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.
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Cold daysContraction of erector pilli muscles; hair raised hence the dog appears larger/vasoconstriction Hot daysRelaxation of erector pilli muscles, hair lies flat hence the dog appears smaller;/ vasodilation |
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Pesticides may kill soil micro-organisms that decompose humus to release mineral salts. In this
way they interfere with nutrient cycling.
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.
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.
Human Diseases
K.C.S.E Biology Q & A - MODEL 2019PP2QN07
Giving examples, describe the following interactions among organisms:
(a) predator-prey
(b) symbiosis
(c) parasitism.
(a) predator-prey
(b) symbiosis
(c) parasitism.
answers
​.(a) Predator-Prey
- -Predator is an animal that hunts/kills another/ other animals(prey) for food;
- -A dog and a hare; (acc. either correct examples)
- Preys desire survival mechanism in their habitats not to be eaten/killed; to survive and reproduce/propagate this in linage; to this end (prey)(adaptations)
- -They run faster (strong hind muscles);
- -Camouflage with environments;
- -Mimic the predators; (acc. some have a wider field of view/vision;)
- -Some emits some chemical/smell that turn of predators;
- -Others like porcupine use quills/ spikes/spines to fight off predators;
- -Some have good sense of smell to detect predators; on the other hand, predators also evolve/desire means to be able to survive in such an ecosystem for instance.
- -Running faster; strong jaws/long/sharp canine/talons;
- -Camouflaging with the environment;
- -Mimicking prey
- -Sharp eyesight;
- -Strong sense of smell
- -Produce venom/poison that paralyze/kill prey.
- A close (long term) association between two organisms of different species where the two mutually benefit from each other;
- Example; The bacteria in the rumen/gut of herbivores; which help herbivores digest cellulose; as they are sheltered by the herbivores;
- -The bacteria found in the human digestive system/gut/colon
- -the bacteria are sheltered by humans;
- -The bacteria aid human in synthesis of vitamin K/ B12/enzyme microbial balance;
- -The nitrogen fixing bacteria on the root nodules of legumes;
- -NFB benefits from shelter offered by the plant;
- NFB facilitate conversion of free atmospheric Nitrogen into forms that can be readily used by the plants;
- A kind of (inter-specific) relationship/Association where one member/organism, the parasite, benefits while the other the host is harmed/loses; Also called antagonistic symbiosis)
- Example;
- A tick (parasite) sucking blood /Nutrients from a cow (host); making the cow to be anaemiac/skin destroyed/malnourished/transmission of diseases;
- Parasite can be external/Exo-Parasite; or internal/ endo-parasite; e.g. liver fluke
- Example- Liver fluke sucks blood/Nutrients from host and cause death/bodily harm on the internal Organs of the host including blocking blood vessels
K.C.S.E Biology Q & A - MODEL 2018PP1QN13
State two limitations of using a quadrat to estimate the population of organisms.
ANSWERS
- Cannot be used for most animals/plants;
- Assumes organisms are evenly distributed;
- Inaccuracy (over/under-estimation);
K.C.S.E Biology Q & A - MODEL 2017PP2QN07
Explain the importance of protecting the forest ecosystem with reference to the following:
(a) climate change
(b) biodiversity
(c) biotechnology
(d) water conservation
(e) pollution.
(a) climate change
(b) biodiversity
(c) biotechnology
(d) water conservation
(e) pollution.
answers
a) Climate change
- Promote(regular) rainfall/precipitation/prevent desertification;
- Act as wind breakers;
- Keep earth temperatures cool/reduce global warming;
- Keeps biogeochemical cycles going e.g. hydrological, carbon,nitrogen, phosphorous, sulphur cycles;
- Conserve diverse flora/ fauna;
- Conserve genetic variety;
- Prevent extinction of rare species;
- Source of research/employment;
- Aesthetic/attracting tourism in foreign exchange;
- Have impact on culture/religion/politics; ‘
- Food and shelter for other organisms and man;
- Source of oxygen;
- Manufacture of medicines/directly used as medicinal;
- Source of food/food products;
- Provide fuel (when regulated);
- Provide paper and related by-products (when regulated);
- Provide timber (when regulated);
- Products used in other industries e.g. tannin, wax, rubber, oil, honey;
- Increased ground water/high water tables;
- Adds into rivers/lakes/permanency ¡n existing water bodies/reservoirs;
- Water towers/water catchment;
- Minimize soil pollution/ensuring cover against surface run-off/wind erosion/denudation;
- Trees/vegetation clean the soil surface by absorbing nutrients from decomposed matter e.g. sewage;
- Large scale clean-up of polluted air/dust;
- Muffle noise pollution;
K.C.S.E Biology Q & A - MODEL 2016PP1QN21
​The figure below illustrates a food web in a certain ecosystem.
​From the food web:
(a) Draw the shortest food chain
(b) Identify the organism with the highest:
(i) number of predators
(ii) biomass
(a) Draw the shortest food chain
(b) Identify the organism with the highest:
(i) number of predators
(ii) biomass
answers
K.C.S.E Biology Q & A - MODEL 2016PP1QN20
State three factors that contribute to the deceleration phase in the population curve of an organism.
answers
- Overcrowding
- Accumulation of toxic wastes
- Limited resources such as nutrients
K.C.S.E Biology Q & A - MODEL 2016PP1QN12
Other than using the quadrant, give two methods of estimating population of grass.
answers
- Belt transect
- Line transects
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