Biology lesson note for SS2 First 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 SS2 First Term has been provided in detail here on schoolings.org
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 SS2 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 SS2 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 SS2 Biology lesson note for First 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 SS2.
Please note that Biology lesson note for SS2 provided here for First 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.
SS2 Biology Lesson Note (First Term) 2023
FIRST TERM SCHEME OF WORK OF S.S. TWO
WEEK 1 The cells
WEEK 2 The cell structure and functions of cell component
WEEK 3 The cell and its environment, diffusion, osmosis
WEEK 4 Properties and function of the cells
WEEK 5 Cellular Respiration
WEEK 6 Growth (mitosis)
WEEK 7 Irritability/ cell reaction to its environment
WEEK 8 Reproductions (Asexual)
WEEK 9 Sexual Reproductions
WEEK 10 Reproductive Health
THE CELL STRUCTURE AND FUNCTIONS OF CELL COMPONENTS
A cell is the basic structural and functional unit of life.
The cell structure of both plant and animals are composed of protoplasm which can be divided into two main parts
- The cytoplasm is a fluid material that consists of cytoplasmic organelles such as lysosome, golgi bodies, endoplasmic, reticulum e.t.c.
The nucleus is bounded by a nuclear membrane and within the nucleus are:
(i) chromosome (ii) Nucleus
The animal cell addition has centromere while the plant in addition has starch granules, cellulose cell and some plastids (chloroplast).
Similarities Between Animal cell and Plant cell
Both Plant and Animal cells are similar because they posses cytoplasm, cell membrane, endoplasmic reticulum, nuclear membrane. Nucleus, chromosomes, nucleoplasm and nucleolus. They both carryout mitosis in somatic cell and meiosis in reproductive cells..
PLANT CELL ANIMAL CELLS
- Cell has a dead cellulose cell wall hence definite Cell has living cell membrane hence
In shape it can change its shape
- Chloroplast is present Chloroplast absent
- A large central vacuole present Small vacuoles may be present or absent
- Centrioles are absent Centrioles are present
- Cytoplasm is dense and found along the periphery Cytoplasm is dense and granular and
Of the cell fills cell completely
- Food is stored as starch granules Food is stored as glycogen and fat
- Plant cell may be polygonal rectangular or square It is either circular or avoid in shape
Function of cell components
Cell organelles are defined as all the structures outside the nucleus but floating on the cytoplasm. Such materials include endoplasmic reticulum, mitochondrion, lysosome, golgi apparatus e.t.c. all the materials are bounded by cell membrane.
i.All living substances including nucleus are suspended in the semi-fluid cytoplasm
ii.The streaming of the content of the cytoplasm bring about inter change of material between the organelles with the cytoplasm
The cell wall is the non-living outer boundary of the cell made of cellulose. It has tiny pores or its pits through which nutrient pass from one cell to another. Cell wall is absent in animal cell
1.It gives rigidity to the cell and plant as a whole
ii.It allows free passage of material
The cell membrane is a thin and flexible living later that surrounds the entire cytoplasm and separates the cell from neighboring cells.
i.It regulates the movement of substances in and out of the cells
ii.It protects the cytoplasm
iii.It determines the content of the cytoplasm
iv.It forms a barrier between the cell and its surrounding
Endoplasmic reticulum is a system of canals found abundantly in the cytoplasm. It ribosome are attached to it in rough ER and if no ribosome are attached it is called smooth ER.
Rough endoplasmic reticulum
1.They transport metabolic products within cytoplasm between the cytoplasm and nucleus
2.They help in formation of enzymes and protein
3.They help in formation of nuclear membrane during nuclear division
4.They inter connect the organelles of the cell
5.They provide surface for the attachment of ribosome
Smooth endoplasmic reticulum
1.It makes lipid (Fat molecules)
2.The enzymes of the S. ER in the liver detoxificate drugs
These are minute and spherical organelles found in large number attached to endoplasmic reticulum or suspended in the cytoplasm
1.They make proteins by joining amino acids together
2.They are also site for protein synthesis
These are tiny red-shaped bodies or granules in the cytoplasm. They are more concentrated in very active cells such as liver cells.
1.They are center for cellular respiration in which food substances are oxidized to release energy for the activities of the cell
2.It contains enzymes and deoxyribo nucleic acid (DNA). The enzymes carry out oxidative phosphorylation of adenosine diphosphate (ADP) to adenosine triphosphate (ATP)
3.The DNA helps to code the synthesis of protein in mitochondria membrane
These are minute and rounded bodies containing enzymes found in animal cells
1.They destroy worn out part of the cell by discharging enzymes into them thereby clearing the area for new cell to grow
2.Lysosomes discharge enzymes to degenerated tissues causing the breakdown of the cells
These bodies are found as flat tubes of threads. They are absent in mature sperm and red blood cells
1.They help to distribute proteins made by the cell
2.They help in the manufacture of lysosome
3.They help in the formation of membrane of endoplasmic reticulum and production of cellulose of cells of plant
These are usually two small, cylindrical bodies found near the nucleus. The two centrioles are mostly found in animal cells. They are absent in plant except some few algae and fungi
1.They provide spindle fibers to which chromosomes are attached during cell division
2.They help in the formation of cilia and flagella
Chloroplasts only occur in green plants. The organelles called chloroplast contain green pigment called chlorophyll. A chloroplast is surrounded by a membrane. In the leaves chloroplasts are oval or disk-shaped in algae
1.It is the site of photosynthesis where organic foods are synthesized
Vacuoles are found both plant and animal cell. It is bigger in plant. A vacuole is surrounded by a membrane called tonoplast and is filled with water, mineral salt, sugars and pigments called cell sap.
1.The cell sap is osmotic in function
2.It stores nutrients and waste product
3.Sometimes vacuole contain colour pigments called anthocyanin which may blue, purple, yellow, red which give coloruration to flowers
The nuclear membrane permits substances to go in and out of the nucleus. Within the nucleus is a small spherical body called nucleolus and the chromatin materials which condense during cell division into chromosome (hereditary unit). The inside of the nucleus is filled with a semi fluid material called nuclear fluid or nucleoplasm.
The chromosomes are made up of DNA (deoxyribonucleic acid).
1.The nucleus controls the activities of the living cell
2.The nucleus carries chromosomes on which hereditary material (gene) are coded
3.The nucleolus produces several kinds of RNA which are passed of out the nucleus to cytoplasm to manufacture protein
History of cell
In 1665, Robert Hooke, a British scientist examined thin slice of cork tissue under the compound microscope and found that the cork consisted of many neatly arranged little chamber or cavities. Since each chamber was enclosed by walls similar to cell of honey combs, he named the chamber cells.
In 1835, Dujardin, a French biologist, examined thin slice of living plants under much improved microscope and discovered that cells have content. He named the content sarcode, later named protoplasm by Purkinje in 1839 and von Mohl in 1846.
In 1839,Mathias Schleiden was a German botanist discovered that all plants are made up of cells.
In 1839, Theodor, a German zoologist examined bits of animals under a microscope and observed that animals were composed by cells.
In 1839, Schleiden and Theodor Schawann jointly stated what is now known as the cell theory, namely that all living things are made up of cells. After the statement of the cell theory, in 1846, Hugo Von- Mohl fisrt applied the term protoplasm to the the living substances in the cell, the name by which it si still known till today. In 1858 Rudolf Virchow stated that cells come from pre- existing cells.
