Question Library

No expanded working has been attached for this question yet. The verified answer is Option C.

No expanded working has been attached for this question yet. The verified answer is Option B.

No expanded working has been attached for this question yet. The verified answer is Option E.

Two key organelles directly involved in mitotic cell division are the centrosome (which contains centrioles) and the nucleus. The centrosome, with its centrioles, helps organize the mitotic spindle, while the nucleus houses and organizes the genetic material (chromosomes) during the division process. Centrioles are cylindrical structures found in animal cells and are essential for cell division. They organize the mitotic spindle, a structure that ensures accurate chromosome separation during mitosis.

No expanded working has been attached for this question yet. The verified answer is Option D.

No expanded working has been attached for this question yet. The verified answer is Option A.

No expanded working has been attached for this question yet. The verified answer is Option E.

(a) Sense organ: A sense organ is an organ made up of a group of specialized cells/tissues/receptors , which is able to receive/collect/perceive/detect stimulus and transmit the information/impulse/message to the nervous system. (b) Sense organs in mammals: Nose/olfactory organ; eye; ear; tongue; skin. (c) When a person spins and stops: Endolymph, in the inner ear/semi circular canals continues to move causing sensory hairs/sensory cells to be stimulated. impulses reaching the brain/cerebellum through the auditory nerve show that the person is still spinning the brain interprets the body as still moving - and confusion is imposed on the receptors - sensitive to position - giving the person an impression of dizziness. (d) Functions of: (i) Cerebellum - Receives impulses from the ear; involved in balance and posture; coordinates voluntary muscles. (ii) Cerebrum - Controls voluntary actions/any other correct example; concerned with memory; intelligence. (iii) Medulla Oblongata: Controls involuntary/reflex actions; heartbeat; coughing; sneezing; blinking/any other correct involuntary actions.

(a)Why an athlete should be given glucose drink: Glucose is the simplest form of carbohydrates/soluble form of carbohydrate; an energy-giving food substance which does not require any form of digestion. - hence it is absorbed in the ileum/small intestine. - where it diffuses/enters into the blood stream/circulatory system. - it is then assimilated; and oxidized. - within the shortest time/quickly/immediately. - to give energy to the athlete. - bread is a complex carbohydrate/polysaccharide/starch. - which will require a series of digestive processes/hydrolysis. - which starts in the mouth; and ends in small intestine/ileum. - this takes a longer time to produce energy for use/cannot give immediate energy. (b) Test for starch: - Macerate/crush a piece of the food substance. add water to the crushed food to form a solution/suspension/take a piece of food substance. put a few drops of the solution/suspension/ piece of food. on a white tile/watch glass/in test tube add one or two drops of iodine solution the solution/piece of food will turn blue black indicating the presence of starch. (c) Importance of water in human diet: - Water is an essential part of living protoplasm; blood it acts as a solvent; and transport medium in the body for food substances/gases/hormones. transports waste excretory products it is a medium for chemical reactions/digestive processes it function in distribution of body heat it is the main component of the synovial fluid of joints; amniotic fluid serves a protective function in the brain allows easy movement of food through the digestive tract.

Food chain: This is a linear feeding relationship; in which energy is transferred from producer/plants; through a series of organisms/trophic levels; in which each organism feeds on the preceding one; and provides food for the succeeding one in the habitat. Terrestrial food chain: Terrestrial organism correctly named (TN) - Producer listed first correctly named primary consumer; secondary consumer; and tertiary consumer/decomposer; correct direction of arrows (CA) (c)(i) Flow of energy: Energy flow is unidirectional/non-cyclic; it is either utilized; or stored. Light energy from the sun is absorbed by chlorophyll in green plants; and used in photosynthesis to produce carbohydrates; the chemical energy in the carbohydrate is passed down the food chain; when the primary consumers feed on the plants/producer; the chemical energy is passed along the food chain to the secondary consumer; and then to the tertiary consumer/decomposer. (ii) Energy loss: - Energy is lost at each tropic level - when a herbivore/primary consumer feeds on a plant/producer; not all parts of the plant is eaten; as a result not all the energy in the plant/ producer is consumed; plants lose energy via respiration, do not utilize all the energy present in preceding members; energy is also lost in respiration; excretion, movement; and other metabolic activities.

(a) Variation: These are morphological; and physiological differences; which occur within a species which could be hereditary or acquired from the environment. (b) Advantages of variation: - Appearance of new varieties - variation allows survival of the fittest - competition arises - nature selects the most adapted varieties - that are more resistant to diseases - and better adapted to changes in the environment. (c) Differences between continuous and discontinuous variation continuous Discontinuous caused by co-dominance caused by complete dominance Intermediates are present No intermediate characteristic Affected by the environment not affected by the environment They are controlled by genes /polygenes Not polygenic Follow the normal distribution curve/frequency of characteristics evenly distributed Not evenly distributed (d)(i) Sex-linked characters: These are characteristics associated with the sex of an individual; the gene for the expression of the character; is borne on one of the sex/the X chromosomes. (ii) Co-dominance: This is a condition in a heterozygote; in which both alleles have equal dominance; and the phenotype is a mixture of the opposing characters. (iii). Hybrid vigour: This is the production of new varieties within a species; which are healthier/have greater resistance to diseases/are better adapted to the environment; as a result of out breeding/crossing non related members of a species.

