Mastering KCSE Biology with Comprehensive Topical Questions and Answers
K.C.S.E Biology Q & A - MODEL 2012PP2QN08
Using a relevant example, describe how an allergic reaction occurs in a human being.
ANSWERS
​An allergic reaction is a hypersensitive response; to an antigen by the body immune
system; The body immune system responds by overproducing antibodies; against harmless antigens; The antigen-antibody reaction occurs on the surface of body cells; which burst open; and release histamines; Histamines cause inflammation/itching! swelling/pain, et.c; which damage the body; Allergic people are hypersensitive to materials like dust/pollen grains/some foods/some drugs/some pollutants,
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K.C.S.E Biology Q & A - MODEL 2012PP2QN06
The data provided below represent populations of a predator and its prey over a fifty years’period.
​(a) (i) Using the same axes, draw graphs of the relative populations of P and Q against time.
(ii) With a reason, identify the curve that represents the prey. (iii) Account for the two populations between 25 arid 32 years. (iv) Which years were the two populations equal? (v) A part from predation, state three biotic factors that may have led to the decline of the prey population. (b) Describe the hazards of air pollution by Sulphur (IV) Oxide.
answers
(a) (i) title - Graph of Prey-predator relationship; (OWTE)
Scales X axis; Graph should cover more than half of the grid provided. Y axis; Graph should cover more than half of the grid provided. correct plotting P; Q; smooth curves P; Q; labelling axes;
(ii) P represents the prey;
Prey population is initially higher prey population usually starts falling earlier; (iii) Both populations decrease; because prey is not enough to sustain predator/population environmental stress limit population of prey; (iv) at 23±0.5 years; and at 39±0.5; (v) less food for the prey/intra specific competition; emigration of the prey; diseases causing death of the prey; parasitism; human activities b)sulphur dioxide in the air - causes respiratory diseases; poisons plants; forms acid rain which increase soil pi-J; corrodes metals in buildings; K.C.S.E Biology Q & A - MODEL 2012PP1QN25
State the role of the following hormones in the life cycle of insects:
ecdysone hormone; . juvenile hormone.
answers
K.C.S.E Biology Q & A - MODEL 2012PP1QN24
State four characteristics of apical meristem cells.
answers
K.C.S.E Biology Q & A - MODEL 2012PP1QN21
Name the process through which free atmospheric nitrogen is converted into nitrates.
answer
K.C.S.E Biology Q & A - MODEL 2012PP1QN20
State three aspects that can be used to estimate growth in seedlings
answers
K.C.S.E Biology Q & A - MODEL 2012PP1QN17
Name two substances that leave the foetal blood through the placenta.
answers
K.C.S.E Biology Q & A - MODEL 2012PP1QN15
What name is given to a group of hormones that controls the development of secondary sexual characteristics in a human male?
answer
K.C.S.E Biology Q & A - MODEL 2012PP1QN05
The table below shows results of a study of three plants C, D and E growing in different habitats.
(a) Which one of the plants C, D and E grows in an area of relatively low water availability?
(b) Explain your answer in (i) above.
answers
​(a) Plant C;
(b) Thick cuticle reduces water loss; Low number of stomata reduces water loss; Large root-surface area enhances water absorption; K.C.S.E Biology Q & A - MODEL 2011PP2QN06
An experiment was carried out to investigate the population of a certain micro-organism. Two petri-dishes were used. Into the petri-dish label led M, 60cm3 of a culture medium was placed while 30cm3 of the same culture medium was placed in petri-dish labelled N. Equal numbers of the micro-organisms were introduced in both petri-dishes. The set-ups were then incubated at 35°C. The number of micro-organisms in each petri-dish was determined at irregular intervals for a period of 60 hours. The results were as shown in the table below.
(i)On the same axes, draw the graphs of relative number of micro-organisms against time on the grid provided.
(ii) After how many hours was the difference between the two populations greatest? (iii) Work out the difference between the two populations at 50 hours. (iv) With a reason state the effect on the population of micro-organisms in petri-dish M if the temperature was raised to 60°C after 20 hours. (v) Account for the shape of the curve for population in petri-dish N between 46 hours and 59 hours.
answers
​(ii) 42 hours;
(iii) Graph M at 50 hrs is 1220 ± 20. Graph N at 50 hrs is 540 ± 20 (2 m 1220-540=680±4; (iv) Population growth stops; . High temperatures kill the microorganisms/denature enzymes; (v) 46 hours to 59 hours death rate of the microorganisms is higher, than their population growth rate; due to exhaustion of nutrients; and accumulation of toxic wastes; K.C.S.E Biology Q & A - MODEL 2011PP2QN05
The diagram below represents a flower.
(i) On the diagram, name two structures where meiosis occurs.
(ii) How is the flower adapted to prevent self-pollination? (ii) How is the flower adapted to prevent self-pollination? (b) The diagram below represents a human reproductive organ.
​(i) Explain two adaptations of the structure labelled L to its functions.
(ii) Explain the role of the gland labelled K.
answers
​(a) (i) Anthers; Ovary;
(ii) Anthers are below the stigma to minimise self pollination;
production; it has many, long and coiled seminiferous tubules to increase the surface area for production/storage of sperms; (ii) K produces an alkaline fluid that neutralizes acid in the vagina; this fluid contain nutrients for the sperms; and also activates sperms;
K.C.S.E Biology Q & A - MODEL 2011PP1QN29
State four reasons why water is significant in seed germination.