The cell Theories
1.All living things are made up of a cell or cells
2.The cell is the structural and functional unit of all living things
3.New cells arise from pre-existing cells by cell division
4.There is no life apart from the life of cell
5.All living things are either single cell or a group of unicellular or multicellular
CELL AS A LIVING THING UNIT OF AN ORGANISM
A cell is defined as the basic structural and functional unit of a living organism. In other word, the cell is the simplest, smallest and basic unit of life because it can carryout all life activities
1.The statement that all living things are made of cells was first made by A. Dujardin B. Robert Hooke C. Mathias Schleiden D. Von –Mohl E. Rudolf Virchow
2.The part of a cell that is responsible for protein synthesis is called A. endoplasmic reticulum B.nuclear evelope C.ribosome D.mitochondria E.Golgi bodies
3.Which of these is present in both plant and animal cells? A. cell membrane B.chloroplast C. cellulose D. large E. cell sap.
4.Which of the following statements about cells is true? A. all cells are alike in structure B.cells in a tissue perform different functions C. in a multicellular organism, each cell is independent. D. a part of a cell is called an organ . E. a cell can exist as an independent organism.
5a. Describe the structure of a plant cell.
b.state three similarities between plant and animal cells.
c.state three differences between plant and animal cells.
6.Describe the functions of the following.
a.the cell membrane b. the nucleus c. the mitochondrion d.the Golgi bodies in cell.
FORMS IN WHICH LIVING CELL EXIST
Cell of different organisms exist in different forms. Some are single and free living, others may be colonial, filamentous or part of a living organisms
Cell as independent or single or free living organisms. Cell may live as independent organisms capable of living freely on their own. Such organism even though it has only one cell is able to carry out life processes such as Movement, Reproductions, Sensitivity, Excretion, Growth e.t.c. Example of such organisms are Amoeba, Paramecium, Euglena, Chlamydomonas.
The Chlamydomonas is oral or spherical in shape and is bounded by cell wall consisting of hemi-cellulose. At the anterior end, the wall projects and thickens into a colourless papilla. Two flagella which arise from the anterior end are used fo rmovement. Chose to the base of the flagella are two contractile vacuoles which are used for osmoregulation.
Within the cytoplasm is the nucleus and a cup shaped chloroplast which contains chlorophyll which the organism use for A pyrenoid responsible for the storage of starch occur within the chloroplast. An eye spot is embedded on one side of the cell close to the anterior end. The eye spot responds to light stimulus. Chlamydomonas is an organism that shares both the characteristics of plants and animals. The animal characteristics include flagella for locomotion, eye sport responds to light source, contractile vacuole for osmoregulation. The presence of chloroplast containing chlorophyll for photosynthesis and storage excess carbohydrate as starch are plant characteristic chlamydomonas
The organism is a single celled, naked colourless, microscopic about 0.07mm, shapeless and jelly-like animal. It is made up of cytoplasm and nucleus. The nucleus is divided into non-gramular liquid layer called ectoplasm and granular layer called endoplasm. The cytoplasm is bounded by a thin flexible cell membrane called plasma membrane which keep the cell content or plasmalema together. The ectoplasm forms pseudopodia (false feet) for movement and capturing of food. Exchange of gases (oxygen and carbon iv oxide) and ammonia occurs at the ectoplasm. The endoplasm is divided into an outer viscous portion called plasmagel and an inner liquid portion called plasmasol. The plasmasol contain the following cytoplasmic structured.
Contractile Vacuole: It excretes liquid product such as dissolved ammonia and regulates amount of water and mineral salt that enter and leave the cell (osmoregulation).
Food Vacuole: It is used for storage and digestion of food
Nucleus contains chromosome which are hereditary unit.
The organism is slipper shaped with a length ranging 0.15 to 0.30mm. the anterior part is blunt or rounder while the posterior part is pointed. Paramecium Caudatum is divided into two distinct parts, the ectoplasm and the endoplasm. The thin layer of ectoplasm is bounded outside by a clear and elastic membrane called pellicle which make the animal having a definite slipper shape. The entire pellicle is covered fine cilia used for locomotion, embedded in the ectoplasm are spindle shaped bodies called trichoicyst which contains filaments that can be discharged either to trap a prey and hold it or used for offense and defence.
The endoplasm is granular, large and contains the following organells anterior and posterior contractile vacuoles, food vacuoles which are formed near the gullet (cytopharynx. There are two nuclear- meganucleus and micronucleus which are centrally phased in the endoplasm. The maganucleus is bean shaped or kidney shaped. It controls the ordinary activities of the cell.
The two contractile vacuoles are used to remove excess water from the animal.
At one side of P. caudatum is a depression called oral groove which lead to a gullet through which food particle can be swallowed. At the posterior and is a small opening anal pore through which indigested food material is ejected from the body.
Euglena is a pear or spindle shaped single celled organism. It is about 0.66mm in length with the widest width at the middle of the body. The anterior part is blunt or rounded while the posterior part is pointed. The body is divided into clear ectoplasm and granular endoplasm. The organism lives in water. It is a boarder line between plant and animal
The ectoplasm (plasmagel) is bonded by a thin, flexible, tough and elastic covering called pellicle which enable the animal to carry out a type of locomotion called euglenoid movement. Within the cytoplasm are rod-shaped structures called chloroplast which contain chlorophyll hence Euglena is green in colour and is able to carry out photosynthesis.
The granular endoplasm (plasmasol) contains myonemes ( thin fibres) and paramylum granules containing starch reserve. The nucleus is bounded by a nuclear membrane which contain the nucleolus and nucleolus. At the anterior part of the organism is a flask-shaped opening called gullet. Below the gullet is a granule called blepharoblast. Arising from the blapharoblast a rhizoplast arising the blepharoblast is rhizoplast believe to initiate cell division. From the flagellum used for locomotion, at the base of the gullet lies a large contractile vacuole used for osmoregulation. There is presence of eye spot which respond to light stimulus
Euglena has a mixture of plant food and animal characteristics
Euglena as a plant
(i)The presence of chloroplast which is used for photosynthesis
(ii)Stores excess carbohydrate as starch called paramylum granules only plant stores starch
(iii)Definite shape (pellicle)
Euglena as an animal
(i)Possession of eye spot which sensitive to light. It is not used for sight
(ii)Possession of flagellum for locomotion
(iii)It carries out holozoic feeding in the absence of sun light by using the gullet to ingest foodparticles
(iv)Contractile vacuole for osmoregulation
(v)No cellulose cell wall but flexible living pellicle
(vi)No central cell sap vacuole is small and not central
Cell as a colony
Certain organism are composed or numerous and similar cells joined by strand of protoplasm. Each associating cell has nucleus,cytoplasm and a pair of flagella. The flagella enable the colony to swim by rolling over and over. The cells making up the colony are not differentiated into tissues e.g. Eudorina pandorina and volvox
Cell as a filament
Some independent cells arranged themselves into filament. The filament of spirogyra consists of
about twelve cylindrical cells all similar in size bound together by a cell wall and mucilage, each cell is separated from the other by intercellular cell walls. Each cell can live independently and is capable of carrying out asexual reproduction to form a new filament.
Spirogyra is an unbranched green filamentous alga consisting of a chain of cylindrical cells. The entire filament is covered with a layer of mucilage which makes it slimy. Inside each cell is a lining central vacuole. In the cytoplasm the chloroplasts are arranged spirally. Each chloroplast contains pyrenoids. The nucleus is suspended by cytoplasmic threads.
