, Interior of Brazil, West Africa, East Africa, and South-East Asia.
  6. Temperate grassland: Consist of large stretches of perennial grasses growing on very fertile soil. Examples are the steppes, prairies, plains, pampas and veld. The climate is moderately dry with a cold winter and hot summer. Examples are Found in the interior continents in Asia, North America, South America, (Argentina), South Africa and Australia.
  7. Desert: Consist of very sparse vegetation which are mainly succulent perennials with deep root systems and annuals which exist mainly as seeds, germinate and grow rapidly, flower and produce seeds during brief periods of rain. Rainfall is very low and temperature is very high. E.g. Sahara desert (North Africa), Arabian Desert (Arabia), e.t.c.
  8. Tundra: Consists of treeless marshy vegetation composed mainly of dwarf shrubs, grasses, sedges, lichen and moss. The climate is clod with long icy winters and very short summers. The average temperature is 10ºc. Examples are the coastal strip of Greenland, Northern Canada and Alaska, Arctic seaboard of Eurasia.
  9. Mountain vegetation: Consist of evergreen rain forest occurring on the slopes of mountains. The forests are less luxuriant than the tropical rain forest. The Afro-alpine vegetation occurs at height above 3000m on mountains. The vegetation consist mainly of heaths, grasses and sedges. In Africa it is found in Cameroon mountain, Kenya highland and Kilimanjaro mountain. Temperature decrease with altitude. Rainfall is heavy on the windward side and less on the leeward side of the mountains.



1.List six biomes of the world

2.Briefly discuss two biomes of the world.


Population Studies

A population is defined as the total number of organisms of the same species living together in a given area at a particular time. In any ecosystem, the community is made up of many populations of different species.

To study a habitat’s populations, the following are usually investigated.

1.The type of organisms in the habitat: This involves listing all the different types of populations found in that particular habitat. This helps to determine the relationships that exist between the different organisms in the habitat.

2.The dominant species: This refers to the species of organisms in a community which exert a great influence on the habitat and on the other populations. Dominance may be expressed in terms of their number, size, the portion of space occupied and contribution to the energy flow of the habitat.

3.The characteristics of the population: This refers to;

(a) Population size: The total number of individuals of the same species in the habitat  (the total numbers of individuals in a population). A large population stands a better chance of surviving unfavourable conditions such as fires, diseases, harsh climate changes, while a small population can be easily wiped out. A large population also has the advantage of increasing its vigour through breeding which invariably increases its ability to withstand adverse conditions.

(b) Population density: This is defined as the number of individual organisms per unit area or volume of the habitat.

Mathematically represented as;

Population density=Total population or Population sizeArea of habitat

Example: If an area of land of 100m² has an elephant grass population of 1000 plants, the density of elephant grasses will be;

Total number of individualsTotal area=1000100m2 elephant grasses=10∅∅1∅∅m2 elephant grasses=10 elephant grasses/m2

Population density can be used to estimate the total number of individuals of a population i.e. population size.

(c) Population frequency: This refers to how often the species occurs at different sites in its habitat. It is recorded as the number of times the organism is sited (seen).

(d) Population growth rate: This refers to the total and final effect of birthrate and death rate of organisms in the habitat.

(e) Percentage cover: This is the area of ground or space covered (or occupied) by a given species its habitat. It is expressed in percentage.

(f) Distribution: This refers to the way in which individuals of a particular population are arranged in a given habitat. The individuals may live in clumps, they may be evenly spaced or randomly spaced.

Example: If the western half of the habitat contained ¾ of the elephant grasses, then,

Density =34×1000=75Ø5Ø=15 grasses/m^2

Methods of Studying Populations

To conduct population studies the following procedure is used;

1.Choose the habitat to be studied

2.Choose a sampling method

3.Identify the species in the habitat

4.Collect, count and record the different types of organisms present.

5.Repeat the population studies at different periods.

The following methods can be used to study specific populations:

  1. Collection of plants: In a small area plants are easy to count and their distribution can be recorded on a map or scale diagram of the area, however for larger areas quadrats or transects are used.

(a) Quadrat Sampling: A quadrat is made of a square or rectangular piece of wire, plastic, wood or metal frame with predetermined area. E.g. the area of a quadrat  may be 25cm². A quadrat is used to sample the number of plant species in a habitat. It is not suitable for sampling animals because they move around so much. A quadrat is used by throwing it over the shoulder at random several times and on each landing, the area covered/enclosed by it is observed. The type of plant species and their number within the quadrat are recorded. From the results, the average number of plant per m² is calculated. If the area of the habitat is known, the total number of plants it contains can be estimated.

Permanent quadrats, with mapping grids attached can be made to study seasonal variations of plants. These quadrats are sturdier, larger and remain permanently fixed on a marked area.

(b) Transect method: A marked tape is used in this method. The tape is marked at convenient intervals and then stretched across the area to be studied. The plants encountered at the interval marks are counted and recorded. This procedure is repeated a few times. In this way, a fairly accurate estimate of the number and types of plants in the habitat are obtained. Plants are usually collected in plastic bags and then pressed and dried in a plant press. The dried plants are mounted on stiff paper, fixed in position with masking tape/cellotape and labeled with both the scientific and common names.

  1. Collection of Animals: Animals are more difficult to collect than plants; however their presence can be inferred by looking for signs of their presence such as nests, eggs, feaces, tracks, feathers, etc and by studying the vegetation with which they are associated. To study animals different types of nets and traps are used in capturing them. The following methods can be used.

(a) Capture – Recapture method: In this method animals of one type in a particular area are caught, counted and marked with ink and released. Their number is recorded as A1. The following day another set is captured and the number recorded as A2.This second batch may include animals which had been caught and marked the previous day, their number is recorded as A3. The population of animals present in the area is found using the formula;

Population in area A1×A2A3

This method is based on the assumptions that;

1.Individuals do not move out of or into the ecosystem

2.The marked individuals are randomly distributed in the population.

3.The marked individuals are a random sample.

4.The initial capture and markings do not influence recapture.

5.That none of the marks have worn off during the interval between the two catches.

NB: The results obtained by this method are approximations.

(b) Collection of soil animals with quadrats: The soil animals in an area can be studied by collecting samples of soil from several sites chosen by tossing a quadrat randomly. A 25% sodium chloride solution is added to each soil sample and the animals are collected as they float in the solution.

For earthworms, the sites chosen with the quadrat are irrigated with 25% formalin solution and the earthworms are collected as they move to the surface of the soil.


  1. What are the major investigations carried out when studying a habitat?
  2. A pond with an area of 200m² has a duckweed population of 1,500 plants. Find

(a) The population density

(b) If the western half of the habitat contained ¾ of the duckweed. What is the density of the eastern half?

  1. Explain what a Tullgren’s funnel is and what it is used for.
  2. Make a list of traps used for capturing animals for study and describe how captured animals are kept or preserved.

Factors That Affect Populations

Populations in a habitat may show changes in size or distribution. These changes may be due to;

1.Natality (birth rate): Increase in birth rates especially during breeding periods, lead to increase in population size while a decrease in birth rate results in a decrease in the population.

2.Mortality (death rate): This refers to the rate at which organisms die. An increase in death rate leads to a decrease in the population and vice versa.

3.Immigration: This is the movement of organisms from different habitats into a particular habitat. This increases the population size of the habitat being moved into.

4.Emigration: It is the movement of organisms out of a habitat ant it leads to a decrease in the population. Emigration may be caused by scarcity of food, unfavourable conditions, seasonal climate changes or breeding purposes.

5.Availability of food: An abundance of food in a habitat tends to lead to an increase in the population of organisms due to increase in birth rate (reproduction) and influx of organism from other areas  and vice versa.

6.Seasonal climate changes: Adverse climate changes may lead to a decrease in number of organisms due to death or emigration. Favourable conditions leads to an increase in population.

7.Natural disasters e.g. fire; flood, drought etc. may lead to a decrease in population due to death and emigration.

(others include availability of water, availability of space, war)


Ecological Factors

These are factors in the environment that influence life in the ecosystem. These factors affect the living organisms or cause changes in the habitat (aquatic or terrestrial).

These factors are grouped into two

1.Biotic factors

2.Abiotic factors

  1. Biotic factors

The biotic factors are those concerned with the effects of plants and animals on one another in a given habitat e.g. competition, predation parasitism, etc.

  1. Abiotic factors

Abiotic factors include climate topographic (or physiographic) and edaptic (soil factors). Variations in the ecological factors bring about changes in the habitat. Abiotic factors also determine the type of biotic community found in a habitat.

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Ecological Factors Affecting Terrestrial Habitats

  1. Topographic Factors: These factors are associated with the structure of the habitats e.g. effects of hilts, valleys, plains mountains and rivers. These factors bring about variation in the vegetation and types of animals in an area.

Topographic factors include:

(a) Altitude (elevation): This refers to height of the land above sea level. This affects the growth of plants and the level of erosion in an area. As altitude increases, temperature falls by approximately 1ºc per 150metres, as a result of this, mountain tops are generally cold places cold air causes clouds to condense and fall as rain, thus the annual rainfall on mountains is high especially on the windward side. As one ascends a mountain, the air become less dense, there is less of it to filter the sun’s rays, so organisms at the top of mountains are exposed to intense solar radiation.

(b) Slope: Water flows faster on a steep slope than on a gentle slope as such, run-off  is greater and less water sinks into the soil on steep slopes. Also, erosion tends to be more. Gentle slopes are more favourable to plant growth.

(c) Exposure: This refers to the extent to which living things are not protected from climatic factors such as rainfall, sunshine and wind. Exposure is usually high on mountains and low within a forest. Winds tend to be stronger in exposed habitats and relative humidity is lower than in sheltered habitats. Low degree of exposure ensures the availability of nutrients to plants.

  1. Edaphic Factors: These are factors related to the nature of soil particles. The word edaptic refers to the influence of soils on plants and animals. Differences in the soil of a locality usually produce difference in vegetation since plants are dependent on the soil and the type of plants determine the type of animals that will be found in the habitat. Edaphic factors include:

(a) Soil Types: this could be sand, loam or clay. The type of soil determines the fertility of the soil, its porosity and water retaining capacity.

