succession

Question 1

1. Describe the term abiotic factor and give examples.

Answer 1

A non-living factor, such as pH, temperature or rainfall.

Question 2

2. Describe the term biotic factor and give examples

Answer 2

Living factors, such as predation or competition.

Question 3

3. Describe the first stage of primary succession.

Answer 3

Barren land e.g. bare rock is colonised by a pioneer species.

Question 4

4. Give the adaptations of pioneer species.

Answer 4

Production of vast quantities of wind-dispersed seeds or spores (they can reach isolated areas quickly). Rapid germination of seeds on arrival as they don’t need a period of dormancy. Ability to photosynthesis quickly (no dependence on animals) and so grow quickly. Ability to fix atmospheric nitrogen as there is no soil, or the soil is deficient in minerals. Tolerance to extreme climatic conditions.

Question 5

5. Explain what happens in succession after the pioneer species is established.

Answer 5

The pioneers change the abiotic conditions, making it less hostile and more suitable for other species with different adaptations, the next species colonises and further changes the abiotic conditions making it less hostile and more suitable for other species with different adaptations. This repeats until a climax community is established. Over time biodiversity increases due to more habitats, niches, formation of soil, humus, organic matter, increase in nutrients. Increase in diversity of species.

Question 6

6. Explain what happens to biomass in succession.

Answer 6

It increases as succession moves through the stages, then is stable during the climax community, as the rates of photosynthesis and respiration are stable.

Question 7

7. Explain what happens to biodiversity in succession.

Answer 7

At first it increases as succession moves through the stages, then it reduces during the climax community as the dominant species reduces the amount of light/nutrients available to others.

Question 8

8. Explain why succession leads to more stable communities.

Answer 8

Climax communities are stable as they have complex food webs, and are in equilibrium, allowing for changes in the environment.

Question 9

9. Describe how secondary succession is different to primary succession.

Answer 9

Secondary succession starts with soil, not barren land, and happens usually after fires. The pioneer stage is missed out.

Question 10

10. Explain why the dominant species change through succession

Answer 10

Species change as the conditions become more/less favourable. Some species are better at competing in the new conditions.