Cell as part of a living organisms
Most multicellular organisms are made up of groups of cells which are similar in shape and structure. The cell making in shape and structure. The cells making up the group work together for a particular function. The specialized group of cells is called tissue. Each cell depends on the other for efficient performance.
(a)What is a cell?
(b)Outline the cell theory as propounded by the following biologist
Robert Hook, Dujardin, Schleiden Mathias and Theordor Schwann
(c)Make a diagram 8 10 cm long of chlamydomonas and label the diagram full
(d)State (i) two advantages and
(ii) Two disadvantages of a unicellular organisms has over a multicellular organisms
THE CELL AND ITS ENVIRONMENT
DIFFUSION: is the process by which molecules of substances, such as liquid gases move randomly from a region of higher concentration to a region of lower concentration until the particles are evenly distributed. Diffusion can occur in air, liquid and solid.
Biological significance: It is a process by which fine particles or molecules flow in and ;out of cells living things and it can occur in non-living material. By diffusion molecules of substance evenly spread in any available space.
Factors Affecting rate of diffusion
(i)State of matter of diffusing molecules
(ii)Molecular size of the diffusing molecules
(iii)Differences in concentration of diffusing molecules and the medium
(iv)Temperature: High temperature increases the speed at which molecules move thus, the higher the temperature, the faster the rate of diffusion.
Demonstration Diffusion in Liquid
Fill a beaker with distilled water use pipette to deliver small quantity of potassium permanganate solution gently at the bottom of the beaker and leave it to stand for few minutes. The purple colour of the potassium permanganate solution starts to spread outside.
Gradually, the colour spreads evenly throughout the water medium so that the water have the same shade of purple colour.
Demonstration of Diffusion in Gases
Take a bottle of ammonia solution, open the bottle and move some distance away from the bottle and wait for some time. The smell of the ammonia gas shows that diffusion of ammonia gas has taken place.
Importance of Diffusion in Plant
(i)Diffusion acids movement of oxygen produced during photosynthesis into the atmosphere
(ii)Diffusion assists easy movement of carbon (iv) oxide from the atmosphere into the leaves through the stomata cell
(iii)Diffusion promotes free movement of oxygen needed for respiration from the atmosphere into the plant through stomata cell
(iv)Movement of water vapour from the leaves of plant to outside in a process called transpiration is possible because of diffusion
Importance of diffusion in Animal
(i)Absorption of glucose and other food material through the villi in the small intestine in through diffusion
(ii)Diffusion aids the exchange of body nutrients in the placenta from the mother to a developing foetus
(iii)Diffusion aids gaseous exchange in many cells and organisms for instance amoeba takes in oxygen and get rid of carbon (iv) oxide by diffusion
(iv)Diffusion aids the movement of carbon (iv) oxide form the lungs capillaries into the air sac and vice- versa.
Osmosis is defined as the movement of water molecules from a region of low concentration fo solute to a region of high concentration of solute through a semi-permeable membrane separating the two solution until equilibrium is attained.
A solution with higher solute concentration has a smaller amount of water left for dissolution of more solute, while a solution with lower concentration of solute has more water available.
Condition necessary for osmosis to take place
(i)Presence of a stronger solution e.g. sugar or salt solution
(ii)Presence of weaker solution e.g. distilled water
(iii)Presence of a selective or differentially permeable membrane/pig bladder
Types of solution
(i)Hypertonic Solution is a solution which gains water in osmosis or that is higher in concentration
(ii)Hypotonic Solution is a solution that lose water in osmosis or a solution that is weak-distilled water
(iii)Isotonic solution: when a state of equillibrum is established between two solution, that is neither solutions gains or loses water.
Osmosis is a special form of diffusion
- Diffusion occurs in gases and liquid Osmosis occur in liquid medium only
- Differently permeable membrane is not Differentially permeable membrane is required required
- It occurs in living and non-living organisms It occurs naturally in living organisms
- Molecules diffuse into any space accessible Water molecules move between two solutions
to them of different osmotic pressure leading to the
Establishment of an osmotic equilibrium
Demonstration of Osmosis using living cell
Aim:– To demonstrate the process of osmosis using a living tissue e.g. Yam or Pawpaw
Method: Two thick slices of yam A and B are obtained and their skin peeled off. A large cavity is drilled into the middle of each. A strong solution of salt is poured into A. Yam slice B is left without salt to serve as a control. They are both kept in a trough containing distilled water and allowed to stand for some hours.
Result: After some time, it is observed that the water level in yam slice A rises tremendously while no water rise is observed in B. Water molecules moved from the rough yam slice A
Conclusion: It can be concluded that living tissue have semi-permeable membrane which allows molecules to pass through from the surrounding if they have higher osmotic pressure. Water could not move to Yam slice B since it contained no salt or sugar solution. It is therefore of the same osmotic pressure with the water in the trough
Experiment to demonstrate osmosis using a non-living material
Aim: To demonstrate osmosis using non-living material
Method: A piece of cellophane packet is tied over the mouth of a thistle funnel carefully and tightly. The cup of the thistle funnel is filled with sugar solution while the beaker contains water.
The cup side carrying the semi-permeable membrane is immersed into the beaker of water, the experiment is left for one day. The control experiment is similarly arranged but instead of filling the funnel with sugar solution it is filled with water.
Result: After few hours the level of liquid in the funnel has risen to its original marks. There is no rise in the control experiment.
Conclusion: Water has passed through the semi-permeable membrane to the sugar solution by osmosis (endosmosis)
Biological Significance of Osmosis
Osmosis is a special form of diffusion. Diffusion allows free movement of substances without hindrance, but osmosis because of the selective permeable membrane allow some particles to pass through them while other cannot. All living cells have cell membranes which are selective to control or select which substances of outer or leave the cell.
Plasmolysis is defined as the shrinkage of the cytoplasmic lining from the cell wall or cell membrane when the cell is placed in a more concentrated solution. This can be observed when plant cell is placed in a more concentrated salt or sugar solution than that of the cell sap, water is lost by exosmosis. As a result of water loss the cell become flaccid.
When the plasmolysed cell is again placed in distilled water (hypotonic solution), water moves into the cell sap solution is in the vacuole increases in volume and distend towards the cytoplasm and cell wall. The shrinkage or red blood cell is crenation
Haemolysis is defined as inward movement of water uncontrollably into a cell when the cell is surrounded by hypotonic solution to the port of bursting in a process called endosmosis.
Haemolysis is the process by which red blood cells become split or burst as a result of excessive intake of water called endosmosis.
Normally, the blood and red blood compuseles are isotonic, that is bod red blood cell and the plasma have the same osmotic concentration. Mammalian plasma and red blood cell have sodium chloride solution.
If for some reason, the concentration of salt in the plasma falls i.e become hypotonic water will enter the red blood cells by osmosis called endosmosis through the cell membrane continuous absorption of water into the cell will make the cells very turgid and eventually burst haemolysis will lead to anaemia which may cause death.
Condition that cause haemolysis
(ii) abuse of use of drugs
(iii)Food poisoning, infection/epidermics industrial activities/pollution
TURGIDITY: is defined as the condition in which cells absorb plenty of water up to a point where the cell is fully stretched. At this point, the cell is said to be turgid. Turgidity occurs when a cell is place in hypotonic solution. Turgidity is useful to plant because it make them stand erect, give support, make them stand erect, give support to the stem, leaves, flower and guard cells
FLACCIDITY: is defined as the condition in which plants lose water to their surroundings faster than they can absorb. When plants lose more water, it is said to be flaccid. Flaccidity normal occur when there is no water in the soil during drought. The situation may cause plant to wilt or even die if last for a very long time
1i.Explain what happens to a red blood cell when placed in a hypotonic solution
ii.Mention three conditions that may cause haemolysis
b.Describe an experiment to show the effect of plasmolysis on a fresh filament of spirogyra
ii.How can the process be reversed
c(i).Describe an experiment to demonstrate osmosis using a living material
ii.Give two differences between osmosis and diffusion
d.A normal plants was watered daily with a hypertonic solution for about seven (7) days.
