A group of students carried out a study of the population growth of flour weevils. They put 16 grams of maize flour into two equal boxes K and L respective . They then introduced equal numbers of weevils into the boxes. The boxes were kept under similar environmental conditions. The weevils were counted at intervals and the results recorded in the table below.
(a) Using a suitable scale ,draw two graphs on the same axes from the results in the table.
Plot approximate number of weevils present on the Y – axis( Use graph paper provided) (8mks)
(b) What were the approximate number of weevils present in the two boxes on the 70th day. (2mks)
Number in K: ..
Number in L:......
K - 555
L - 1020
(c) (i) On what day was the population of weevils in K 580. (1mk)
(ii) Between which days was the population difference greatest . (1mk)
100 - 120
(d) Account for the shape of graph L between day 5 and day 100. (4 mks)
Increase in population; because there is adequate food; the number of reproducing individuals is increasing; wastes products have not accumulated to toxic levels.
(e) State factors that would make the human species assume the graph curve above in K. (4mks)
The diagram below shows a specialized cell from a human being.
(a) Identify the cell. (1mk)
(b) Name the parts labelled A,B, and C. (3mks)
(c) State the functions of the part labeled D. (1mk)
Propels the sperm forward
(d) A student observed cells under a microscope and counted six (6) cells a cross the diameter of view. The diameter of field of view was found to be 1.25mm. Calculate the length of one of the cells observed. ( Answer in micrometer). (3mks)
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.
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.
(i) Positive phototropism/tip bends towards light; light causes migration of auxins (produced at the tip) to the darker sides; (of the shoot) resulting in faster division of cells/ elongation/growth on the darker /opposite side of the shoot hence bending towards light
(ii) both seedlings remain upright; ( erect) seedling II does not have tip while seedling III the tip has been covered by opaque material preventing light causing unequal distribution of auxins; . uniform/even distribution of auxins)
(iii) Fitting a gar block treated with auxins at the decapitated end of seedling II; Removing the opaque material covering the tip of seedling III/ replacing the opaque cap with a transparent one;
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