(b) Soil Texture: The amount of sand, silt and clay in a soil affects its water retaining capacity. Soil texture refers to the degree of fineness or coarseness of soil particles. It also affects leaching and erosion.

(c) Soil structure: This refers to the arrangement of the various soil particles in soil. This affects the level of soil aeration and percolation and the type and level of soil organisms in the soil.

(d) Soil pH: The pH of soil also affects the type of plants in the habitat e.g. some plants grow best in acid soils while others prefer alkaline conditions.

  1. Atmospheric factors (Relative Humility): This is a measure of the amount of moisture in the air. It affects the rate of transpiration from plants and evaporation from animals. As relative humidity falls, evaporation and transpiration rise as such organisms that live in areas where humidity is low must prevent water loss from their body surfaces. E.g. in deserts, the leaves of plants like the cactus are reduced to spines to prevent loss of water.


Ecological Factors That Affect Aquatic Habitats

  1. Salinity: This refers to the concentration of salts in the water. Salinity affects the movement of water and salts across the body tissues of aquatic organisms. Salinity is low in fresh water, high in sea water and moderate in brackish water. Aquatic organisms have to maintain the osmotic balance between their body fluids and their aquatic surroundings in order to survive. Those living in fresh water have adaptive features which enable them get rid of excess water that enters their bodies; those living in sea water have body fluids with almost the same salt concentration as the sea water while those living in brackish water have body tissues that can tolerate wide and sudden fluctuations in salt concentration of their body fluids.
  2. Depth Of Water: As a body of water becomes deeper, the amount of light and dissolved oxygen become less, so at the bottom of deep lakes and oceans, there may be too little light for photosynthesis as such no green plants can grow there. Shallow bodies of water such as ponds are usually well supplied with oxygen and light and support a lot of plants and animals. However, these habitats are subject to evaporation and drying up in the dry seasons, the plants and animals therefore have to develop adaptation to survive such conditions. E.g. formation of cysts by some protozoans.
  3. Turbidity: This refers to cloudiness of water. It is caused as a result of suspended materials in water. Light penetration is low in cloudy or muddy water and this hinders green plants from growing at some depths.
  4. Dissolved Gases: This refers to dissolved oxygen. Oxygen concentration of water decreases with depth. Oxygen is required by most aquatic organisms for respiration as such organisms which live in stagnant or very deep water have to be able to tolerate low levels of oxygen concentration. Organisms that require high oxygen concentration, usually live near the surface of deep water or in fast-flowing rivers and streams e.g. the simulium larva lives in fast flowing streams.
  5. Tides and Wave Action: Tidal movement refers to the regular rise and fall in the level of the sea. Organisms which live in the intertidal zone of a seashore have to be able to tolerate being alternately covered by sea-water and then exposed to air twice daily.

Wave action is also important both in the intertidal and splash zones of the seashore. Most organisms in these areas are attached to the substratum or live in burrows. Some attach themselves firmly to rocks and other immovable objects, while some others have hard body covering to prevent evaporation of water from their bodies. Waves cause the aeration of the surface waters of the open sea, thus enabling aquatic organisms to have sufficient supply of dissolved gases for their needs.

  1. Speed of Flow (currents): Plants and animals are affected by the rate at which the water flow. Some organism’s e.g. spirogyra prefer to live in slow moving stagnant water while others e.g. Tilapia, prefer fast-flowing water. Many organisms which live in fast-flowing rivers and streams have adaptations which serve to prevent them from being swept away from their support by currents in water. Water currents increase aeration and the turbidity of the water. Currents also carry warm water to colder regions and this affects the distribution of organisms.
  2. Density: Density of water varies with the type of habitat. The density of fresh water is about 1.00 while that of sea water is 1.028 at atmospheric pressure and 0ºc. It is easier to move through air than water because water is more dense, as such aquatic organisms have a streamlined shape to help them move easily through water. Some organisms that float on the surface are sensitive to changes in density e.g. eggs of aquatic organisms sink to different depths depending on the density of the water.


Ecological Factors Common To All Habitats

The ecological factors that affect both the terrestrial and aquatic habitats are mainly climatic e.g. temperature, rainfall, relative humidity, wind, high intensity hydrogen ion concentration (pH) and pressure. Of these factors temperature and rainfall determine the type of vegetation in a region.

  1. Temperature: This refers to degree of hotness or coldness. Variation in temperature results in hot or cold climate. It affects the terrestrial habitat more than the aquatic habitat. In the terrestrial habitat temperature varies with season, while in the aquatic habitat it decreases with depth.

A rise in temperature usually results in a higher rate of transpiration in plants and higher rate of metabolism in most animals (except homoiotherms). Most living organisms are killed by high temperatures and it reduces the performance of some. Low temperatures lead to inactivity or dormancy. In some organisms (e.g. tadpoles, insect larvae and bacteria) a rise in temperature results in faster rate of growth and shorter length of life-cycle. A higher rate of evaporation of water from the soil, ponds and lakes and a lower relative humidity are also observed.

Too high or too low temperature inhibits the growth and life activities of living things. However most organisms have various adaptive features that allow them to live at low or high temperatures e.g. Bears living in the arctic regions have very thick furs.

  1. Rainfall: Rain is the main source of water to most organisms. It also supplies water to soil on which land plants depends. It is also the major source of water in rivers, ponds, lakes, oceans etc. The amount of rainfall in an area has a major effect on the type of vegetation found there. Low amount of rainfall usually causes drought on land and drying up of freshwater habitats (which leads to death of animals). Too much rain causes floods and destruction of vegetation through erosion.

Rainfall increases relative humidity and also increases turbidity of streams, rivers and lakes. Rainfall is necessary for seed germination. It helps to dissolve nutrients in the soil thus making them available to plants. It is also necessary for the vegetative growth of most crops e.g. flowering and proper development of groundnut pods.

Rain water may form puddles and small pools which provide temporary habitats for mosquito larvae, algae and tadpoles. It is also necessary for the start of new termite colonies.

  1. Light: Light is necessary for photosynthesis in green plants. It affects the productivity of crops and facilitates flowering and fruiting in some plants. Light is the ultimate source of energy for all organisms. Light affects the activities of animals e.g. some animals are active during the day (butterfly) while others are active at night (cockroaches). The ultra-violet rays of the sun enable animals to manufacture vitamin D.
  2. Wind: Winds are important because they cause water currents and waves thus mixing water and making food available in aquatic habitat, Winds carry rain bearing clouds. They also determine a season e.g. In Nigeria, the S/W wind is responsible for the rainy season while the N/E wind brings the harmattan. Wind has drying effects (on land) and so it increases the rate of transpiration in plants. In an area exposed to strong winds only xerophytes can grow there. Winds also aid pollination of flowers and dispersal of seeds and fruits. Winds increase the rate of evaporation from the soil and in savanna and desert areas it is a major cause of soil erosion. Winds also play an important role in the establishment of insects in a given area.
  3. Pressure: Atmospheric pressure decreases from the depths of the ocean upwards to the higher attitude of the atmosphere. Plants and animals have special adaptations to a particular level of pressure to enable them survive. For instance in the oceans, the pressure increases by 1.03kg/m² every 10m, so organisms found at depths of about 400m live in conditions of enormous pressure but are well adapted to such conditions and will not survive at levels with lower pressure.
  4. Hydrogen ion Concentration (pH): This refers to the acidity or alkalinity of the soil or water in a habitat. pH affects the types of plants and animals in a habitat. E.g. some plants grow best in acidic conditions while others can only grow in alkaline conditions. In aquatic habitats pH varies with the salinity of the water. Freshwater is neutral while sea water is fairly alkaline (pH 8.5). Organisms like the freshwater mollusks (Mytilus) are usually absent in water with a pH less than 6 (i.e. acidic water).


Biotic Factors Affecting the Ecosystem

Biotic factors refer to the effects of plants and animals on themselves or one another. The biotic factors include:

  1. Parasitism: One organism called the parasite lives in or on another organism called the host. The parasite benefits while the host suffers harm or may die.
  2. Competition: This may occur between organisms of the same species or different species. Competition may be for food, space, mates, etc. One of the organisms will eventually over come the other.
  3. Commensalism: This involves two organisms living together. One of the organisms (the commensal) benefits from the association while the other organism neither benefits nor is harmed.
  4. Predation: This involves an organism (called the predator), killing / feeding on another organism (the prey).
  5. Trampling: Grazing animals trample on plants and invertebrates.
  6. Pollination of flowers by insects (this aids continuity and increase).
  7. Aeration of the soil by some animals e.g. earthworms, termites, etc.
  8. Support provided to climbing plants by trees or bigger plants.
  9. Shade provided by trees, etc.



1.State five ecological factors that (a) affect terrestrial habitats (b) affect aquatic habitats (c) are common to both habitats

2.Discuss two of each set of factors mentioned above.


Simple Measurement of Ecological Factors

  1. Temperature: This is measured using a mercury thermometer read in degree celcius (ºc). At least two readings are taken in a particular area of the habitat being studied to ensure accuracy. A soil thermometer is used for soil temperature, a maximum-minimum thermometer for recording the highest and lowest temperature of the day, and a waxed bulb thermometer for temperature of water at different depths in a pond, stream, etc. The waxed bulb thermometer is usually tied to a string knotted at regular intervals to indicate depth.


  1. Rainfall: This is measured with a rain gauge. This can be made from a tin can, a plastic funnel and a 50ml measuring cylinder. The amount of rainfall is calculated in millimeters, with the formula

dD2×h= rainfall for a period where;

d = diameter of mouth of funnel

h = height of rainwater in the cylinder

D = diameter of collecting cylinder

Usually, the height of the water in the cylinder indicates the amount of rainfall after every storm.

  1. Relative Humidity: This is measured using a wet and dry bulb hygrometer, or a pocket hygrometer. The pocket hygrometer is exposed to air and the reading taken after the lever arm has stabilized. The wet and dry bulb hygrometer is swung in air for 30seconds and the reading on the thermometers taken and converted to relative humidity units using a table of conversion. The hygrometer may also be kept in a Stevenson’s screen.
  2. Wind: Wind has both speed and direction. Wind direction is measured / indicated by a wind vane while wind speed is measured with an anemometer (recorded in ms־¹).
  3. Light Intensity: Is measured by a light meter or photometer. The readings on the meter are expressed in lux units. The greater the intensity of light, the higher the readings on the meter and vice-versa.
  4. Pressure: Atmospheric pressure is measured with a barometer. It is measured in millibars (or millimeters of mercury, mmHg). The readings are taken directly from a scale.