Itwasdiscovered that the plant was not doing well. Explain why.
(b) Explain why red blood cells swell and later burst when placed in a distilled water
(c) State four important of diffusion to animal
3a. Describe one experiment, using a non-living material to demonstrate osmosis
(b). Use the result of your experiment to explain how water passes from the soil into the root hair of a plant, through what cell does if then pass on its way to the stem
4.The diffusion rates of gases are generally higher than those of liquids because
- atmospheric air is much lighter than water B.gas molecules move faster than those of liquids.
C.the proportion of the atmosphere which is gaseous is very high..D.liquids tend to cool down
more quicklythan gases do.E. none of the above.
5.Haemolysis is an example of A. osmosis B. plasmolysis C.active transport D.hydrolysis E.
6The toad does not normally drink water, but when placed in a dish of salt water, however, a toad
may drink water. This is because the toad A.is absorbing molecules of salt through the skin B.is
losing salt too rapidly to its salty enviroment.C. requires salt from its surroundings for its bone
formation D. is losing water from its body to its salty surroundings E.requires water from its
surroundings for a balanced diet as an amphibian.
SOME PROPERTIES AND FUNCTION OF THE CELL
Nutrition is defined as the process by which living organisms obtain and utilize food materials from external environment for metabolic activities such as respiration, growth, excretion and reproduction.
Food is any substance which when absorbed into the body cells yields energy and materials for growth, repairs of damaged tissues and regulation of body processes without harming the living organism.
Anabolism is defined as the synthesis of complex organic compound from simple substances. Living things require food( carbohydrtate, protein, lipids,mineral salt ,vitamins and water) for the following activities
- production of new protoplasm
iii.Repair of body cells and tissues.
iv.production of energy for life activities.
Types of Nutrition
1.Autotrophic Nutrition is the type of nutrition in which organisms are able to manufacture their own food. organism which can manufacture or synthesize their own food are called autotrophs. Autotrophic mode of nutrition is carried out by green plants through the process of photosynthesis and some certain bacteria through the process of chemosynthesis..
Photosynthetic (Holophytic) Nutrition is the process where green plants manufacture their own
organic food from simple inorganic substances such as carbondioxide, water, sunlight and chlorophyll with the release of oxygen as by-product.
6CO2+6H20 Sunlight energy C6H12O6+6CO2
Chemosynthetic Nutrition: is a process where certain bacteria which are autotrophic manufacture their own food through simple inorganic substances such as carbon (iv) oxide, water, hydrogen sulsphide by using the chemical energy released during the process as source of energy.
These bacteria do not depend upon sunlight energy. They have enzyme system capable of trapping chemical energy. For example, the sulphur bacteria in the soil can oxidize hydrogen around it to chemical energy
2H2S+O2 S+2H20 + Chemical Energy
Heterotrophic Nutrition is a type of nutrition in which organisms cannot manufacture their own food but depends directly on plants for their own food. Such organisms are called heterotrophs. Most heterotrophs are fungi, protozoa and some bacteria. Heterotrophs take food items into their gut in three different forms
1.Macrophagous feeder are animal such as mammals that take large food item which need the aid of teeth to break down before entering digestive gut
2.Microphagous feeders are other heterotrophs which take tiny food particles into their gut without being broken down by teeth. Examples are paramecium, mosquito larvae and tilapia galilaea
3.Some other heterotrophs feed on fluid and they are referred to as fluid feeders. Examples are adult mosquitoes, aphids, butter flies and sunbird.
There are four main types of heterotrophs nutrition
Plants require mineral nutrients or elements obtained from the soil in form of solution for good growth and healthy development. The source is the main source of mineral salts while gaseous elements such as oxygen, hydrogen and carbon are mainly derived from the atmosphere. These plants nutrients elements are grouped into two classes depending on the quantity required by the plants
(1)Macro nutrients or elements are mineral elements required in large quantities for healthy growth of plants. Example are nitrogen, phosphorus, potassium, magnesium, calcium, oxygen, hydrogen, carbon, sulphur and iron. These macro element are called essential element.
(2)Micro nutrients or elements or traced element are those mineral elements required in small quantities for healthy growth of plants. Examples are zinc, copper, boron, molybdenum, colbat, chlorine and manganese. When a plant lacks any of these elements, it shows certain signs and these signs are called deficiency symptoms. The micro nutrients are also called non-essential element.
Cellular respiration is defined as the oxidation of organic food substance in the cells particularly in the mitochondrion to release energy inform of ATPS (Adenosine Triphophate) All living organisms require energy to do work. Energy is abound in food molecules. The energy in the food molecules is called potential energy. This potential energy can only be used for work energy is abound in food molecules. The energy in the food molecules is called potential energy. This potential energy can only be used for work when it has been converted into kinetic energy.
CHEMEICAL PROCESSES OF CELLULAR RESPIRATION
Cellular respiration occurs in two aim stages involving series of chemical reactions and respiratory enzymes.
First stages Glycolysis
Glycolysis is a series of chemical reaction which involves the breaking down of glucoses to a 3-carbon molecule of pyruvic acid.
In this process, the glucose molecules is phosphorylated by addition of phosphate group to glucose to become glucose phosphate through series of oxidative enzymes, the glucose phosphate is converted to two molecules of triose sugar (a 3-carbon sugar). The triose sugar is converted to pyruvic acid by removal of four atoms of hydrogen by co-enzymes called NAD (Nicotinamide adenine dinueleotide) with the formation of 2ATP.
C6H12O6 Glycolysis 2C3H4O3+2H2+2ATP
Second Stage: Aerobic Respiration
This stage occurs in the mitochondrion if sufficient oxygen is available, each molecule of pyruvic is oxidized to remove one molecule of carbon (iv) oxide (decarboxylation) and two atoms of hydrogen (dehydrogenation) forming one molecule of acetic acid a 2-carbon acid or acety co-enzymes.
A.Carbon (iv) oxide is released. Kreb cycle or citric acid cycle. The acetic acid entries into a kreb cycle where it is joined to a 4-carbon acid oxaloacetic acid present in the mitochondria to form citric acid a 6-carbon acid
One molecule of carbon (iv) oxide and one atom of hydrogen are removed by oxidative decarboxylation and NAD respectively to form a 5-carbon acid ketoghitaric acid. Another molecule of carbon (iv) oxide and one atom of hydrogen are further removed from ketogluteric acid to form a 4-carbon succinic acid. One atom of hydrogen is removed from succinic acid to form a 4-carbon malic acid. Again another hydrogen atom is removed from malic acid to form a 4-carbon oxaloacotic acid. The oxaloacetic aid then combines with acetic acid again and the cycle is repeated. The hydrogen atoms removed in succeeding stages combine with molecular oxygen to form water. The overall reactions of glycolysis and kreb’s cycle is represented by an equation.
C6H12O6+602 6CO2+6H20 + ENERGY (38ATP)
ATP is a water soluble energy carrying small molecules that is transported around cells.
