ECOLOGY DISCUSSION QUESTIONS

(A) DATA BASED QUESTIONS

1. Graph in the figure below shows the effect of sewage discharge on some
chemical constituents of a river at increasing distances downstream from
the point of sewage discharge. (a) Explain the
variation in the
concentration of
ammonium ions
and dissolved
oxygen,
downstream from
point of sewage
discharge.
(i) Ammonium
ions.
(ii) Dissolved
oxygen

(b) Suggest two ways in which the effects of sewage shown on the graph can be monitored.
2. Figure below shows the effect of food content on the population growth of flour beetles of the
same species.
(a) Compare the effect of
food content on the
population growth of
flour beetles with time.
(b) Explain the effect of food
shortage on the
population growth of
flour beetles.
(c) State one density
independent factor that
would influence the
results of this
experiment.

3. The water hyacinth Eichhornia crassipes is a weed growing on many waters of Uganda. In the
biological control of the weed on Lake Victoria, a fungal pathogen and weevils are employed.
The characteristics of the fungus and the weevils in relation to their feeding behavior is shown
in the Table below.
Fungus Weevils
Feeds on the water hyacinth alone Feeds on other plants other than the water hyacinth
Attacks only the green parts of the plant Attacks all parts of the plant
The level of destruction of the weed by the fungus and the weevils under varying water
conditions in temperature, turbidity and speed of water are shown in the figures below.
 (a) From the figures above, describe the level of destruction of the weed by each of the
organisms under different conditions of water.
(i) Fungi. (ii) Weevils
(b) From the information provided, suggest explanations for the level of destruction of the
weed by each organism under different conditions of water.
(i) Fungus. (ii) Weevils
(c) From the information provided, give advantages that the;
(i) fungus has over weevils in destroying the weed.
(ii) Weevils have over fungus in destroying the weed.
(d) What are ecological effects of the water hyacinth on Lake Victoria?
(e) What are the advantages of employing biological control as a means of checking
the population of the water hyacinth?
4. (a) What is gross primary productivity?
(b) The diagram below shows the energy flow in KJm -2year-1 through a fresh water ecosystem.

Energy from the sun i) Calculate the gross

primary
productivity of the
pond weed and
48621 algae.
Pond weed and algae Respiration
ii) How much energy
is lost in
21724 respiration and
Other organisms
waste products by
the fresh water
Fresh water snails (13122) Respiration and snails?
waste products (c) Explain why
Other organisms 4210 carnivores would
have a higher
1269 secondary
Leeches (1529) Respiration and productivity than
waste products herbivores.
Other organisms 194

Stickle backs

5. The yield of bean plants was monitored against different factors in an uninterrupted field
close to a dusty road side.
Figure below shows the relationship between weed density and bean density ha-1
(a) Describe the relationship between weed density
and bean seed density
(b) Explain the relationship in (a) above
(c) Identify the biological process illustrated in the
figure above and explain its importance in nature.
(B) SECTION B TYPE QUESTIONS
1. (a) What is meant by the term population in ecology?
(b) What assumptions are made when using capture –recapture method of estimating
population size?
(c) Explain the ways in-breeding affects a natural population.
(d) Suggest factors which may contribute to a climax community being unstable.
2. (a) What is meant is meant by
(i) Biotic potential
(ii) Primary productivity
(b) Describe the factors which influence the size of population in an ecosystem.
(c) Suggest reasons why human populations are not naturally regulated by negative
feedback mechanism.
3. (a) Define the term fecundity.
(b) Describe how each of the following affect a natural population.
(i) Diseases
(ii) Predation
4. (a) Differentiate between sample count and total count.
(b) Give five factors to be considered before carrying out a counting exercise.
(c) Outline the importance of determining population size of different organisms in a given
area to an ecologist.
5. (a) Discuss the different ways in which man has influenced natural habitats to suit his life
style of living.
(b) What is the long term effects of the following
(i) Pesticide application
(ii) Global warming
(c) Explain how the release of chlorofluorocarbons (CFCs) into the atmosphere can
endanger the ecosystem.
6. (a) What is meant by the term environmental degradation?
(b) Explain the ecological impacts of each of the following human activities.
(i) Use of pesticides
(ii) Drainage of nitrate into water bodies
(iii) Use of polythene papers
(b) How can endangered species be conserved?
(c) What are the benefits of conserving nature?
7. (a) What is meant by greenhouse effect?
(b) How have humans contributed to increased greenhouse effect?
(c) Suggest practical solutions to the greenhouse problem.
8. (a) Explain the sources and types of air pollution.
(b) What are the effects of land pollution on agricultural productivity?
9. (a) Distinguish between primary productivity and secondary productivity.
(b) Give five reasons why much of the solar energy does not contribute to primary
productivity in plants.
(c) Explain why carnivores have a higher secondary productivity than herbivores.
10. (a) Describe the factors that influence productivity in an ecosystem.
(b) What are the effects of light in an ecosystem?
11. Describe
(a) how different human activities results into poor quality of air and water
(b) ecological impacts of organic pollution on fresh water bodies
12. (a) Explain the meaning of pest resurgence.
 (b) Describe the qualities of an ideal pesticide.
(c) What are the
(i) benefits of biological agents over pesticide in pest control
(ii) limitations of using Biological control.
13. (a) What is meant by the term Economic damage threshold of pests?
(b) Describe various cultural methods of controlling pest population.
(c) Explain the sequence of the changes that occur in a previously burnt piece of land from
its initial stages until a climax community.
14. (a) Distinguish between primary and secondary succession.
(b) Describe the functional changes that occur in the ecosystem during succession.
(c) Explain the adaptations of lichens as Pioneer species.
15. (a) (i) Distinguish between a food chain and a food web.
(ii) Evaluate the use of studying food webs rather than food chains in ecology
(b) Explain how energy flows through an ecosystem.
(c) How does temperature influence the distribution of organism?
(d) Explain the adaptations of plants to fire.
16. (a) How does each of the following influence plant distribution?
(i) Acidic rain
(ii) Temperature
(iii) Light
(b) Explain why apical dominance is more common in plants that grow under forest canopy
than those in open habitats.
17. (a) Describe and explain the changes in fauna, flora and chemical composition that would
occur along a fresh water river due to dumping of domestic sewage from a nearby
residential town.
(b) Describe how terrestrial plants in xeric habitats are suited to their environments.
18. (a) What is meant by
(i) species
(ii) species extinction
(b) Outline human activities that may lead to formation of new species.
(c) Explain how man has contributed to formation of new species.

END