  1. Water Depth: Is measured with a meter rule or a marked and weighted line knotted at one meter intervals. The meter rule is attached to a weighted line to ensure that it is vertical in water.
  2. Water Flow: To measure the speed of flow of a water body, the distance (m) covered per unit times by a float is taken. The float may be a weight tube and the distance covered has to be pre-determined. Speed of the current is calculated in meters per second. A simple water-speed meter can be used to compare the speed of water flow at different positions in a stream
  3. Turbidity: Is measured by slowly sinking a weighted white disc called a secchi disc into the water, noting the depth at which it just cannot be seen anymore. This is not a real measurement of turbidity but a useful method of comparing the turbidity of different aquatic habitats, different sites of the same habitats, or at different times.
  4. Slope: Is measured with a simple slope gauge constructed with a meter rule to which a protractor is attached. The angle readings on the protractor are read and recorded. Small angles indicate a steep slope.
  5. Height: The height of objects like tall trees is measured using the principle of similar triangles.



State five ecological factors and describe how they are measured.

Relationship between Soil Types and Water Holding Effects of Soil on Vegetation

Soil is the uppermost layer of the earth’s crust which provides support and nutrient for plants growth and habitat for some animals. The soil is a complete mixture of mineral matter, humus, air and living organisms. Soil is classified on the basis of the size of the particles present in it. Soil particles vary in size and chemical composition, depending on the types of rock from which they were formed and how they were weathered. Those soils with a high proportion of sand are known as sandy soils; those with a high proportion of clay and silt are called clayey soils and those with nearly equal amount of sand, clay and silt are known as loamy soils. The proportions of these particles in the soil have an important effect on their properties and on the types of plants found on them.

Types of Soil

  1. Sandy Soil: This contains 80% sand and gravel and 20% of the other types of particles taken together. Large coarse particles of sand and gravel predominate.
  2. Clay Soil: This contains more fine clay (60%) and silt particles.
  3. Loamy Soil: This contains a mixture of both clay and sand with some humus in roughly equal proportion. Loamy soils are the most fertile and the humus in it gives it a mellow tilth i.e. the size of the soil particles and the air spaces between the particles are the most suitable for cultivation.

Effects of Soil On Vegetation

Soil factors play an important role in determining the vegetation of a region. Soils account for the variation in type of plants that are found in regions with similar climates. To support a rich growth of plants, soil must have the following characteristic;

(i) A rich humus content

(ii) A rich mineral content

(iii) A good water-holding capacity; this is determined by the amount of humus and clay in it.

(iv) Good soil porosity; determined by the humus, sand content and soil texture.

Sandy soil is low in plant nutrient and so it supports scanty vegetation or grassland. Clay soil has a little more amount of plants nutrients than sandy soils and thus can support light vegetation such as shrubs. Loamy soil is very fertile and can support luxuriant vegetations such as a forest.

Water Holding Capacity of Soil

Water holding capacity of soil refers to the ability of the soil to retain water. The amount of water retained by any soil depends or the size of the particles, the humus content, aeration, temperature and presence of microbes. Clay and humus retain a higher amount of the water than sand. In clay soil, most of the water is held firmly to the surface of the soil particles (hygroscopic water) and this is not usually available to plants. In sandy soil very little amount of water is retained as most of it drains off. Loamy soil is able to retain more water within its particles. This is called capillary water and is available for plants use.


Practical Guide on Soil

  1. Experiment to Determine The Water Retaining Capacity of Soil Types

Title of experiment: To compare the porosity and water holding capacity of three soil types

Materials required: Three measuring cylinders of 100cm³, cotton wool, three funnels, water, dry sand, dry clay, dry loam, stop clock, balance.

Method: Stand the three funnels in the three measuring cylinders and block the funnels with cotton wool.

1.Place an equal weight of dry sand, dry clay and dry loam in the three funnels respectively.

2.Pour 50ml of water onto each sample at the same time and allow to drain.

3.Allow the set up to stand for an hour or until the water has stopped dripping through each funnel.

4.Read the level of water in the measuring cylinder.


(a) Rate of drainage/porosity is calculated from the amount of water collected in the measuring cylinder. The more the water, the more porous the soil sample. Usually porosity is highest in sandy soil because it has large pore spaces and large particle sizes, followed by loamy soil and then clay soil which has the least drainage because of its tiny pore spaces and fine particles .

(b) Water holding/retaining capacity is calculated as follows;

Volume of water added to soil =50ml

Volume of water collected in cylinder =xml

Volume of water retained in the soil =(50−x)ml

The percentage of water retained in each of the soil samples will be


Observation: It is observed that water drained out from the sandy soil faster than the loamy soil and finally the clay soil. It was also observed that clayey soil retained more water than loamy soil and least retained by the sandy soil.

Conclusion: Sandy soil is more porous than loam which is more porous than clay. Clayey soil retained more water than the loamy soil and the sandy soil retained the least amount of water.

  1. Experiment To Compare The Capillary Action Of Soil Types

1.Take three wide glass tubes and plug each at one end with cotton wool.

2.Nearly fill the tubes with the three soil samples separately.

3.Clamp the tubes upright in a trough of water,

4.Allow the set-up to remain for 3-6 hours

5.Observe every 30mins.

Observation: It will be observed that at the early stage of the rise of water in the three tubes, it was faster in sandy soil than the clay and loamy soil samples, however by the end of the experiment the water had risen to the highest levels in loam, followed by clay but remained at a low level in the sandy soil.

Conclusion: Loamy and clayey soils have greater capillary actions due to their tiny pore spaces. The presence of organic matter in loam also enhanced its capillary. The sandy soil had poor capillary action because of its large pore spaces and large particles.



1.List the three major soil types.

2.Discuss the constituents of the soil types mentioned.

3.Compare the water holding capacities of the three soil types.

4.Describe how the height of a forest tree can be measured?

5.In a table outline the properties/characteristics of the three major soil types (at least ten properties)

6.Make large well labeled drawings of a maximum and minimum thermometer; a rain gauge, a wind vane, an anemometer, a light meter, a secchi disc, a barometer and a slope gauge.












3.Aquatic and Terrestrial


Meaning of Ecosystem

In this topic, the question a wise student will ask is; what is ecosystem? First of all, the word ‘eco’ simply means ecology so, it is ecological system. Let us consider this illustration, in a freshwater habitat where you have aquatic plant such as spirogyra, animals such as tilapia, frogs and toads. All this living things interact with the non- living environment which includes the water where they are, the atmosphere, and the soil beneath it. These living things in the environment together with the non-living environment constitute an ecological system or ecosystem. Therefore, an ecosystem is defined as the interrelationship between the living things and their non-living environment

Components of an Ecosystem

In an ecosystem, there are two major parts; the biotic or living and abiotic or non-living part. Then from the functional point of view, we have three kinds as producers, consumers, and decomposers. The producers are always green plants; the consumers are the animals, while the decomposers are the saprophytes.




Under the consumers we have the following:

1.Primary consumers, e.g. grasshopper, rat etc.

2.Secondary consumers, e.g. cat, lizard etc.

3.Tertiary consumer, e.g. hawks, snakes.

4.Omnivores, e.g. man, domestic fowl.

Decomposers are organisms which feed on the carcasses of dead producers and consumers and in the process bring about the decay of such carcasses. Large decomposers such as insects and earthworms are called macro decomposers, whereas small decomposers, such as certain bacteria and fungi are known as micro decomposers.

Some Products of Decomposition

In the process of decomposition, dead organic matter is broken down physically and chemically, and this is done in stages. Now, the product of this decomposition is inorganic compounds like carbon (iv) oxide, ammonium, ammonium compound as well as salts of elements present in the organic matter. Some gaseous products such as carbon (iv) oxide, ammonia and hydrogen sulphide can be identified as organic matter decomposes. Intermediate products of decomposition include sugars, and complex organic compound derived from protein.

Role of Decomposers

The role of decomposers is the recycling conversion of materials of dead organic materials into inorganic materials which are available to the producers in the ecosystem.

Coral Reef in the Red Sea

Coral reefs represent the most complex aquatic ecosystem found on Earth. Although coral reefs can be found between 30 degrees north and south latitude, the greatest concentration is found between 4 degrees north and south latitude in the western portions of all major oceans. There are two broad categories of coral reefs: shelf reefs and oceanic reefs. Shelf reefs include fringing reefs, platform reefs, bank reefs, and barrier reefs and are located on the continental shelf, while oceanic reefs are found off the continental shelf growing around the margins of volcanic islands. Coral reefs support greater numbers of fish and invertebrate species than any other ecosystem in the ocean.



1.Define the term ecosystem.

2.List the two major parts of the ecological system

3.Outline four classes of consumer with on example each.

4.Write the two types of decomposers.


1.Write short notes on (a) autotrophs (b) Heterotrophs.

2.Sketch the organogram of the ecosystem

3.Find out the group of consumers the Carnivores belong.

4.Give an instance in writing to show how living things interact with their non living environment.



Carry out an activity to show that heat is released during decomposition.


Food Chain, Food Webs and Trophic Levels

As living and non-living things interact, energy is transferred from one level to the other. The ecosystem actually operates as a movement where all organisms depend on the primary producers, the green plants.

  1. Food Chain

Food chain is the transfer of food energy from producers (green plants) to a series of organisms in a habitat. In the arrangement of the food chain, the natural rule is that it must start from a producer or an autotroph. Some examples of food chain are below:

1.Grass     →    Grasshopper       →       Lizard      →      Snake

2.Plankton      →      Tilapia      →     Water snake

3.Dead wood       →      Termite     →      Frog     →      Hawke

Note: that each level of competition in the food chain is called a trophic level. Looking at example 1, it represents the terrestrial habitat.

  1. Food Web

Considering food chain energy pathway, you will observe that it is a single energy pathway. In the actual sense, such simple food chains as shown above rarely exist within a community because consumers rarely depend on only one type of food. Often a particular food item is eaten by more than one consumer. Therefore, a network of interrelated food chains forms what is called a food web.