The process of glycolysis is a catabolic process because it involves breaking down of complex organic molecule glucose to simple moleculses such as ATP. ### process realeses energy. In glycolysis one molecule of glucose releases 2ATP of energy. In kreb cycle 1 molecule of glucose releases 38ATP of energy.
This is the type of respiration which requires oxygen to break down glucose into water, carbondioxide and energy (ATP). This type of respiration is commonly carried out by most living thing
Anaerobic Respiration is the type of respiration in which the glucose is broken down inside the cell without oxygen to produce carbon (iv) oxide and ethanol and 2ATP.
(a)Alcoholic Fermentation is the type of respiration in which glucose is first converted to pyruvic acid. The pyruvic acid is then reduced to ethanol by accepting the hydrogen of NADH. This type of respiration on is common to some organism that respire anaerobically such as yeast, bacteria, fungi and endoparasite such as tape worm and round warm
C6H12O6 No 2CO2 +2C2H5OH+ Energy
Glucose O2 Carbon(iv) oxide (Alcohol) 2ATPS
(b)Lactic acid fermentation is the type of anaerobic respiration where glucose is broken down to
pyruvic aid. The pyruvic acid is then reduced to lactic acid by NADH without the production of
carbon (iv) oxide.
Lactic acid fermentation often occurs in the muscles of animal after a very fast race or strenuous exercise. In the absence of oxygen reaching the muscle cells, the pyruvic acid reduce to lactic acid whose accumulation in the muscle ells causes temporary muscle fatigue and aches. The athlete recovers when sufficient oxygen is carried to the muscle cell. Which oxidize the lactic acid to pyruvic acid and pyruvic acid is oxidized by the supplied oxygen to give carbon (iv) oxide, water and energy. The muscle cell then recovers
2CH3COCOOH CH3CHOHCOOH + 2NAD+ 2ATP
Pyruvic acid Lactic acid
Differences Between Aerobic and Anaerobic Respiration
- Occurs in most animals as well as occurs in some bacteria, fungi and cells of the muscles of
Plant cells animals
- Oxygen is needed oxygen is not needed
- Produce greater energy (38ATP) per Produce lesser energy 2ATPs per molecule of glucose
Molecule of glucose
- Carbon (iv) oxide and water are the Carbon (iv) oxide and alcohole or lactic acid are the by-
- It takes place in mitochondria it takes place in the cypoplasm
- Explain briefly the term muscle fatique
- Name the structure in a cell in which ATP is formed
– Define the term internal respiration
2a. What is the importance of ATP
– Briefly describe the simplified chemical process of cellular respiration
– In a tabular form state the difference between aerobic and anaerobic respiration
– Write chemical equation only to explain
(i) Aerobic respiration
(ii) Anaerobic respiration
- Define fermentation
– Lactic fermentation
– Alcoholic fermentation
Growth is defined as an irreversible increase in volume, size, numbering of parts, length and weight of an organism. It is an organic process which takes some time to accomplish. Growth however occur faster in young organisms than older ones.
The three processes involve in growth
(i)Cell division is a process by which cell increases in number and is achieved by cell division called mitosis. The division of cell commences with synthesis of new protoplasm leading to the doubling of the chromosomes number in a process called replication before cell actually divide into two, with each daughter cell having the same chromosome as parent cell.
There are two types of cell division
(i)Mitosis which is a cell division that lead to growth
(ii)Meiosis is a cell division that lead to formation of gametes
This is a process which follows cell division. After mitotic division in animals, the daughter cells absorb nutrients from their surrounding which it uses to increase in mass and size. Part of the nutrient is used for respiration to generate energy while the remaining is assimilated resulting in the enlargement of the cells.
This process takes place after cell enlargement in which each cell develops into a special type of cell by changing its shape and structure in order to carry out a specialized or particular function. Cell differentiation is important in the growth and development of a mature multi cellular organisms.
Mitosis is a division of cell which produces two identical cells with the same number of chromosomes and characteristics as those of the parent cell. Mitosis is a cell division that lead to growth and it occurs in somatic cell(body cells) such as skin, bone marrow, lymph nodes and injured places and meristimatic tissues of plant. Mitosis occurs in five stages namely interphase, prophase, metaphase, anaphase and telephase.
- Interphase- This is a resting stage of the cell: At this stage, the cell has normal appearance of non-dividing cell condition. chromosomes are not clearly visible.
- Prophase- The chromosomes become visible as chromatin threads. The chromosomes become shorter, thicker and clearly visible. Each chromosome now forms two district chromatrids joined by a centrometre.
Nucleolus is gradually disappearing and formation of spindle fibres commence.
- Metaphase- At metaphase the chromosomes (now parried) called chromatids arranged themselves along the equator or middle of the spindle. The chromatids are attached to the spindle by centrometre.
- Anaphase- The chromatids of each chromosome separate. The start migrating to the poles of the cell by elongation of the spindle axis. The chromatids eventually reach the pole.
- Telophase (cytokinesis)- The cell starts dividing into two by line of division at the equator. The chromosome looses their thick appearance and the nuclear material, nucleus and nuclear membrane reformed. The spindle structure disappear and the cell split completely into two daughter cells having the same condition as interphase. The
- division of the cell at telophase into daughter cells is called cytokinesis
Apical and Intercalary Growth
Growth does not occur any how in all parts of the plant. It takes place in certain tissue and places in a plant bodies. The tissue where growth takes place plant is called meristem or MERISTIMATIC TISSUE.
A meristem is a tissue that retain their ability to divide by mitosis and turn out new cells. Such meristimatic tissues include root apex, stem or shoot apex base or internodes and vascular cambium.
Growth which occur in the apical stem and root meristem is called apical growth while growth which occurs at meristem base of internodes is called auxiliary growth
Hormones or chemical or biochemical substances produced in small quantity by cell of the body of plant and animal that have profound effect on other part of their body where they are needed for some form of growth
Plant hormones are produced only at the growing parts such as apical meristem of shoot or root i.e. shoot tip or root tip and transported to other part by diffusion.
Example of plant hormones are auxin, gibberellin, cytokinin, abscissic acid and florigens. Plant hormones help plant in the following ways.
- It promotes stem enlongation
- It makes plant to respond to tropism
iii. It causes root and stem apical division
- It causes fruit growth and ripening
- It causes flower bud and lateral root initiation
In animal, hormones are produced inductless glands called endocrine system and release straight to the blood stream which transport them to the target organ. Animal hormones include the following
GLANDS SITE HORMONE
- Pituitary gland base of head Pituitrin
- Thyroid gland Neck Thyroxine
- Parathyroid Neck Parathormone
- Pancreas Loop of duodenum Insulin
- Adrenal gland Top of each kidney Adrenaline
- Testes Testes Testosterone
- Ovaries Ovaries Progesterone
FUNCTION OF ANIMAL HORMONE
- It controls body metabolism
- It promotes growth of the animal
iii. It induces or stimulates reproduction
Growth is quantative and measurable, so that the amount of growth achieved by plant can be expereseed. The measures for growth in plant include
- increase in the height or length of the stem, root and any other organ of the plant
- Increase in the girth or width or circumference of the stem
iii. Increase in the area of leaves
- Increase in weight
- Increase in the number of branches
- In animal measurement in growth in length of animal
The rate of growth of a plant is usually studied by measuring the rate of increase in length or height of the shoot or root of the plant. Rate of growth varies with age of the plant. A young seedling is a good choice. The amount of growth achieved by a seedling of 24hrs interval over a known period of time represent the rate of growth.
