2021 WAEC Biology Essay And Objective Question and Answer

2021 WAEC Biology Essay And

Objective Question and Answer 1. Where are most nitrogen compounds excreted from humans? A. kidneys B. liver C. rectum D skin. 2. A motor neurone transmits impulses from A muscle to the spinal cord. B receptor to muscle. C receptor to the spinal cord. D spinal cord to muscle. 3. In which order does light pass through these structures in the eye? A. cornea → aqueous humour → lens → vitreous humour → retina B. cornea → vitreous humour → lens → aqueous humour → retina C. lens → aqueous humour → cornea → vitreous humour → retina D. lens → vitreous humour → cornea → aqueous humour → retina. 4. A person with Down’s syndrome is born with 47 chromosomes in each cell, instead of 46. What could cause this? A. A mutation happened during the production of the egg cell. B. More than one sperm fused with the egg at fertilisation. C. Radiation caused a change in the structure of a gene in the father’s sperm. D. The mother was exposed to harmful chemicals while she was pregnant. 5. A redflowered plant is crossed with a whiteflowered plant. All the offspring have red flowers. What is the genotype of these offspring? A. RR and Rr B. RR only C. Rr only D. rr only. 6. A plant has flowers whose anthers mature and fall off before the stigma is fully developed. What will this prevent? A. cross-pollination B. insect-pollination

C. self-pollination D. wind-pollination. 7. The cell wall of a plant cell is removed using an enzyme. What would happen if this cell is then placed in distilled water? A. It would take longer for the cell to become turgid. B. Proteins in the cytoplasm would leave through the cell membrane. C. The cell would become smaller as water passes out. D. The cell would burst as water moves into it. 8. Some organisms live at the bottom of the seas where it is very dark. To synthesise glucose, they use energy from chemicals in the very hot water that comes out of volcanoes. What is a distinguishing feature of these organisms? A. Their enzymes are easily denatured by heat. B. They do not need carbon dioxide. C. They do not need to be green. D. They obtain energy only as carnivores. 9. Under which set of conditions will the transpiration rate of a well-watered plant be fastest? A. a cool, dry, windless day B. a cool, rainy, windy day C. a hot, dry, windy day D. a hot, rainy, windy day. 10. Why is glucose found in the urine of diabetics? A. increased uptake and use of glucose by the body cells B. not enough glucose in the blood is converted to glycogen C. stored fats in the body are being oxidized D. too much glucose is absorbed by the kidney cells. 11. Which bones form a joint at the shoulder? A. humerus and scapula B. humerus and ulna C. radius and ulna D. radius and scapula. 12. Which sequence describes the flow of energy in an ecosystem? A. carnivore → herbivore → plant → Sun B. plant → herbivore → carnivore → Sun C. Sun → carnivore → herbivore → plant D. Sun → plant → herbivore → carnivore. B 1. a. (i) What is respiration? (ii) In a tabular form, state four differences between gaseous exchange and aerobic respiration. b. (i) Explain the term residual air. (ii) What is the importance of residual air to mammals? (iii) State four characteristic features associated with respiratory structures. c. (i) What is oxygen debt? (ii) Outline three activities that can result in oxygen debt. ANS: (a) (ii) Differences between gaseous exchange and aerobic respiration Gaseous exchange – Aerobic respiration -oxygen simply moves into the – oxygen is used to oxidise glucose organism and CO2 moves out; -the process takes place outside the cells process occurs inside the cells -physical process chemical process -no energy is released -no enzymes involved (b) (i) Residual Air. During breathing out/ expiration/ exhalation; not all the air is removed from the lungs; the air left inside the lungs during breathing out is residual air. (ii) Importance of Residual Air. Air is left in the lungs so that the lungs do not collapse; the air is always left inside the lungs so that more oxygen can be removed (diffuse) into the bloodstream. (d) (i) Oxygen debt. The build-up of lactic acid; during strenuous exercise is poisonous and makes the muscles ache; oxygen is needed to break down/get rid of the lactic acid; that is why athletes continue breathing heavily even after the exercise is over; the oxygen needed to get rid of the lactic acid is known as oxygen debt. (ii) Activities that can result in oxygen debt. Running; boxing; swimming /any correct example of strenuous activities. 2. a. What is photosynthesis? b. List: (i) four external factors; (ii) two internal factors; that affect the rate of photosynthesis. c. (i) List the major products of the light-dependent stage of photosynthesis. (ii) State the importance of each of the products listed in 2(c) (i) above. d. (i)Explain why there are no green plants at the lower depths of some lakes. (ii) State why decomposers are important to flowering plants. 3. (a) Explain the following terms: (i) disease; (ii) symptoms of diseases (b) (i) List two physical and two chemical barriers that prevent pathogens from penetrating the body of an organism. (ii) Explain how vaccination protects the body from contracting infectious diseases. (c) Distinguish between an antibody and an antigen. (d) Name the causative agents of: (i) Malaria; (ii) Cholera; (iii) AIDS. 4. (a) (i) What is excretion? (ii) List the excretory organs in humans and name one waste product excreted by each organ. (b) How does the mammalian kidney function as an excretory organ? (c) Name the excretory organs in (i) insects; (ii) earthworms. 5. (a) (i) What is conservation? (ii) State six factors responsible for the decline of the abundance and variety of wildlife. (b) Outline six ways in which the government can improve the situation in 5(a) (ii) above. (c) (i) What is Eutrophication? (ii) State two causes of eutrophication. 6. (a) Describe the carbon cycle. (b) State the functions of: (i) nitrogen fixing bacteria; (ii) nitrifying bacteria; (iii) denitrifying bacteria; in nature. ANS: (a) Carbon occurs in the air/ atmosphere/as carbon dioxide/dissolved in the oceans /seas/ water bodies, and is circulated continuously; through the activity of microorganisms /decay bacteria/ saprophytic organisms /fungi; which decompose the dead organisms; plants /animals release carbon dioxide and water; the carbon dioxide released increases the concentration of carbon in the atmosphere /ocean/ sea /water bodies; this is further increased by respiration in plants and animals; combustion of wood/ coal/ oil/ fuel; some of the excess carbon dioxides is absorbed by the sea /water bodies and also used by plants in photosynthesis; organisms in seas /oceans /water bodies release carbon dioxide into the atmosphere/ water. (b) Functions of – (i) Nitrogen-Fixing Bacteria; Nitrogen-fixing bacteria in the nodules of legumes; those living freely in the soil; convert atmospheric nitrogen; into ammonia /ammonium compounds. (ii) Nitrifying Bacteria; They live freely in the soil; oxidize/breakdown the ammonium compounds; to nitrites; which are then oxidized by others/ Nitrobacter/ named bacteria; to nitrates. (iii) Denitrifying Bacteria; They live freely in the soil; these break down/ oxidize ammonium compounds; into nitrogen; and oxygen; which is released into the atmosphere. 7. (a) (i) What is a gene? (ii) Differentiate between the terms genotype and

phenotype. (b) Explain the following terms: (i) hybrid; (ii) pure breeding; (iii) nucleotide. (c) In garden pea seeds, a smooth seed coat is dominant over a rough seed coat. With the aid of a genetic diagram, determine the result expected if a homozygous rough pea is crossed with a smooth seed coat plant whose parent were rough-coated. 8. (a) (i) Describe epigeal germination of a seed. (ii) In a tabular form, state three differences between epigeal germination and hypogeal germination. (b) (i) What is seed dormancy? (ii) State three ways by which dormancy in seeds can be broken. (c) State six advantages of using contraceptives in human populations. 9. Keep refreshing this page and bookmark it for current answers as we upload them here.