  1. Trophic Levels

These are stages at which the energy is found as it moves through the various organisms or levels of transfer in the ecosystem. Hence, trophic level refers to the part of a food chain.

  1. Food Pyramid
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Food pyramid is a representation of food chain in the food producers from the base and carnivores from the apex.

  1. Pyramid of Numbers

This is the progressive drop in the population at each higher or successive trophic level of the food chain or the relative decrease in number or organisms in a food chain as one ascends the higher trophic levels.

  1. Pyramid of Biomass

The pyramid of Biomass (or standing crop) indicates, by weight, the total mass of individuals or organisms at each trophic levels.


A Pyramid of Biomass

  1. Pyramid of Energy

This is the progressive drop or decrease in the total available energy at each higher trophic level or the progressive diminution of energy in the feeding chain as one ascends the higher trophic levels.

Differences between Pyramid of Numbers and Pyramid of Energy

Pyramid of Numbers Pyramid of Energy

  1. Size of organism is not recognized,

only numbers are counted This is based on a common

unit of energy joule

  1. Shape is not constant, it might be inverted

e.g. grasshoppers feeding on a large tree. Shape is constant

Non-cyclic Nature of Chemical Energy Transfer

The energy flow in an ecosystem is not cyclic because being an energy pyramid, it moves from the producers at the bottom of the pyramid up to a point where it cannot be used by living things anymore. It is either used by the organisms in the ecosystem or it is lost to the atmosphere. For example, energy stored in cow = energy stored in grass – (energy for cow’s activities + energy lost to the atmosphere).

Nutrient Movement

Nutrient movement refers to the chemical energy in form of carbohydrates, fats, protein, and other nutrients are distributed among producers, consumers and decomposers. It just about how nutrients flow from one energy level to the other in the ecosystem.

Energy Flow

Under this topic, we shall consider the following: food pyramid, pyramid of numbers, pyramid of biomass, and pyramid of energy. In any natural community, the number of individuals at the lower part of the food chain or web is greater than those above. Producers are therefore greater than primary consumers, and secondary consumers less in number than the primary consumers. This number reduces till the terminal group of organism is reached which have no predators depending on them for food. When these numbers are diagrammatically represented, a pyramid of numbers is obtained.


1.Explain the following with a typical example: Food Chain, Food Web, and trophic level.

2.Why is the energy flow in the ecosystem not cyclic.

3.What is nutrient movement?

4.Write a short note on energy flow.

5.State two the differences between pyramid of numbers and the pyramid of energy.

6.Define the term (i) consumers (ii) producers.

7.Sketch a diagram of typical food web

8.Classify the following organisms: cow, bacteria, green plants, herbivores, fungi, and man into producer, primary, secondary and tertiary consumer.



1.Energy Loss in the Ecosystem (i) Solar Radiation (ii) Energy Loss in the Biosphere (iii) Measure of Primary Production

2.Laws of Thermodynamics


Energy Loss in the Ecosystem

You remember that energy exists in various forms, and various forms are interconvertible and as such one form of energy can be transformed into one another form. In nature, energy transformations are brought about by living organisms. Their activities cause energy to flow through ecosystems unidirectionally. Now, how does energy get lost in the ecosystem?

Solar Energy

Only about 2% of solar energy is used by green plants while the rest is lost to the earth’s surface. Thus, energy is a limited factor in the production of autotrophs.

Energy Transformation in Nature

When primary consumer, the herbivores feed on the producers, the green plants, the secondary consumers, the carnivores in turn feed on the herbivores; the energy transferring efficiency in each stage is about 5-20% while the rest is lost to the atmosphere.

Energy Laws

Energy transformations in nature are governed by the laws of thermodynamics.

The First Law of Thermodynamics

This states that when one form of energy is converted into another, the total quantity of energy is constant (there is no net loss or gain in energy) that is to say that energy is neither created nor destroyed. Hence, in the process of burning, chemical energy of wood changes into heat and light. In a motor vehicle, energy in the form of fuel changes into mechanical energy. So, energy can only be converted from one form to the other.

Second Law Of Thermodynamics

The law states that when one form of energy is converted into another, a proportion of it is converted into heat. The second law of thermodynamics is sometimes known as the entropy law; entropy being a measure of disorder in terms of unavailable energy in a closed thermodynamic system.

How the Laws are Used to Explain Energy Flow Across the Trophic Levels

Pyramid of Energy

1.According to the first law, energy is transferred into a variety of other forms in the successive trophic level but the sum total is constant.

2.Using the second law, we observe that during energy transformation in the successive trophic levels, a proportion of it is converted into heat which is lost, hence the progressive drop in energy in successive trophic levels and also the pyramidal shape of feeding relationship.

Food Chain

1.In accordance with first law, chemical energy stored in plants, can be converted into light energy in glow-worm which in turn is converted into electrical energy in fire-fly and when eaten by man, it is converted into mechanical energy in muscular contraction without any loss or gain.

2.The second law shows that when energy flows through a food chain, only a small proportion of the energy taken up by each link is transferred to the next step. This is because at each transfer, most of the energy is lost as heat.

According to the second law:

1.In the flow of energy from herbivore to carnivore, there is loss of usable energy. This loss of energy means that les life can be maintained at highest trophic level.

2.The energy travels from one organism to another with a loss of energy each time it enters another organism. The various organisms represent trophic levels or stages of energy flow.


1.State the laws of thermodynamics

2.Explain the term entropy law.

3.How does law of thermodynamics apply to pyramid of energy?

4.Explain what happens when heat is lost in a food chain.

5.Explain various ways through which energy flow from the producer to you.




  1. Food Production and Storage

(a) Ways of Improving Crop Yield

(b) Causes of Wastage

(c) Methods of Preserving and Storing Food

  1. Population Growth and Food Supply
  2. Relationship between Availability of Food and Human Population (Effects of Storage)
  3. Government Efforts to Increase Food Production (e.g.) Agricultural Revolution


Food Production and Storage

The primary aim of agriculture is to provide adequate food for an ever increasing human population. The issue of food production, preservation, storage and wastage has been challenging to both the agriculturist and the government.

Adequate food production makes food available for teaming population to be well fed. It also earns the country foreign exchange through exportation of food crops. One the other hand, food shortage will increase death rate and cause migration of people to where food is available. There will be competition among organism which in turn leads to starvation and cannibalism. Natality or birth rate will be affected through avoidance of marriage.

(a) Ways of Improving Crop Yield

Crop yield can be improved through the following ways:

1.Breeding high yielding crops that are resistant to plant and animal disease.

2.Using fertilizers and organic manure to maintain soil structure and fertility and ensure high crop yield.

3.Using effective method of farming such as irrigation, tillage and draining systems.

4.Combating weeds by using herbicides instead of cutlasses and hoes.

5.Plant protection from pests and disease to improve yield.

6.Putting more land under use by motivating and formulation policies that will get more people to be involved in farming.

7.Practicing mechanised farming to obtain high yield. Tractors and modern farm implement to be adopted instead of manual farming.

8.Conservation of land to keep and maintain soil fertility. Soil erosion should be prevented, bush burning should be avoided while mulching and crop rotation should be encouraged.

9.Use of correct agricultural practices such as removing weeds regularly, giving adequate spacing and planting at the right time will improve crop yield.

(b) Causes of Wastage

Reasons why crops are wasted annually on farms include the following:

1.Late harvesting of crops: some crops are over ripe, rot and fall off due to lateness in harvesting.

2.Bad harvesting techniques and incomplete harvesting. Harvest should be invested on and used. Man may skip maize harvest and such maize may be wasted.

3.Delay in transporting crops which make some drops to rot.

4.Lack of good storage facilities; good barns and storage facilities should be made available. If harvested crops are not properly stored wastage will occur.

5.Infections of farm produce by fungi, insects and vermin due to inefficient storage method.

6.The decay of some stored crops caused moisture, especially when they are not properly stored e.g. groundnut, maize and rice.

7.Lack of good roads and good means of transportation for carrying farm to the market or urban centres.

8.Poor method of preservation of some farm produce like tomatoes, carrots, vegetable and other perishable crops.

(c) Methods of Preserving and Storing Food

The methods commonly used in preservation and storage of foods include the following:

1.Drying: food items such as meat and fish can be dried to preserve food and prevent damage. Drying remove water from food and prevent growth of organism that can cause decay.

2.Salting: common salt is added to fish and meat. Salt kills the bacteria by high osmosis pressure.

3.Refrigerating/ freezing: keeping food at low temperature prevents bacteria growth. Meat, fish and vegetables are preserves in this way.

4.Smoking: this removes water from food and prevents growth of microbes on food. Microbes are killed by poisonous substances such as phenols, present in the smoke.

5.Canning: if the food is sealed and air excluded, growth of micro organisms will be impossible. High temperature kills the microbes and kills the microbes and keeps the food.

6.Chemicals: the application of preservatives and protective chemicals on the food keep pests away and also prevents bacteria and fungi from growing on the food, thereby preventing decay.

7.Pasteurisation: it is special method of preserving milk. Milk is pasteurised by heating to 72% for 15 seconds and then cooled rapidly. This destroys micro organisms, thereby preventing the milk from becoming sour very quickly.

Other methods of food preservation are fermentation and radiation.


Pest Control or Pollution?

Pest control has become a difficult issue for farmers because of its potential environmental impact. Although the insecticide being sprayed on this potato field will eliminate a generation of Colorado potato beetles, it may also contaminate local food and water sources.


1.List three dangers of inadequate food supply to the population.

2.State four ways of improving crop yield.

3.State five causes of crop wastage

4.List seven method of food preservation

Population Growth and Food Supply

Population can be defined as the total number of organism of the same species living in a habitat over a period of time. Food supply affects population growth both positively and negatively, based on availability or unavailability of food in a habitat.

If food is adequately available organism will be well fed, give birth to new ones; death rate reduces and population rises. When there is inadequate supply of food, the organism is malnourished, there is competition for the limited food, birth rate reduces, death rate increases and there is a decline in population of the organism. The number of organism migrating out of the habitat increases and cannibalism may set in.

Factors affecting population growth include the following:

1.Reproduction (birth rate)

2.Migration (movement of organism)

3.Death (death rate)

4.Availability of food

5.Availability of space

6.Availability of water

7.Natural disaster




Experiment to Demonstrate Effect of Food on Population

Aim: To show the effect of food on mice population.