The increase in height (mm) can be plotted on a graph over a time intervals. The rate of enlongation or height growth is seen to vary from individual to individual and from species to species. The graghs are the same.
In all cases, the rate of growth is at first slow, then rises up to a part and continuous at this rapid rate until maturity and later declines. The graphs shows a typical s-shaped curve called sigmoid growth curve. The sigmoid growth curve is characteristic of all living organisms. It is the typical growth curve for the whole plant as well as for its individual organs.
1a. Define the term growth as applied to living things
- State three similarities and three differences between the growth in plants and animals
- List four factors that affect the growth of living organisms
- What role does mitosis play in growth?
Irritability is the ability of an organism to perceive and respond to changes in internal and external environment or stimuli. Stimulus is a change in condition which produces a change in the activities of the organism or part of its body. A stimulus can either be external or internal. External stimuli are those environmental factor that evoke response. Organisms respond to stimulus in three ways namely tactic, nastic and trophic response.
Tactic Response or taxis is a directional type of response or movement in which the whole organism moves from one place to another in response to external stimulus such as light, temperature, water or certain chemical. The response is thus said to directional and positive if the organism moves towards the stimulus or it is negative if it moves away from the stimulus.
– Photo taxis is the response to variation in light intensity
– Chemo taxis is the response to variation in concentration of chemical substance
– Aero taxis is the response to variation in concentration of oxygen
– Osmotaxis is the response to variation in osmotic condition
– Rheotaxis is the response to variation in the direction of the flow of liquid e.g.
Nastic Response or Nastism: This is a type of response in which a part of a plant moves in response to non-directional stimulus such as changes in light intensity, temperature and humidity.
Nastic movements are varied in nature and may be as a result of growth curvature or of sudden changes in tugor.
Nastic responses are usually described according to the stimulus evoking them.
(i) Nyctinasty is a response to changing in day and night condition (temperature) or light e.g.
– The opening of the petals of sun flower in the light and closes in the dark
– The closing of the morning glory flower when light intensity is low
(ii)Haptonasty is the response due to contact or touch
– The infolding of the leaflet of mimosa plant when touched.
– The closing of leaflet of flamboyant tree.
– The nastic movement of floral parts during pollination mechanism and movement of leaves of insectivorous plant
(iii) Hydronasty is the response to humidity changes
(iv) Chemonasty is the response to the presence of chemical
Tropic response or tropism: This is a type of response in which a part of a plant moves in response to directional stimulus.
Tropism are growth movement named according to the stimulus e.g. phototropism, hydrotropism, chemotropism, haptotropism or thigmotropism, geotropism.
Phototropism is the growth movement in response to light, thus the direction of growth movement depends on the direction of light. The shoot of plant is positively phototropic.
Aim: To show that shoots are positively prototrophic
Material Required: Two boxes, seedling growing in pot, kmife, aluminium foil
Procedure: The two boxes are arranged in a proper way. Some afermenting bean seeds are placed in two boxes with a hole cut at one end. Box A contains normal seedlings while B contains seedlings with a caps of aluminium. The inside of each box is painted black to prevent light reflection. The entire experiment is put on the window and observed for few days
Observation: The shoot of the seedling in box A will be observed to bend towards the source of light while those in box B do not
Conclusion: Since the shoot of seedlings bend toward light, it shows that the shoot is positively phototrophic
Geotropism: This is a response to gravitational force. The shoot of plant is negatively geotropic while the root is positively geotropic.
Aim: To show that plants root respond positively to gravity
Material Required: Bean seedlings, pins and klinostat
Procedure: Select six similar seedlings with straight radicles and plumules. Pin three seedlings to the turnable of a klinostat so that they are horizontal. In the real experiment, do not let turable rotate so that it can receive the stimulus of gravity from one direction. Pin the remaining three seedlings to another klinostat in an identical ways, but allow the turnable to rotate slowly so that the seedlings receive the stimulus of gravity equally on all sides (to serve as control experiment)
Observation: in the stationary seedlings, the plumules will bend and grow vertically upward while the radicles will bend and grow vertically downward. But the seedlings in the rotating klinostat will continue to grow horizontally
Result: The plumule have responded to one-sided gravity by growing away from it i.e. they are negatively geotropic. The radicles (root) however responded by growing towards the direction of the stimulus i.e. they are positively geotropic
Conclusion: This shows that the roots of plant are positively geotropic
Hydrotropism: This is the response to water source. Roots of plants will always grow towards a water source
Chemotropism is the response of plant to concentration of chemical substance e.g. roots respond positively to the presence of salt, particularly salt of calcium but negatively to alkaline or acid concentration.
Haptrotropism /(Thigmotropism) is a response of plant to contact and is characteristic of tendrils and other organs by which the plant secures support. Tendrils show positive response to touch by twinkling around a support while roots on the other hand show a negative response to touch by growing away from stones.
Traumotropism: is a response to wounding. Some roots show curvature as a result of damage on one side, the curvature always being away from the injured side.
Thermotropism: is a response to heat
Rheotropism is a response to water current
Movement is the ability of living organisms to move from one place to another.
Reasons for Movement
- To search for food
ii To escape from danger
iii. To respond to stimulus either positively or negatively
- For the sake of reproduction
The cytoplasm as a whole of normally in motion. Irregular streaming often occurs but at other times, the contents of the cell are subjected contents of the cell are subjected to cynical currents moving constantly in one direction. This is known as cyclosis. The cellular organelles are swept along passively by these streams or current.
Organisms Organelles for movement Mechanism of movement
Amoeba Pseudopodia Cytoplasmic streaming (cyclosis)
Paramecium Cilia Beating the cilia against water
Euglena Flagellum Lashing movement of flagellum
Hydra Tentacles Swimming, swaying, hoping and
Earthworm Chaetae Crawling
Fishes Fins Swimming
Toads and frog Limbs Hopping
1a. What is meant by term tropism?
- How do plants response to the external stimulus of light
- explain what is meant nastic response
Reproduction is the ability of living organisms to produce new individual of their type or new offspring. Reproduction is necessary for increase in number and perpetuation of life. Reproduction is divided into two types
1.ASEXUAL REPRODUTION: is a type of reproduction which only one part is involved to produce offspring by itself without formation and fussion of granuder offsprings which are identical (clones) to the parent cells are always produced
Types of Asexual Reproductioni.Binary Fission: this is the simplest form of asexual reproduction during which a parent organisms, divided into two parts or more than two equal parts. The mucus first divides into two parts. The nucleus part divides into two parts. Then follows the division of the cytoplasm. After the completion of the division of the cytoplasm, two daughter cell are formed. Example can be seen in Amoeba, Paramecium or Euglena
ii.Budding: the new offspring formed developed as a protusion or outgrowth of the parent. This outgrowth is referred to a BUD. The bud may form on an internal or external buds break off from the independent life. Examples are yeast, hydra, coral and polyps.
iii.Spore Formation: certain plants such as fungi reproduce asexually by spores which are small unicellular bodies. They are light and can be easily be dispersed by air. Each spore can develop to an independent organisms. This independent organism develops a hypha which grows from the substrate to the air. These are termed aerial hyphae or sporangiophores. The tip of these aeria hyphae become swollen to form sporangia which houses the spores.
Fragmentation: an organism may break into two or more pieces and each piece can then develop into a new individual organism. Examples are spirogyra, sponges and coelenterates.
