​Suggest three factors that could have caused the population change between C and D. 

The first one has been completed for you.

Pesticides may kill soil micro-organisms that decompose humus to release mineral salts. In this
way they interfere with nutrient cycling.

​Overuse of chemical fertilizers and pesticides have effects on the soil organisms that are similar to human overuse of antibiotics. Indiscriminate use of chemicals might work for a few years, but after awhile, there aren't enough beneficial soil organisms to hold onto the nutrients” (Savonen, 1997).

1.  1989 Q4 P1
State how excessive use of pesticides may affect soil fertility
2.  1989 Q8 P1
The table below shows a list of five human diseases. Complete the table by naming the causative agent of each.
The first one has been completed for you.

EVOLUTION
1.      1989 Q7 P1
State the difference between Lamarckian and Darwinian theories of evolution.
2.   1991 Q17 P1
    (a) What is meant by natural selection
    (b) Describe the natural selection brings about adaptation of a species to its Environment
3.  1992 Q5 P1
Two populations of the same species of birds were separated over a long period of   time by an ocean. Both populations initially fed on insects only. Later it was observed that one population fed entirely on fruits and seeds, although insects were available.

Explain the effect of increased physical activity on the following organ systems: 
(a) heart
(b) lungs
(c) kidneys
(d) skin.

Giving examples, describe the following interactions among organisms: 
(a) predator-prey
(b) symbiosis
(c) parasitism.

 The table below shows the rate of product formation for two enzymes, H and J over a range of pH values

(a) On the same axis, plot graphs of the rate of product formation against pH. 
  GRAPH PAPER
(b) Account for the rate of product formation for enzyme H between:
(i) pH 1.0 and 3.0 
(ii) pH 3.0 and 7.0. 
(c) From the graph, determine: .
(i) the pH value at which the rate of product formation of the two enzymes was the same 
(ii) the value of the rate of product formation for enzymes H and J at the pH value stated in (c)(i) above 
(iii) the optimum pH value for enzyme J 
(d) State one variable that may lead to the change in the optimum rate of product-formation of the two enzymes. 
(e) Suggest with a reason, the likely part of the human alimentary canal where enzyme H would be found.

 A person accidentally touches a hot pan and responds as illustrated in the diagram below.

(a) Explain how the response illustrated above occurs. 
(b) Explain how auxins are utilised as selective weed killers in agriculture.

In cats, the gene for fur colour is sex-linked. Letter G represents the gene for ginger fur colour while letter B represents the gene for black fur colour in a given cat species. These genes are co-dominant. Heterozygous females have ginger and black patches of fur and their phenotype is described as tortoise-shell.

​(a) With reference to the information given above, what is meant by the term co-dominance? 
(b) Explain why male cats with a tortoise-shell phenotype do not usually occur. 
(c) A tortoise-shell female was crossed with a black male. Determine the genotypes and phenotypes of the offspring.

 In an experiment, students treated seedlings as illustrated below.

​(i) Account for the observations made in seedling I. 
(ii) Explain the similarity in the end results made in seedlings II and III. 
(iii) State the likely treatment that would make seedlings II and III respond like seedling I.

K.C.S.E Biology Q & A - MODEL 2019PP2QN03

The table below shows results of blood cell counts per mm3 of blood from a sample of people living at different altitudes.

​(a) Explain the relationship between:
(i) red blood cells count and the altitude; 
(ii) white blood cells count and the altitude. 
(b) Explain why chances of nose-bleeding increase with altitude in humans.

In an experiment to investigate the effect of sodium chloride on the growth rate in a spinach seedling, seeds were treated with different concentrations of sodium chloride. The results are as recorded in the table below.

​(a) From the results in the table above, explain the effect of increasing the concentration of sodium chloride. 
(b) Apart from a ruler, state two other equipment one would need to determine the rate of growth in the roots. 
(c) With a reason, state one other part of the seedling the students would focus on to determine the effect of sodium chloride on growth. 
(d) State the likely effect on the seedling of increasing the concentration of sodium chloride to 2.20mol/l

 State one characteristic of muscles responsible for each of the following:
(a) peristaltic movement 
(b) movement of limbs