Method: Some mice or rodents are kept it two cages. Those in cage 1 are provided with a lot of food and water at the beginning of the experiment. Those in the second cage are supplied with enough food and water continually. The mice left for some time.

Observation: The number of mice continues to increase in the cage with food continuous supplies of food. The population of mice in the cage with food supplied only once will increase for a while when there is no food most of them start to die.

Conclusion: The population of mice tends to increase when there is plenty of food, while their population tends to decrease when there is no food.



1.Define population.

2.State three factors that influence population of an habitat.

3.List three effects of inadequate food supply on population.

4.Describe an experiment that shows the effect of food supply on population.

Relationship between Availability of Food and Human Population (Effects of Storage)

Malthusian hypothesis that human population increases by geometric progression while food increases in arithmetic progression, is an indication that relationship exists between population and food supply. At a point therefore, population will outgrow the supply of food and population growth will stop at one point. Malnutrition, hunger and possibly death will follow to reduce the population to the level the food can cater for.


Starving Children in Niger

Due to climate, drought, poor agricultural planning, political instability, war, and the mismanagement of natural resources, there were about 820 million undernourished people in the developing world in 2006. Only a small percentage of hunger deaths are caused by starvation. Most hunger-related deaths are the result of chronic malnutrition, which weakens the body’s ability to fight diseases. In 2003, almost 16,000 children were dying from hunger-related causes each day.

Effects of Food Storage

Naturally, some crops are meant to grow in wet season while some few are grown in the dry season. If there is no good storage facilities, distribution of food across the season will be difficult; as there would be a period of plenty of food and another period of food shortage. To strike a balance, storage facilities will make equitable distribution of food and food will be available in required quantities at all seasons. Advantages of food storage include the following:

1.Provision of employment opportunities i.e. to workers in processing industries.

2.Provision of adequate food supply during period of war and natural disaster.

3.Stabilisation of food prices at all season. Equitable distribution of food will prevent unnecessary high demand for food at any time which may lead to like in prices of food.

4.It ensures economic use of food by preventing spoilage at time of plenty and adequate supply of food at off-harvest period.

5.Provision of foreign exchange to improve the economy of the nation. Food can be used as aids to countries in need as love and donations.



1.Name five crops that are produced during the wet season but are scarce during the dry season.

2.State two needs for food storage.

3.State four importance of food storage.


Agriculture in Iraq

Agriculture, an important part of the Iraqi economy, became even more essential after the United Nations (UN) imposed trade sanctions on the country in 1990, following Iraq’s invasion of Kuwait. Iraqi farmers grow grains, dates, grapes, figs, and other crops, while nomadic and seminomadic Iraqi herders raise livestock. Yet before the UN trade embargo, Iraq had imported approximately 70 percent of its food. This photograph shows an Iraqi farmer bagging grain.

Government Efforts to Increase Food Production

Many African countries has embarked on gigantic agricultural development programmes that failed

Because of undefined government policies, absence of planning, lack of skilled and experienced personnel and inadequate provision of funds by the government.

In Nigeria, huge finance invested in various governments’ agricultural programmes (such as Operation Feed the Nation and Green Revolution) was grossly mismanaged. Gross financial management has also crippled many of the River Basin Authorities established by the Federal Government to boost agricultural production.

Factors that adversely affect food production include:

1.Unfavourable climatic conditions e.g. drought;

2.Lack of improved varieties of plant and livestock.

3.Conservative attitude of local farmers

4.Inability of many farmers to use modern farming techniques and;

5.Outbreaks of insect pest and diseases.

Government should do the following to aid crop production

1.Provision of irrigation system to supply water for planting at all season.

2.Provision of modern farming equipment to replace manual clearing equipment used by farmer.

3.Provision of good roads and other infrastructure that can aid food production, movement and storage.

4.Fertilizer should be made available at reasonable cost to farmers to improve soil fertility and boost crop production.

5.Training of local farmers in modern day farming to improve their skills.



1.List three agricultural programmes established by the government to boast food production.

2.State three factors that hinders food production.

3.State four ways by which the government can improve food in Nigeria.

4.(a)List ten method of food preservation. (b) Discuss any two methods of food preservation.

5.(a)State any five environmental factors that affect crop production. (b) State any five ways by which farm crops are wasted.

6.(a) list three major consequences of food shortage in the world growing population. (b) Describe an experiment to show the effects of food supply on population

7.(a) State five causes of crop wastage. (b) State four ways of improving crop yield and discuss any one of them.

8.(a) Name three agricultural programmes aimed at increasing food production. (b) State five ways by which government can improve food production in Nigeria.







  1. Micro-organisms in Air and Water

(i) Group of Micro-organisms: Bacteria, Viruses, Some algae, Protozoa, Fungi

(ii) The Concept of Culturing

  1. Identification of Micro-organisms in (i) Air (ii) Pond Water (iii) River (iv) The Concept of Culturing
  2. Micro-organisms in Our Bodies and Food
  3. Carriers of Micro-organisms: Examples, Location of the Micro-organism in Carriers and Types of Micro-organism

Micro Organisms in Air and Water

Introduction: Micro-organisms are very tiny living organisms are also known as microbes.


T-Lymphocyte Infected With HIV

Human immunodeficiency virus (HIV) is the cause of acquired immunodeficiency syndrome (AIDS). By infecting CD4 T-lymphocytes, a type of white blood cell, HIV weakens the immune system and leaves the infected individual open to deadly infections. The viruses gain access to a T-lymphocyte by attaching to CD4 proteins on the outer surface of the cell membrane.


Anthony Van Leeuwenhoek (1632 – 1733) was the first scientist to discover microbes with his newly invented microscope.

Micro-organisms are dreaded as disease causing agents (germs). However, many microbes are of great benefits to man e.g. saprophytic microbes that bring about decay of organic matter. Those microbes that affect man negatively are mainly the parasitic ones which are called pathogem.

Micro-organisms are found everywhere – in the air, water, soil, in our food, on our food, on surfaces of objects, and on and inside living organisms, on our bodies, inside of our bodies and on our clothes in shut, anywhere everywhere.

  1. Groups of Micro-organisms

Microbes are very many and are grouped as follows:

(i) Bacteria

(ii) Viruses

(iii) Some algae

(iv) Protozoa

(v) Some fungi

Most microbes are unicellular but some fungi and algae are multi-cellular. Several microbes survive adverse conditions of temperature or humidity by forming spaces the within the cell. On the return of favourable condition of the spores are released carried in the air and on landing on suitable substrate grow and produce more spores.


Hepatitis B Virus

The hepatitis B virus (HBV) causes inflammation of the liver. The virus is recognizable under magnification by the round, infectious “Dane particles” accompanied by tube-shaped, empty viral envelopes. Symptoms of hepatitis B infection include jaundice and a flulike illness, while chronic infection can lead to serious problems such as cirrhosis and cancer of the liver.

  1. Bacteria

Bacteria can be seen with the use of a light microscope. It has a simple structure. It is unicellular. It is a prokaryotic cell i.e. it does not have a true nucleus. Heredity materials are contained in a strand of DNA (Deoxyribose nucleic acid) inside the cell.

Types of Bacteria

Bacteria can be described based on the following:

1.Oxygen requirement


3.Gram’s staining technique

  1. Based on oxygen requirement
  • Aerobic Bacteria: This group of Bacteria uses oxygen in respiration e.g. vibrio cholerae.
  • Obligate anaerobes: This group of bacteria do not utilize oxygen in respiration e.g. putrifying bacteria.
  • Facultative anaerobes: These are bacteria that can exist in two states e. they can use oxygen and they can also do without oxygen.
  1. Based on shape
  • Cocci:- This group are round in shape.
  • Bacilli:- They have rod-like shape.
  • Spirillae:- These are spiral in shape.
  • Vibrios:- They are comma shaped.
  • Flagellated Spirochaetes:- A number of bacteria have whip-like structure called flagella that effect their movement.


Types of Bacteria

  1. Based on Gram’s staining technique
  • Gram positive bacteria: retains the purple/violet stain in its peptidoglycan (a large structural molecule found in the bacteria cell wall)
  • Gram negative bacteria: loses or do not retain the purple stain in the cells

Bacteria can be the  cause of a number of plant and animal diseases.

(a) Plant diseases caused by bacteria e.g. web blight in cowpeas, black arm in cotton, etc.

(b) Animal diseases caused by bacteria e.g. leprosy, lockjaw, cholera, etc.


Anatomy of a Simple Bacterium

Bacteria cells typically are surrounded by a rigid, protective cell wall. The cell membrane, also called the plasma membrane, regulates passage of materials into and out of the cytoplasm, the semi-fluid that fills the cell. The DNA, located in the nucleoid region, contains the genetic information for the cell. Ribosomes carry out protein synthesis. Many baceteria contain a pilus (plural pili), a structure that extends out of the cell to transfer DNA to another bacterium. The flagellum, found in numerous species, is used for locomotion. Some bacteria contain a plasmid, a small chromososme with extra genes. Others have a capsule, a sticky substance external to the cell wall that protects bacteria from attack by white blood cells. Mesosomes were formerly thought to be structures with unknown functions, but now are know to be artifacts created when cells are prepared for viewing with electron microscopes.

  1. Viruses

They are unicellular in nature, without nucleus, cytoplasm and cell membrane. Smaller than bacteria and can only be seen under electron microscope. Virus lack life. Thus it cannot respire nor carry out metabolism. They can only survive inside living cells.

Types of Viruses

Viruses can be grouped based on:

1.Type of nucleic acid (DNA/RNA)

2.Nature of Protein coat

  1. Based on type nucleic acid
  • Adenovirus, Herpesvirus (DNA)
  • Picornavirus, Togavirus, Orthomyxovirus, Paramyxovirus, Coronavirus (RNA)
  1. Based on nature of protein coat
  • Adenovirus, Herpesvirus, Picornavirus, Togavirus (icosahedral in nature – i.e a polygon with 20 faces and 12 corners)
  • Orthomyxovirus, Paramyxovirus, Coronavirus (helical in nature)


  1. Algae

They are mainly free-living microscopic plants. They survive in a wide range of habits such as wet soil, fresh water, sea etc. they have chlorophyll to a number of other pigments giving rise to green algae, brown algae, blue/green algae etc. examples of algae are: Sprirogyra, volvox, chlamy domonas,nostoc, Diatoms etc.