Vegetative propagation involves the use of parts of plants in multiplying the plant or when a new plant grows out of a parent plant, without the use of seeds. Vegetative propagation involves two methods.
(i)Natural vegetative propagation: is carried out by plant themselves by means of leaves, stems and buds.
– leaves: tiny plants grow from the leaf which later break off to form a new plant. Bryophyllum and Begonia are good examples. In Bryophyllum and Begonia are good examples. In Bryophyllum the tiny plants grow from the veins at the end of the leaf margin while Begonia, they grow form the veins on the surface leaf.
– Stem: stems of different plants have modified themselves in different ways to carry out vegetative propagation. Some stems are modified as runners, rhizomes, corms and tubers.
– Runners: stem runners such as sweet potatoes grow horizontally along the ground
– Rhizomes: A rhizomes is a thick fleshy underground stem which grows more or less horizontally below the surface of the soil. Food is stored in the stem as starch. It has nodes and internodes. The scale leaves are membraneous and cover lateral bud at the modes e.g. canna lily and ginger.
– Corms: This is an underground stem which grows vertically in the soil. The stem is short and swollen with food reserve. Scale leaves, nodes, lateral buds are arranged over it while terminal bud is at the top. The new corm has adventitious and contractile roofs.
-Stem tuber: stem tubers have the terminal ends of their underground stems swollen with food reserve plants like yams and sweet potatoes which develop tubers. The underground stem tuber is left below in the non-growing season. The dormant underground tuber gives rise to another aerial shoot when rain return in the next growing season.
Sweet potato, the tuber has auxiliary buds covered with sale leaves.
– Suckers: suckers are underground young plants which develop from the axilliary buds of the parent plants. The terminal buds of suckers grow above the soil to form shoot. Examples of plants that develop suckers of the base of their stems are plantain, banana and pineapple.
(i) Bulb: The shoot of some plants are modified to form underground buds for vegetative propagation. Example of bulb is onion, tulip and daffodil. Bulbs are underground compressed shoot or buds. The stem is very short with inner scale leaves which are fleshy and swollen with food reserves. They overlay and the out leaves are by dry, scaly and brownish terminal and lateral buds are parent. Adventitious root rise from the short stem.
(ii)Artificial vegetative propagation: this is carried out by planting parts of perennating organs (organs that survive from one growing season to the next) like tubers and rhizomes. Each perennating part must possess a bud which can develop into a new plant
i.Budding: This is the bring together of the bud and stock. The bud and stock. The bud is taken from a tree already producing or matured. This forms the bud stock or slip the stock is a young plant of about a year old. During building, a T-shaped cut or inverted T in made at about 45cm from the ground on the stem of the stock plant. The cut shape is slight by raised to expose the cambium. The bud is carefully slipped into the raised bark and pressed formly to ensure that the cambia of both bud and stock unite together. It is commonly used in citrus to select desired species.
- Layering: this involves bending shoot or branch of a plant to the ground so that the nodes can make contact with the soil. It is then pegged below the ground and covered with rich soil to provide good medium root development. When roots have emerged the branch is cut form the parent plant-layering can be used in coffee, cocoa and kola production
iii.Cutting: this involves the use of mature stem or branch to propagate plants. This is a very common method of asexual propagation in many crops such as cassava, croton and sugar-cane. The plant produced have the same character as the original plant from the cuttings were obtained. The cutting should be about 20cm long or convenient length with two or three nodes or buds. It should be put into ground to enable it have contact with the soil. It should be watered after planting or raised in shade during dry season or planted during the rain.
iv.Grafting: this is the union of the stock and scion. The part of the plant whose root is in the ground is called the stock while the shoot removed from other plant is called scion. The two plants must be of the same species or closely related species. The plant should be of the same age and size for grafting to be possible. Both plants are cut in a slant or V-shape to provide good surfaces fro contact. They are then tied together with plastic tape or any device to keep them in place the junction is rubbed with grafting wax to prevent the entrance of air, water and pathogens
- Marcotting: This is a practical vegetative propagation method in which the back of a branch
is peeled off with a knife, up to a considerable length (5cm). Soil rich in organic nature is tied to the pealed portion by means of coconut husk or any suitable device. It is watered to keep it moist always.
After a time, roots will grow out of the peeled portion. As the roofs become strong enough, the branch is cut off the plant. The roofed branch is planted into the soil to give rise to a new plant. The method is employed in fruit crops such as lemon and mango
Advantages of Asexual Reproduction
- The offspring are genetically similar to their parent which is a great advantages if the organisms are well adapted to their environment
- Agents of pollination are not needed
- Agent of dispersal are not needed
- Greater nourishment is obtained from the parents therefore they can withstand adverse condition
- Since food is ready at hand, the offspring grow and mature quickly
- They can colonise the locality easily
- It is easy to obtain planting material
Disadvantages of Asexual Reproduction
- No variation since parents and offspring are similar from generation to generation
- Bad adaptation of the parents and offspring can lead their death since they are similar genetically
- Since there are no means of dispersal overcrowding, competition, food, space and light may result. This will lead to stunted growth
- There is less chance of evolution
Sexual reproduction is the type of reproduction which involves the fusion of the male gametes and the female gametes to form a zygote which later develop to a young offspring.
Types of Sexual Reproduction
- Conjugation: is a simple types of sexual reproduction which occurs in some lower organisms such as mucor, rhizopus, paramecium and spirogyra. Conjugation is the process by which nuclear material is passed from one cell to another.
In spirogyra, for example, conjugation starts with two filaments called conjugants coming together to lie side by side. lateral outgrowth start to develop opposite each other from opposite cells in the two filaments. The outgrowth meet and the separating well dissolve to form a continuous channel called conjugation tube. The cytoplasm of each cell shrinks away from the cell walls and round up to form gametes.
One of the gametes regarded as migratory move through conjugation tube into the other cell resulting to the fussion of cytoplasm and nucleir of the cells to form zygote. After sometime the zygote develop into zygospore which will germinate to a new filament
Fertilization (fusion of gametes) is defined as the fusion of a minute haplow male gamete (sperm) with a haphoid female gamete (egg) to form a diploid zygote.
In higher animal the gametes are formed in special organ called gonads. The male gamete is called spermatozoa (sperm) which are produced in the testes by a meotic cell division called spermatogenesis. The female gamete is called ovum or egg which are produced in the ovary by meotic cell division called oogenesis. The process of gamete formation either male or female is called gametogenesis. These two type of gametes (male&female) are brought together during mating and they unite by process of fertilization to form a diploid zygote which later develop to a new organism.
In higer plants, male and female gametes are also produced. The flowers are the reproductive units in plants. The male gamete is called pollen grain which are produce by the anther while the female gametes called ovules are produced by the ovary of the flower
Meiosis is the form of division which bring about a halving of the chromosome number as well as an interchange of genetic material between homologous chromosomes. In animal, meiosis takes place at the formation of the gametes and in diploid plants at the formation of spores.
The formation of spores
Meiosis consists of two successive divisions
- 1stMeiotic division: when the parent cell split into two
- 2ndmeiotic division: when the products then divide again giving a total of four daughter cells
1st MEIOTIC DIVISION (REDUCTION DIVISION)
The 1st meiotic division is divided into five stages. These are Interphase, Prophase, Metaphase, Anaphase and Telophase.
INTERPHASE: This is the resting stage of the cell. At this stage chromosome are not seen
PROPHASE: There are three phases of the prophase. These are Early prophase, Middle prophase and Late prophase
Early Prophase: chromosome become visible as long threads
Middle Prophase; Homologous (marching) chromosome become thicker, shorter and clearly visible. Spindle is formed.