(a) Water cycle Condensation in clouds Precipitation/Rainfall Evaporation of water from water bodies/river/sea/ ocean Evaporation of water from soil/ground Excretion by animals Drinking of water by animals Perspiration/sweating/respiration by animals Erosion/run-off of water from soil/ground Decay in plants/ animals. (b) Experiment: -A young herbaceous plant/balsam/water leaf/ plant is uprooted/cut a twig of a young herbaceous plant under water - the cut twig/the roots are washed with water; to remove the soil particles -a solution of a dye/eosin/red ink is made in a beaker - the roots of the plant/cut twig is immersed in the solution. - and set up exposed to sunlight -and allowed to stand for one to six hours -remove the plant from the solution and wash the roots/stem/of twig thoroughly - make transverse sections of the root/stem - observe the sections under the microscope - it will be observed that only the xylem tissues pick the dye/is stained re-indicating that water is conducted in the xylem tissues.

(a) Growth: Irreversible/permanent increase; in size/dry mass/weight; due to the addition of living protoplasmic material. (b)i Growth in plants Growth in animals -Mainly restricted to growing regions/apical meristem -Continuous throughout life (in growing regions) -Indefinite number of parts -Diffuse/takes place in all parts of the body/intercalary - limited to a certain period in life -Definite period of part (ii) Metamorphosis Housefly Toad -Takes place on land -Pupal/resting stage present -Takes shorter time -takes place in water -No pupal/resting stage -Takes longer time (c) & (d) Names of growth hormones and their effects (i) Plants: Cytokinins - Stimulates lateral buds into branches - Promotes growth of lateral roots - Cell division in apical meristems; elongation - Breaking dormancy in seeds Auxins - Rapid cell division of apical region of shoots; elongation Gibberellins - Cell elongation; stimulates growth in dwarf varieties; induces dormant seeds to germinate - increases fruit size. Animals: Thyroxin - Regulates growth and development of cells. Growth hormones from pituitary gland - Stimulates growth of long bones.. Sex hormones any correctly named sex hormone -Stimulates growth of sex organs. (e)(i) Monocotyledons - Hypogeal germination (ii) Dicotyledons - Epigeal germination. (f) Differences between Epigeal germination Hypogeal germination Testa splits pericarp splits Hypocotyl emerges uncovered Hypocotyl covered by the sheat/coleorrhiza cotyledons are carried above the soil cotyledons remains in the soil Energy obtain from food stored in the cotyledon energy obtained from food stored in the endosperm hypocotyl elongates epicotyl elongates cotyledon is the first photosynthetic tissues foilage leaves are the first photosynthetic tissue

(a) Habitats of specimens A, B and C: A/Water lettuce - On the surface of ponds/lakes/streams. B/Cactus-Deserts/savannahs/dry/arid regions/along the sea coast. C/Talinum- Farmland/gardens/wet lands/waste land/any other appropriate habitat. (b)(i) Observable features: A/Water lettuce-Broad aerial leaves- Numerous adventitious roots - Leaves and stem green Slender stem/stolon -Hairs on surface of leaves -Rosette arrangement of leaves -Spongy leaves. B/cactus - Leaves modified into spines-Succulent stems- Thick waxy cuticle on stems- are green/chlorophyllous - Flattened stem. C/Water leaf/Talinum sp/Amarantus sp-Well developed root/taproot system - Numerous green leaves - Erect stem-Swollen taproot (for Talinum sp). (c) Observable features of A, B and C: A/Water lettuce - Broad aerial leaves/rosette arrangement of leaves makes it buoyant/receive maximum sunlight for photosynthesis - Numerous adventitious roots/root hairs for absorption of water and mineral salts/aids floatation - Leaves and green/chlorophyll for photosynthesis -Slender stem/stolon that offer minimum resistance to water currents -Hairs on surface of leaves prevent water from blocking stomata/aiding photosynthesis/respiration Buds on stem/stolon for vegetative propagation - Spongy leaves aid buoyancy. B/Cactus-Flattened stems to receive maximum light - Leaves modified into spines to prevent water loss - Succulent stems for water storage - Possession of thick waxy cuticle on stem to reduce water loss by transpiration. - Stems are green/chlorophyllous for photosynthesis. C/Water leaf/Talinum sp/Amarantus sp - Well developed root/taproot system for anchorage and water absorption - Possession of numerous green leaves for photosynthesis - erect stem hold the leaves to receive maximum sunlight. -Talinum has swollen taproot for storage. c) Observable differences between A & C: A/Water lettuce C/Talinum sp/Waterleaf/Amarantus sp Adventitious root system Tap root system Horizontal stem/stolon Erect stem Hairs on leaves Hairless leaves/smooth surface Leaves borne in a rosette Leaves arise singly on the stem Absence of branches Branches present Flowers absent Flowers present (d) Drawing of specimen C/Talinum sp/Amaranthus sp:-Prominent taproot

b) Description of graph: Initially the rate of production of new pineapple shoots increases; with Increased concentration of cytokinin -Shoot development reaches its peak at optimum concentration of cytokinin/4.5mg/l - Above this concentration, shoot development declines/decrease.