  1. Protozoa

These are unicellular microscopic animals. They are found in damp soil and water. Some of them are parasitic while others live freely in their habit. Examples of parasitic protozoa are: Trypanosome, plasmodium etc. examples of free-living Protozoa are: Amoeba, Paramecium etc. parasitic protozoans are pathogens that cause disease like Malaria, sleeping sickness, Bilharziasis etc.

  1. Fungi

These are non-green simple plants. They feed Saprophytically or parasitically. Saprophytic fungi such as mucor, yeast, penicilium are useful to man. Parasitic fungi do cause diseases which are unpleasant to man. Example of animal diseases caused by fungi is: Ringworm, Athelet’s foot, mouth thrush, candidiases etc. Plant diseases caused by parasitic fungi are: mildews, spots, wild, blights and Rots.

The Concept of Culturing

Culturing is a technique of growing micro-organisms in the laboratory for the studying the microbes.

The process has to do with:

1.Preparing a sterile medium



4.Examining micro-organism in the medium.

While bacteria, fungi and algae can be grown in test tubes and Petri dishes in culture media, viruses cannot be grown. They can only grow and multiple inside living cells of an organism.

Through Tissue culture, living tissues and cells of multi-cellular organism are cultured in appropriate media and studied. To carry out studies involving viruses, viruses are cultured in the laboratory by injecting the virus into the fertilized bird’s egg e.g. egg of duck.

On the culture medium, micro-organisms occur as colonies. Colonies of micro-organism do clump together in large number of organism of the same kind. Colour, appearance other characteristics of the colonies enable the investigator to identify and differentiate microbes in a culture medium.



1 (a) What are Micro-organism?

(b) List the important groups, giving examples of each group.

2 (a) Expalin the concept of culturing.

(b) What steps will you take in preparing a culture solution and state precautions in preparing it.

(c) Identify sources of samples for culturing.

Identification of Micro-organisms in the Air, Pond Water, River, Stream

1.Micro-organisms in our bodies and food.

2.Carries of Micro-organisms, examples, location of the Micro-organisms in carries.

3.Types of micro-organisms.

Micro-organisms in the Air

Micro-organisms commonly found in the air are: Bacteria, Virus and Fungi. These microbes do not grow in the air but are present as spores in dust and water droplets in the air. These  spores are light and easily dispersed by air movement. When these spores land on suitable substrate, they germinate, multiply and produce more spores. Micro-organisms found in the air and examples:

(a) Bacteria: Examples – Pneumococci, Staphylococci, Streptococci, Bacillus anthracis, which causes anthrax in herbivores.

(b) Virus: examples – Influenza, Polio virus, common cold virus, measles virus.

(c) Fungi: Examples – Sacromyces (yeast), Rhizopus nigricans (bread mould), Penicillium (blue-green mould) Aspergillus etc.


Bacterial Cultures

Colonies of the bacteria known as Escherichia coli (larger, pink) and Proteus vulgaris (smaller, brown) grow side by side in this petri dish culture. Under normal circumstances both of these bacteria harmlessly inhabit the human intestines and aid in digestion, but can become pathogenic and cause infections, such as urinary tract infections. Scientists and doctors grow cultures of bacteria and study their characteristics in order to learn about bacterial diseases and disease prevention.

Micro-organisms in Water

Micro organisms found in water are commonly known as plankton. Aquatic environment, unlike atmosphere are rich in organic and inorganic nutrients. They can be found in all types of water habitat viz: wells, ponds, lakes, streams, rivers and seas.

All microbes found in water can be grouped into three as follows:

1.Natural water micro-organisms: these are microbes that are naturally found in aquatic habitats.

2.Soil micro organism ( washed into the surrounding water bodies during heavy rains)

3.Sewage micro-organisms



Bacteria, included within the kingdom Prokaryotae, are single-celled organisms lacking a well-defined internal cellular organization. The bacterium Leptospirilla ichterohemorrhagiae, pictured here, exhibits the spirochete, or spiral, structure characteristic of many of the 1600 species of bacteria.

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Micro-organisms in Water and their Examples

1.Bacteria: Examples – aquatic species of coccus, Baccillus, Pseudomonas, Azobacter, Thiobacillus, Sarcinina, spirillum, Micrococcus, Vibro and Spirochaeta. These bacteria are either heterotrophic, autotrophic and chemotrophic.

2.Blue green algae: Examples; oscillatoria, nostoc, anabaena,

3.Protists: These are autotrophic diatoms e.g. chlamydomonas, cholera and some species of euglena as well as heterotrophic amoeba and paramecium.

4.Algae: These are located close to the shore of where they form thick green floating mesh e.g. spirogyra, volvox etc. Algae arte major part of primary producers in the aquatic habitat since they contain chlorophyll and can photosynthesis.

Micro-organisms in Our Bodies

Various parts of human body such as the skin, hair, mouths, nose, ears, under the nails, our teeth etc to different micro-organisms as well as serve as entrance for these micro-organisms into our bodies.

Millions of micro-organisms living inside and outside the human body. These microbes are non-pathogenic. They are regarded as the normal micro flora which plays importance role in the body.

This normal micro flora prevents pathogen from invading the body as well as secretes certain substances that inhibits or kills some other pathogens.  Weakened immune systems , indiscriminate use of antibiotics, unhygienic practices like smoking and intake of alcohol malnutrition, stress etc could make non-pathogen to become pathogenic harmful to the body as the normal micro flora become disturbed.

Pathogens harm the body by using up the hosts’ nutrients thereby starving the tissue of the host.

Through their actions they damage tissues of the affected part of the host as well as produce toxins that negatively affect the functioning of particular organs or body systems of the individual.


Anthrax Bacteria

An electron micrograph shows a cluster of bacteria, Bacillus anthracis, in a capillary of a lung. The bacteria cause anthrax, a disease in humans and animals that can result in death. Anthrax can be cured when treated early with antibiotics.

Entry of Micro-organisms into Our Body

Micro-organisms enter the human body through:

1.Buccal cavity: The food we eat and the water we drink. Such pathogen cause air borne infection like tuberculosis cause by mycobacterium tuberculosis

2.The nose: Air we breathe in, into the respiratory system such virus normally cause cold.

3.Damaged skin: Cuts or bruises on the skin into the blood stream Telamus. fungi infection, leading to ringworm on the head, foot etc.

4.Oesophagus: Contaminated food or drinking water.

5.Direct contact: Skin surfaces e.g. fungal infections which result in ringworm of the head and foot.

Micro-organisms in Food

The physical and chemical properties of any food determine the type of micro-organisms that will grow and reproduce. When micro-organisms or their spores get in contact with food, such food gets contaminated and when consumed man can have adverse effect on the individual.

Carriers of Micro-organisms

Apart from the various means through which microbes get into our body already discussed, there are certain organisms that carry micro-organisms that can affect man negatively about. These organisms are called Careers are usually insects and mammals. The hairy nature of the insect body traps the microbes and gets carried from place to place. The natural habitats of these insects include latrines, food stores, dung hills and other similar places where microbes abound. The careers pick up the pathogens and bring them to exposed human food. As they land on these exposed food to feed on them, the microbes are transferred to the food which could be eaten by man and consequently bring about infection and diseases. These careers are called Vectors. The pathogen neither grow nor affect them adversely hence, they are called Vectors. Vectors are primary to the pathogen while man is the secondary Host.



1.What are careers? Give two examples.

2.State the habitat of the career named above.


Streptococcus Bacteria

This scanning electron micrograph shows disease-causing Streptococcus bacteria, commonly found in the human mouth, throat, respiratory tract, bloodstream, and wounds. Often airborne in hospitals, schools, and other public places, Streptococcus bacteria are responsible for infections such as strep throat, scarlet fever, and some types of pneumonia.

Location of Micro-organisms in Carriers

Organisms that carry micro-organisms are called vectors. Diseases caused by a carrier do not affect the vector that carries them.

The micro-organism found in vector lives in them temporarily for the purpose of developing to the stage where they can effectively infect man. Thus the pathogens have two hosts. This phenomenon is killed alternation of hosts. The vector is the primary host while man is the secondary host of the pathogen. Mosquitoes, Tsetse fly are examples of vectors of microorganism that do not develop inside the housefly. Instead the body of the housefly’s body “collects” micro-organisms as it perches on exposed human food to feed on it, the microbes (bacteria) falls off its body onto the food which causes disease unto man when contaminated food is eaten.

Through biting and sucking man’s blood, Anopheles Mosquito transmits a protozoan – plasmodium into mans blood causing disease – malaria. The pathogen is in the gut of the insect and as it feeds on the blood of man, it deposits it into man.



1.Define the following terms: (i) natural microflora (ii) pathogen (iii) careers (iv) vectors

2.Name and describe the two methods by which pathogens are carried from place to place.

3.List the important groups of micro-organisms and give one example from the group.

4.What is culture?

5.Outline the steps you will take in preparing a culture solution.

6.(a) What do you understand by micro-organisms? (b) Describe how micro-organisms enter our bodies with examples and steps preventing them. (c) List the groups of micro-organism with examples.

7.(a) List micro-organisms found in water with examples. (b) Micro-organism in 2a can be grouped into 3, name these groups with short explanations. (c) A group of aquatic micro organisms are known as primary producers explain.

8.(a) What is culture? (b) What steps are entails in preparing a culture solution (c) Outline precautions to observe in preparing a culture solution.

9.(a) Describe an experiment to show that atmospheric Air contains micor-organisms. (b) What are the functions of natural normal micrflora in and on human body? (c) List two insects and three mammalian vectors, stating the following for each organism: (i) micro-organisms (ii) Disease caused (iii) possible control of spread

10.Define the following terms: (a) natural microflora (ii) pathogen (iii) careers (iv) vectors (b) Write short notes on the importance of micro-organism to man in the area of (i) medicine (ii) agriculture



1.Preparation of culture solution.

2.Examine the presence of microbes in air, water, saliva, under nail.

3.Classification of bacteria using different criteria.