Late Prophase: Each chromosome reproduce replice of itself (double stranded). Nuclear membrane starts disappearing. Cross-links called chiasmata (chiasma) are formed between chromosome. Chiasmata help to hold two homologous chromosomes together and also exchange of genetic material (or gene) take place between homologous chromosome which leads to variation or mutation
Nuclear membrane gets dissolved in the cytoplasm. Bivalent chromosomes are arranged at the equator and attached to the spindle by their centromeres.
Each member of the bivalent chromosomes moves apart and moves toward the poles of the cell by the shortening of the spindle
Bivalent chromosomes arrive at the poles of the cell. A new nuclear membrane is formed around each group of chromosomes. Chromosomes uncoil. Nucleolus appear on each nucleus. Nucleus looks granular again. The two nucleic have half the number of chromosomes of the parent cell. This is the reduction division of meiosis. No cleavage of cytoplasm takes place
Chromosome become distinct in the two nucleic centrioles divide, separate and move to the opposite poles of the cell. Spindles are formed.
Nuclear membrane gets dissolved in the cytoplasm chromosomes are attached to the spindle by their centromeres. The two chromatids of the chromosome become more distinct.
The chromosomes get detached at the centromeres. The chromosomes separate and more to the pole.
The chromatids arrive the polls of cells. Nuclear membranes are formed round the four cells. A nucleolus appears in each cell. Spindles get dissolved in the cytoplasm. Cleavage of cytoplasm follows. Four haploid cells are formed at the end of the second meiotic division. Each cell has half the number of chromosomes.
Characteristics of the mother cell hence called haploid (n)
Four daughter cells each contains half (haploid) the original number of chromosome of the parent cell.
IMPORTANCE OF MEIOSIS
1.Meiosis ensures that the fertilized egg (zygote) has a diploid number of chromosome. Therefore, meiosis brings about the reduction of chromosome to half the original number both in the male (sperm) and the female (egg) gametes. For example, every human being has 46 chromosome. During the sperm or egg formation in a process known as gametogenesis, the 46 chromosomes will reduce to 23 chromosomes. When the sperm fuses with the egg, a zygote with 46 chromosomes result.
2.Random assortment of genes during meiosis lead to genetic variation among offspring of the same parents. This is why no two individuals can look exactly alike unless identical twins.
Meiosis can lead to a marked gene change (mutation) which can also bring about variation among individuals.
Life processes involving meiosis
Formation of spermatozoa
Formation of eggs
Formation of pollen grains in flowering plants
Formation of ovules in flowering plants
- Describe two methods of reproduction in unicellular animals you have
REPRODUCTIVE SYSTEM IN MAMMAL
Male Reproductive System
The male reproductive system in man consists of testes, vasa efferenctia, vas deferend (spermdnut penis and glands)
There are two testes in male animal. Each testes is oval in shape and is housed in a wrinkled sac called scrotum which hangs out of the body behind the penis. The scrotum functions as a thermoregulator that protects the sperm from high temeperature. The body temperature is to high for the formation of sperm hence the testes are positioned out of body that is slightly water (2 or 3c lower) than the normal body temperature.
Each testis is made of a large number highly coiled tubes called seminiferous tubules and interstitial cells which lie with the seminiferous tubules. The seminiferous tubules produces the sperm while the interstitial cells produce testosterone.
Vasa efferentia: are small number of tubes which are connected with seminiferous tubules and unite to form epididymis, vasa deference collect sperms from the seminiferous tubules to the epididymis
Epididymis: This is highly coiled tube about 6 metre long which receives sperm from vasa efferentia. Sperm are temporarily stored to mature and develop in the epididymis.
Urethra: it serves as a passage for both urine and sperm
Seminal Reside: the seminal reside is a small sac where sperms are stored. It is located close to the posterior end of vas deferens. It secrets seminal fluid. Seminal fluid contains fructose which provides energy for the sperm.
Gland: Three glands open into the male reproductive system. These are seminal fluid, prostate glant and cooper’s gland.
The prostate gland is located a little below the bladder while a pair of cowper’s gland is situated below the prostate gland. These three glands secret seminal fluid in which sperm swim. The fluid activities sperm and into swimming. It provides food for the sperm and lubricates the passage. The sperm swim freely in the seminal fluid. The acidity of the urine is neutralized by the seminal fluid.
The seminal fluid plus the sperm make up the semen.
Functions of male Reproductive system
- Formation of sperm to fertilize the eggs of the female
- It produces male hormones (testosterone)
FEMALE REPRODUCTIVE SYSTEM
The female reproductive system consists of ovaries, fallopian tube or oviduct, uterus, cervity and vagina and vulva.
Ovaries: These are two oval-shaped structure located in the abdominal cavity on the side of the uterus.
Each ovary is held in position by ligaments. Ovaries are small and short, each contain thousands of undeveloped egg (ova). It is only when a girl has reached the age of puberty (9-15years) that a ripe egg is released alternatively each months by the ovaries. The ovaries stop producing eggs at about the age of 45-55years, a condition referred to as menopause.
- Ovaries produce and release mature egg
- They produce female sex hormones (oestrogene and progesterme)
Fallopian Tube: this arise from the uterus as narrow tube of about (9-13cm) long. The free ends are funnel-shaped free ends are lined with cell having cilia. When an egg is related to the cilia beat to direct the egg into the fallopian tube. Fertilization takes place in this tube
Functions of Fallopian Tube
- Directs the release egg from the ovary to itself
- Fertilization takes place inside the oviduct
- The fertilized egg (zygote) is pushed to the uterus by the cell of the fallopian tub
Ovulation is the release of the egg into the Fallopian Tube by the ovaries.
The uterus is a wide and thick-walled muscular chamber of about 8cm long and 5cm wide. Two fallopian tubes entre into it at the top while the lower narrow part terminates as a neck or cervix. The inner side of the uterus is lined with endometrium (layer well supplied with blood and food to receive fertilized egg)
Function of Uterus
1.Implantation of fertilized egg (zygote): Implantaion is the attachment of the fertilized egg to the wall of the uterus.
2.The uterus provides a place for the attachment of foetal placenta. Before the development of placenta, the uterus provides nutrients for the embryo.
3.Before the development of placenta, the uterus provides nutrients for the embryo
The cervix is a ring of muscle with tiny aperture that closes the lower end of the uterus where it joins the vagina. It controls the opening and clothing of the vagina during birth.
The vagina leads from the cervix of the uterus to the outside of the body. It is an elastic and muscular tube of about 10-14cm long. The opening of the vagina is partially covered by a thin membrane called hymen. If the hymen is intact, it means that the girl is still a virgin. However the hymen can be torn during vigorous physical exercise such as athletics or during sexual intercourse.
Function of the Vagina
- It receives the male penis which deposits sperm into it
- It serves as birth canal during the expulsion of the foetus from the uterus
- The woman menstruate through the vagina
The external female organ are collectively called vulva. These include the two thick fold of skin covered with public hair called labia major, two fold of hairless skin called labia minora
Function of Vulva
- It protects the opening of the vagina
CLITORIS: is a small erectile organ. It is a sensitive organ well supplied with blood vessels and nerves. It causes excitement during sexual intercourse and accelerates organism in female. Like penis it become erective in sexual excitement.
1a. Distinguish between asexual reproduction and sexual reproduction
- Make a fully labelled diagram of female reproductive system
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