Advanced Higher Biology
Taylor High School
Unit 2 – Environmental Biology
Section 2 – Interactions in ecosystems
Homework 1 – Biotic interactions
1. Outline the main examples of biotic interactions within an ecosystem.
2. Outline the main abiotic interactions within an ecosystem.
3. What are the possible factors which can upset the stable, cyclical balance
between predator and prey populations?
4. Briefly explain the ‘time lag’ that exists between predator / prey population
cycles.
5. Prey have evolved may methods of defence against predation. Outline two
methods of using camouflage as a deterrent and give named examples.
6. Outline the two lines of aposematic coloration which prey have adopted to evade
predation.
7. Ordinarily, plant communites will evolve from pioneer organisms through a
succession of communities to the climax community. Explain how ‘grazing’ can
interrupt this succession.
8. Explain the relationship between pressure of grazing and species diversity - give
an example to illustrate your answer.
Advanced Higher Biology
Taylor High School
9. Summarise the meaning of an organisms niche by reference to the physical,
chemical, biological, spatial (space) and temporal (time) factors that the organism
needs to survive.
10. Outline the differences between fundamental and realised niches.
11. What is meant by the terms:
a. exploitation competition
b. interference competition
c. interspecific competition
d. intraspecific competition
12. What is meant by the term exotic species? Give two examples each of plant and
animal exotic species and explain briefly why they are successful.
13. Explain why species diversity in an ecosystem is important for survival.
14. Explain the importance of the survival of weaker competitors in an ecosystem.
Advanced Higher Biology
Taylor High School
Unit 2 – Environmental Biology
Section 2 – Interactions in ecosystems
Homework 2 – Symbiotic interactions (Parasitism)
1. Define the general term ‘symbiotic relationship’ in terms of nutritional advantage.
2. Use named examples to distinguish between endo / ectoparasites.
3. A balance between what has co-evolved in a parasitic relationship between the
parsite and the host.
4. In terms of ‘damage to the host’ outline the difference between obligate and
facultative parasites.
5. Using named examples outline the three ways by which parasites can be
transmitted to new hosts.
6. With respect to ‘Sehistosoma’ (human blood fluke) outline the cycle of infection
involving both primary and secondary hosts.
7. Briefly outline the evolutionary process resulting in the species – specific
relationship between host / parasite.
Advanced Higher Biology
Taylor High School
Unit 2 – Environmental Biology
Section 2 – Interactions in ecosystems
Homework 3 – Symbiotic interactions (Commensalism and Mutualism)
1. Define commensalism in relation to the commencal and its ‘partner’.
2. On what basis does a commencalistic relationship usually exist? Give a named
example.
3. Define mutualism in terms of the two organisms involved.
4. Outline mutualism in terms of what co-evolution has brought about i.e. what
characteristics are there to mutualistic relationships.
5. Briefly describe mutualistic relationships which involve:
a. a micro-organism / plant
b. two vertebrates
6. In terms of benefit (+) and detriment (-), state what relationship / interaction
(and result on population density) the following interactions have:

Mutualism

Parasitism

Predation

Competition

Commensalism
7. Explain how host health can change the balance in a symbiotic relationship.
Advanced Higher Biology
Taylor High School
8. Give an example of how environmental factors can alter the balance in a symbiotic
relationship.
9. Humans manage symbiotic relationships / ecological interactions in many ways to
promote the health of human, animal and plant populations. Briefly outline some
examples of these.
Advanced Higher Biology
Taylor High School
Unit 2 – Environmental Biology
Section 2 – Interactions in ecosystems
Homework 4 – The cost, benefit and consequences of interactions
1. What are the two major types of organism response to variations in environmental
conditions? Define each.
2. Outline the implications for habitat occupation for these 2 types of organism.
3. With specific reference to osmotic and temperature variations, explain the
following terms
a. osmoconformers
b. poikilotherms
c. osmoregulators
d. homeotherms
4. Distinguish between tolerance and resistance.
5. State the function of dormancy and outline the variety of forms it can take.
6. Distinguish between ‘predictive’ and ‘consequential’ dormancy.