1.Meaning of Micro-organisms

2.Types of Micro-organisms

3.Growth of Micro-organisms: Ways of Measuring the Growth of Microorganisms

4.Beneficial Effects of Micro-organisms in Nature, Medicine and Industries

5.Harmful Effects of Some Microbes


Meaning of Micro-organisms

Micro-organisms are very small living things which are normally not visible to the naked eye but can be seen with the help of a microscope.

Types of Micro-organisms

Micro-organisms include the following:

(i) All Viruses e.g. Polio virus, Smallpox virus, etc.

(ii) All bacteria e.g. Salmonella, Clostridium, Treponema, Escherichia coli, etc.

(iii) All protozoans e.g. Plasmodium, Trypanosoma, etc.

(iv) Some fungi e.g. Rhizopus (mould) and Yeast (e.g. Saccharomycetes).

(v) Some algae e.g. diatoms, dinoflagelletes, etc.

(vi) Blue-green algae e.g. Nostoc

Micro-organisms live everywhere, in water, air, soil, inside and outside of plants and animals including human beings. There are many more microorganisms than visible plants and animals in the world. They may have beneficial or harmful effects. Micro-organisms that cause disease are referred to as pathogens and are usually parasitic.


Anthrax Bacteria

An electron micrograph shows a cluster of bacteria, Bacillus anthracis, in a capillary of a lung. The bacteria cause anthrax, a disease in humans and animals that can result in death. Anthrax can be cured when treated early with antibiotics.

Growth of Micro-organisms

Culturing is the growing of micro-organisms in prepared media in the laboratory. The prepared medium is called the ‘culture medium’. Bacteria, fungi and algae grow easily in test-tubes, flasks or Petri dishes of culture media. Virus on the other hand, can only grow and multiply inside living cells, so they cannot be grown in a culture medium.

Micro-organisms are able to increase in size and multiply in number of cells. The growth of micro-organisms is measured based on increase in population size rather than increase in cell size. Under favourable conditions (food, adequate temperature and humidity) micro-organisms reproduce asexually by binary fission. Generation time varies from species to species e.g. rapidly growing species like Escherichia coli can divide every 30 minutes.

Measurement of the Growth of Micro-organisms

Two methods are used to measure the growth of micro-organisms:

(i) First Method: This involves inoculating a bacterial sample into a nutrient broth. As the bacterial population increases, the clear liquid medium becomes cloudy/turbid. Increase in turbidity indicates an increase in number of bacterial cells. Turbidity can be measured using a spectrophotometer. Thus by measuring the turbidity of a bacterial culture in nutrient broth at regular intervals, the growth of a bacterial population can be measured.

(ii) Second Method: This involves taking small samples of bacteria from a nutrient broth at regular intervals of time and diluting the samples several times. Each diluted sample is then inoculated onto a nutrient agar medium in a petri dish and incubated. The number of colonies formed in each petri dish is counted and this indicates the number of living bacterial cells in the diluted sample. From this, the actual number of bacteria in the original sample can be calculated.



1.Mention five microorganisms.

2.How is the growth of microorganisms measured?

3.Describe two ways of growing microbes in the laboratory.

Bacterium Showing Flagella

Although many forms of bacteria are not capable of independent movement, species such as the Salmonella bacterium pictured here can move by means of fine threadlike projections called flagella. The arrangement of flagella across the surface of the bacterium differs from species to species; they can be present at the ends of the bacterium or all across the body surface. Forward movement is accomplished either by a tumbling motion or in a forward manner without tumbling.

Beneficial Effects of Micro-organisms in Nature

(i) Bacteria in the large intestine of man synthesize the vitamin K that is needed.

(ii) Yeasts are used in baking and preparation of alcoholic drinks. Yeasts are an important source of vitamin B.

(iii) Some bacteria are used in curdling of milk, brewing of wine and in butter and cheese making.

(iv) It is used in the production of antibiotics e.g. penicillin from the mould called penicillium.

(v) Saprophytic micro-organisms decompose sewage into harmless inorganic compounds.

(vi) Most decomposers are micro-organisms and they help to maintain soil fertility.

(vii) Some bacteria living in the rumen of ruminants like sheep, goat, cattle help to digest cellulose in their food (grasses/vegetation).

(viii) Micro-organisms help in maintaining some cycles in nature e.g. the nitrogen cycle and carbon cycle. They also help in recycling phosphates and sulphate.



Name two beneficial microorganisms and state their benefits to man.

Harmful Effects of Micro-organisms

(i) Most diseases in animals and plants are caused by micro-organisms especially bacteria, viruses and protozoans.

(ii) Huge amounts of food are spoiled annually by saprophytic fungi and bacteria.

(iii) They also cause deterioration/damage to materials such as paper, wood, cotton, leather, etc.

(iv) Micro-organisms can also cause the death of plants and animals.


Cholera Bacterium

An electron micrograph shows the bacterium Vibrio cholerae, which can cause cholera, a serious infectious disease in humans. The bacterium produces a toxin that causes the small intestine to secrete large amounts of fluid, leading to diarrhea, vomiting, muscle cramps, and sometimes death. A vaccine made from dead bacteria offers partial protection.

Disease-causing Micro-Organisms

Micro-organisms are spread through the following:

(i) Air: Dust and water droplets in our air contain micro-organisms such as polio virus, measles virus, pox virus, common cold virus, Pneumococci

(a bacteria), Pencillium (a fungus), etc.

(ii) Water: Bacteria found in water include Bacillus, Pseudomonas, Vibrio, Azotobacter, Coliform micro-organisms (e.g. Escherichia coli, Vibro cholerae, Salmonella typhi), etc. Blue-green algae found in water include Nostoc,Anabaena and Oscillatoria.Protists in water include Chlamydomonas, Euglena,Amoeba, etc. Algae include Spirogyra, Volvox. Fungi include moulds and mildews.

(iii) Food: Most micro-organisms in food get in through faeces, dirty utensils and equipment, unhygienic habits and vectors like flies and cockroaches. Examples are Shigella sp, Salmonella enteriditis, Aspergillus flavus, etc.

(iv) Animal vectors or carriers.

(v) Personal or direct skin contact with a sufferer.

Disease-causing micro-organisms can enter the body through body openings like the mouth, nose or reproductive opening, through wounds, through bites of other animals and through blood transfusions.

Some important diseases, their causative micro-organisms, mode of transmission, host and symptoms are outlined in the following tables.

Air-borne Diseases

Disease Causative

organism Mode of

transmission Host Major symptoms

  1. Common cold Virus Airborne Man High fever,

headache running


  1. Chicken pox Pox virus Airborne Man Itchy skin rash
  2. Measles Paramyxo-virus Airborne and

close contact Children High fever, skin rashes,

headache, head

cold, cough, body pain.

  1. Pneumonia Bacteria Air Man, birds,

pigs, cows High fever, difficult

breathing and cough

  1. Tuberculosis Myco bacterium


(bacterium) Airborne,

food Man, cow Persistent dry cough

and profuse sweating

at night.

  1. Meningitis Meningo coccus

(Bacterium) Airborne Man High fever, headache,

vomiting and stiffness

of the neck.


Streptococcus Bacteria

This scanning electron micrograph shows disease-causing Streptococcus bacteria, commonly found in the human mouth, throat, respiratory tract, bloodstream, and wounds. Often airborne in hospitals, schools, and other public places, Streptococcus bacteria are responsible for infections such as strep throat, scarlet fever, and some types of pneumonia.

Food and Water-borne Diseases

Disease Causative organism Mode of transmission Host Major symptoms

  1. Typhoid Salmonella typhi

(bacteria) Contaminated

food and water Man High temperature,

followed by

bloody diarrhea

  1. Cholera Vibro cholerae

(bacterium) Food and water Man Vomiting and


  1. Food

poisoning Salmonella sp.

(bacteria) Infected meat,

Poultry, eggs, milk and

contaminated food Man Diarrhea and


  1. Amoebic

dysentery Entamoeba histolytica

(protozoan) Contaminated food

and water Man Abdominal pain,

and diarrhoea

  1. Poliomyelitis


paralysis) Picornavirus

(virus) Infected food and

water, direct contact Children High fever, headache

nausea, fits and

stiffness of limbs



Bacteria, included within the kingdom Prokaryotae, are single-celled organisms lacking a well-defined internal cellular organization. The bacterium Leptospirilla ichterohemorrhagiae, pictured here, exhibits the spirochete, or spiral, structure characteristic of many of the 1600 species of bacteria.

Vector-borne Diseases

Disease Causative organism Mode of transmission Host Major symptoms

  1. Malaria Plasmodium sp.

(protozoan) Bite of infected

female Anopheles

mosquito Man High fever, shivering

and sweating

  1. Sleeping sickness

(Trypanosomiasis) Trypanosom


(protozoan) Tsetse fly bite Man and


animals Fever, headache,


drowsiness and

un- controllable sleep

  1. Yellow fever Arbovirus Bite of infected

Aedes mosquito Man High fever, headache,

backache followed by

low body temperature

and jaundice

  1. Plague Bacterium Bite of infected

Rat flea Man Shivering fever, cough

and difficult breathing

  1. River blindness

(onchocerciasis) Onchocerca

volvolus Bite of infected

black fly Man Severe headache,

high fever and

gradual blindness

Diseases Spread by Contacts

Disease Causative organism Mode of transmission Host Major symptoms

  1. Tinea versicolor Dermatophytes Direct skin

contact Man Yellow patches on

chest, neck, face

and back

  1. Athlete’s foot Fungi Direct skin

contact Man Itching, smelly patches

between toes

  1. Gonorrhea Neisseria


(bacterium) Sexual

intercourse Man Inflamed urethra

burning sensation

during urination

and thick yellowish

discharge in male.

In females there may

be pain during

urination, redness

around the urinary

opening and vaginal


  1. Syphilis Treponema


(bacterium) Sexual

intercourse Man A small painless

sore or chancre

on the penis or vulva.

Mild fever, skin rashes,

mouth ulcers and aches

in lymph node regions.

It may lead to abortion,

attack the brain and

cause blindness

and insanity

  1. AIDS Human


virus (HIV) Sexual intercourse,

blood transfusion,

infected sharp


mother to

unborn child Man Susceptibility to all

microbial infections,

high fever, loss of

weight, chronic

diarrhoea, skin rashes,

wasting away of



  1. Mention two disease causing microbes, state the diseases caused, the host, the mode of transmission and the symptoms of the disease.
  2. How do microorganisms gain access into the body?
  3. Describe the stages involved in the growth of inoculated microorganisms (Graphical illustration is important).
  4. (a) What is a venereal disease? (b) Mention four venereal diseases (c) Outline five ways of controlling venereal diseases.
  5. Read up on Towards Better Health.