ANSWER
K.C.S.E Biology Q & A - MODEL 2011PP1QN28
State two ways by which auxins regulate growth in seedlings.
ANSWERS
K.C.S.E Biology Q & A - MODEL 2011PP1QN26
Name the gamete cells that are produced by the ovaries.
ANSWERS
K.C.S.E Biology Q & A - MODEL 2011PP1QN23
The diagram below represents a transverse section of an ovary from a certain flower.
a) (i)Name the structure labelled W.
(ii)Name the type of placentation illustrated in this diagram. (b) Give an example of a plant whose flowers have the type of placentation named in (a)(ìi) above.
ANSWERS
(a) (i) Ovule;
(ii) Axile placentation; (b) Orange or any correctly named citrus plant; K.C.S.E Biology Q & A - MODEL 2011PP1QN14
The diagram below represents a certain plant.
​(a) What is the likely habitat for the plant?
(b) Give two reasons for your answer in (a) above.
answers
​(a) Dry/Arid/Semi-arid/Desert;
(b) Succulent/ fleshy stem; reduced leaves/leaves reduced into thorns/leaves modified into spines/spikes; K.C.S.E Biology Q & A - MODEL 2011PP1QN06
What is meant by the following terms?
(a) Ecology. (b) Carrying capacity.
answers
​(a) This is the study of the inter-relationship between organisms and their environment;
(b) The maximum population of a species than a particular habitat can support; without depletion of resources. K.C.S.E Biology Q & A - MODEL 2011PP1QN05
The figure below illustrates a food web in a certain ecosystem.
From the food web:
(a) draw the shortest food chain; (b) identify the organisms with the highest (i) number of predators; (ii) biomass.
answers
(a) Grass > Grasshopper >- Lizards;
(b) (i) Chicken; (ii) Grass;
K.C.S.E Biology Q & A - MODEL 2010PP2QN07
Describe die process of fertilization in flowering plants.
answers
​Pollen grains land onto the stigma; and adhere to it as a result of the stigma cells secreting a sticky substance; It absorbs nutrients; and germinates forming a pollen tube; The pollen tube grows down the style to the ovary; deriving nourishment from surrounding tissues; The pollen tube has tube nucleus at the tip; and generative nucleus immediately behind it; As the tube grows downwards into the ovary the generative nucleus divides mitotically; to give rise to two nuclei; which represent the male gametes; The pollen tube penetrates the ovule/embryo sac through the micropyle/chalazza; After the pollen tube enters the embryo sac, the tube/vegetative nucleus breaks down; leaving a clear passage for the entry of the male nuclei;
which enter the embryo sac; where one fuses with the egg cell nucleus; to form a diploid zygote; which develops into an embryo; The other male nucleus fuses with the two polar nuclei; to form a triploid nucleus/primary endosperm nucleus; Which becomes endosperm; This type of fertilization is called double fertilization; K.C.S.E Biology Q & A - MODEL 2010PP2QN03
The diagram below represents a food web in a certain ecosystem.
(a) Name the trophic level occupied by each of the following:
(î) caterpillars; (ii) small insects. (b) From the food web, construct two food chains which end with lizards as a tertiary consumer. (e) (i) Which organisms have the least biomass in this ecosystem? (ii) Explain the answer in (c) (1) above.
ANSWERS
​(a) (i) Primary consumers;
(ii) Primary/secondary consumers; (b) Green plants — Caterpillars — Lizards; Decaying leaves —Caterpillars — small insects — Lizards; (e) (i) Hawks; (ii) At each trophic level energy is lost as heat in respiration; and during decomposition; lost in defecation/faeces/ waste products or metabolism/excretion; some parts of organism not eaten e.g. feathers; K.C.S.E Biology Q & A - MODEL 2010PP2QN01
In an experiment, disinfected soaked bean seeds were put in a vacuum flask which was then fitted with a thermometer as shown in the diagram below.
The temperature readings were taken every morning for three consecutive days.
(a) Which process was being investigated? (b) (i) What were the expected results? (ii) Account for the answer in (b)(i) above, (c) Why were the seeds disinfected? (d) Why was a vacuum flask used in the set-up? (e) How would a control for this experiment be set?
answers
(a) Respiration;
(b) (i) Increase/rise in thermometer reading/temperature; (ii) Carbohydrates/starch/glucose in germinating seeds is broken down/oxidised to get energy; some of the energy is released as heat; (which increases temperature reading). (c) To kill bacteria/fungi/microorganisms; that would cause decay/decomposition/respiration of the beans; (d) To conserve heat/prevent heat loss to surroundings; (e) Use similar set-up but with dead and disinfected beans seeds/ use dead disinfected bean seeds/use dry bean seeds;
K.C.S.E Biology Q & A - MODEL 2010PP1QN30
What is meant by the term apical dominance?
answer
K.C.S.E Biology Q & A - MODEL 2010PP1QN25
State three factors that contribute to the deceleration phase in the population curve of an organism.
answers
K.C.S.E Biology Q & A - MODEL 2010PP1QN22
What is the function of the following structures in the human reproductive organs?
(a) Fallopian tubes. (b) Epididymis. (c) Scrotal sac.
answers
(a) Passage of ova;
(b) Storage of sperms; (c) Hold the testis;
K.C.S.E Biology Q & A - MODEL 2010PP1QN20
State two advantages of internal fertilization in humans.
answers
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