1.Control of Harmful Micro-organisms

2.Vectors (i) Definition of Vectors (ii) Ways of Controlling Mosquitoes (iii) Ways of Controlling Vectors

3.Student’s Health: Maintenance of Good Health


Control of Harmful Micro-organisms

Better health can be achieved basically by controlling disease-causing micro-organisms and their animal vectors and also by improving health facilities.

Micro-organisms can be controlled in the following ways:

1.Use of High Temperature: This involves sterilization by boiling, autoclaving or heating of food and other products to kill disease causing organisms.

2.Preserving Food by Salting: This is the application of salt in food to kill micro- organisms or render them inactive

3.Uses of Drugs/Antibiotics: Many diseases can be controlled through the use of drugs and antibiotics in order to kill the causative micro- organisms. Fansid is used to kill malaria.

4.Immunization or Rascination: Immunization is the process by which a healthy person is inoculated with a preparation of a mild form of the pathogen.

5.Sterilization by Boiling: Sterilization by boiling is done to kill disease-causing micro-organisms (pathogens) on the objects.

6.Use of Antiseptics: These are chemicals that can kill or inhabit the growth of pathogenic micro-organisms. They are used on cuts, abrasions and wounds on the skin to prevent infection by micro-organisms. Examples of antiseptics are; hydrogen peroxide, Dettol, chlorine water etc.

7.Proper Covering of Food Always: Food should be covered always to prevent contact with vectors of diseases.

8.Quarantine Service: Quarantine service or isolation of infected person or animal for evidence of a disease before he/she or it mixes with general population.

9.Promoting Health Education: This is making people aware and conscious of ways micro-organisms are transmitted and how to prevent them.

10.Personal Hygiene: This includes washing of hand before eating and after eating, after defecating, before preparation of food etc. these practices can help check the spread of pathogenic micro-organisms.

11.Use of Disinfectants: Disinfectants like izal, Lysol etc. may lead to prevent infections.

12.Destruction of Vectors: Vectors such as mosquitoes, black flies etc. can be destroyed to prevent the spread of diseases they cause.

13.Use of ultra-violet radiation to kill bacteria.


Non-living agents that carry micro-organisms from one place to another include air, water and food.

Living agents that carry micro-organisms from place to place are animals. These animals that carry pathogenic (disease causing) micro-organisms are known as vectors.

Examples of vectors are cockroaches, fleas, mosquitoes, tsetse-flies, black flies, house flies, bed-bugs, ticks, rats, dogs, cats, etc. Vectors may transmit micro-organisms from place to place or person to person either mechanically or biologically.

(a) Mechanical Method: The vectors carry pathogens on various parts of their bodies e.g. legs, wings, mouthparts, hairs, etc. The pathogens do not grow or multiply on the body of the vectors. Pathogens carried in this way include Salmonella typhi, Vibro cholerae and Entamoeba histolytica.

(b) Biological Method: The vector in this case becomes infected with the pathogen when it feeds on the body fluid of an infected person or animal. The pathogen develops and multiplies in the body of the vector which then infects a healthy person when it goes to feed. Thus part of the pathogen’s life cycle takes place in the body of the vector. Examples of such vectors and the pathogen they carry are;

(i) Anopheles mosquito (female) carries plasmodium (protozoan) that causes malaria.

(ii) Tsetse fly carries Trypanosome (protozoan) which causes sleeping sickness (Trypanosomiasis).

(iii) Aedes mosquito carries a virus that causes yellow fever/dengue fever.



Control of Mosquitoes

Mosquitoes can be controlled in the following ways:

1.Draining of swamps: This is done to destroy the breeding ground of mosquitoes.

2.Clearing bushes around houses: This reduces hiding places for the adult mosquitoes.

3.Sleeping in rooms protected by mosquito nets: This help to check the occurrence of mosquito bites.

4.Spraying oil in stagnant water: This is to reduce the surface tension of water and prevent larval stages from breathing.

5.Using insect repellants for the body

6.Use of drugs i.e. to cure/control malaria fever e.g. chloroquine

7.Burying broken pots and empty cans

Control of Vectors

Vectors can be controlled by;

1.Killing the vectors e.g. by spraying with insecticides, use of traps and poisons for rats, etc.

2.Use of larvicides to kill larval stages.

3.Clearing bushes around houses.

4.Destruction of breeding spots e.g. stagnant water should be drained to prevent mosquitoes from breeding.

5.Use of drugs to kill the micro-organism in the host.

6.Keeping the environment clean etc.

Student’s Health: Maintenance of Good Health

Maintaining the health of students and the people in a community is the responsibility of the individuals, the community, the government and health organization. Ways of maintaining good public health include;

1.Proper observance of personal hygiene. Keep yourself and your environment clean.

2.Proper refuse disposal e.g. burning in incinerators, burying in sanitary landfills, etc.

3.Proper sewage disposal e.g. use of pit toilets and water-closet toilets.

4.Protection of water supply by boiling, filtration, addition of chlorine, storage in clean containers, etc.

5.Protection of food by keeping them in clean containers, boiling or cooking properly before eating, washing of fruits, vegetables and hands before eating, etc.

6.Health organizations such as United Nations Children’s Education Fund (UNICEF), World Health Organization (WHO), International Red Cross Society, etc. help to maintain the health of people in a country through their corporate activities.


1.Define the term ‘vector’

2.Enumerate four vectors, the pathogens they carry and the diseases caused by these pathogens

3.State three ways by which vectors can be controlled

Ways of Maintaining Good Health in the Community

  1. Refuse Disposal: Refuse is solid waste materials discharged through human activities from homes and industries into the environment. When these are dumped recklessly, they create bad odour and provide breeding ground for vectors and pathogens.

Refuse disposal can be done through:

(i) Provision of dust bin in strategic locations.

(ii) Burning refuse in incinerators.

(iii) Dumping them in isolated areas far from human inhabitation.

(iv) Burying in a sanitary land fill.

  1. Sewage Disposal: These are liquid waste materials discharged from laundries, kitchens, toilets, bathrooms etc.

Sewage disposal can be done through:

(i) Use of pit toilets where faeces and urine are passed into deep pits.

(ii) Use of septic tanks where water is used to flush faeces and urine into a big tank dug in the ground.

(iii) Community treatment process where sewage from various homes are collected and treated before being discharged into oceans and rivers.

  1. Protection of water: Water should be protected to check with incidents of water-borne diseases like cholera, salmonellosis, etc.

This can be done by:

Adding alum to water.

(i) Chlorination: Adding of chlorine water.

(ii) Storing water in clean containers.

(iii) Filtering of water on settling/coding.

  1. Protection of food: Both raw and cooked food should be kept properly to avoid the outbreak of food poisoning. This can be achieved by:

(i) Refrigeration: Keeping food in refrigerators.

(ii) Proper cooking/boiling of food.

(iii) Washing of hands before and after eating.

(iv) There should be inspection of food meant for public consumption.

(v) Preservation of food by canning.

(vi) Avoid expression of food to flies and other micro-organisms.

(vii) Keep the environment where food is prepared clean.

  1. Control of diseases: Individuals can control disease by:

(i) Living in a clean environment.

(ii) Eating good and balanced diet.

(iii) Wearing good and clean clothes.

(iv) Cleaning latrines and urinals with disinfectants.

(v) Exercising regularly.

(vi) Avoiding drug abuse.

(vii) Immunization and vaccination.

  1. Health Organizations: These are corporate (international and local) bodies concerned with the maintenance of good health of the people. International health organizations include:

(i) WHO – World Health Organization.

(ii) UNICEF – United Nations International Children Emergency Fund.

(iii) NMA – Nigeria Medical Association.

(iv) Red Cross Society.

Roles of Health Organizations

World Health Organization (WHO)

This is a specialized division of the United Nations established in 1948 with its headquarters in Geneva, Switzerland. Its major aim is to improve the health of the people in all the countries of the world.

Functions of the World Health Organization (WHO)

1.It helps to set and recommend safe standard for drugs.

2.It helps in maternal and children health care.

3.It assists national health organizations in the control of diseases and vectors of diseases.

4.It publishes medical journals.

5.It helps to provide drugs and vaccines in case of emergency.

6.It co-ordinates research programmes in all fields of health and makes the result known to all member nations.

United Nations Children’s Emergency Fund (UNICEF)

The UNICEF, another special agency of the United Nations was set up to improve the health and welfare of the children all over the world.

Functions of the United Nations Children’s Emergency Fund (UNICEF)

1.To provide for the emergency needs of children in devastated areas.

2.To improve the nutrition of under nourished children.

3.To supply vaccines or equipment to prevent or control diseases that specifically affects children such as whooping cough, diphtheria, poliomyelitis etc.

4.To provide children’s clothing and other needs.

International Red Cross Society

This is concerned with the alleviation of human suffering and the promotion of public health. It was established in the year 1863 in Geneva, Switzerland composed of 25 Swiss citizens who later grew to all around the world.

Functions of the International Red Cross Society

1.In times of war

2.They take proper care of the injured

3.They also provide welfare for the prisoners of war

4.They provide transport for the evacuation of refugees

5.In Time of Peace.

6.They provide the general first-aid to patients.

7.They maintain maternal and child welfare clinics.

8.They provide help to victims of natural disasters such as earthquake, floods, fire etc.

Nigeria Medical Association (NMA)

This is a national body concerned with the maintenance of good health within Nigeria.

Functions of the Nigeria Medical Association (NMA)

1.Advising the government on how to improve the health status of the people.

2.Alerting the nation where there is an outbreak of diseases.

3.Carrying out research into ways of preventing and controlling diseases.

4.Monitoring the recruitment of well-trained doctors in hospitals.


  1. Malaria is one of the most common diseases in the tropics. Explain clearly, how a bite from a mosquito can cause malaria.
  2. Describe the functions of the following health organizations

(a) World Health Organization.

(b) United Nation Children’s Fund (UNICEF)

(c) International Red Cross

  1. Read on Marine Habitat.

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