Ecological succession

Question 1

What is meant by the term succession?

Answer 1

Succession is the process by which communities colonise an ecosystem and are then replaced over time by other communities.

Question 2

What types of succession are there?

Answer 2

Primary succession and secondary succession.

Question 3

What is primary succession?

Answer 3

The progressive colonisation of bare rock or other barren terrain by living organisms.

Question 4

What is secondary succession?

Answer 4

The recolonisation of an area after an early community has been destroyed.

Question 5

What is a pioneer species?

Answer 5

The first living organisms to colonise an area.

Question 6

What is a climax community?

Answer 6

The organisms present in the final stage of succession e.g. woodland.

Question 7

What is biodiversity?

Answer 7

The range and variety of living organisms within a particular area.

Question 8

What is biomass?

Answer 8

The total mass of living material in a given area at one time. Usually measured as dry mass as the amount of water can vary.

Question 9

Give 3 examples of when primary succession might occur?

Answer 9

A glacier retreat retreating and leaving rock; silt and mud being deposited at river estuaries; sand being deposited by the wind or sea.

Question 10

What types of harsh conditions may be present at the beginning of sand dune succession?

Answer 10

Salty, dry, lacking in nutrients, mobile substrate.

Question 11

What features do pioneer species have?

Answer 11

Ability to fix nitrogen, tolerance to extreme conditions e.g. xerophytes; ability to photosynthesise due to shortage of ‘food’/nutrients, waxy cuticles, long roots, salty cell sap, curled leaves
Rapid germination of seeds, production of wind dispersed seeds, wind dispersed seeds can reach isolated areas.

Question 12

What might cause secondary succession?

Answer 12

Land that has already supported life is disturbed e.g. deforestation, forest fires.

Question 13

Why is secondary succession normally quicker than primary succession?

Answer 13

Seeds may be present in the soil, plants could disperse from nearby areas, animals could migrate from nearby areas.

Question 14

How does the climax community and the new environment normally compare to the start of succession?

Answer 14

There is an increased biodiversity, there is an increased biomass, shelter from wind is present, there are more nutrients available, soil is present, there are more complex food webs.

Question 15

What are the climax communities in the UK?

Answer 15

Woodlands - oak trees.

Question 16

Why is a new community formed in succession?

Answer 16

Changes in the environment make it more suitable for other species, which may then out-compete the species in the existing community and so a new community is formed.

Question 17

What can you normally find within a climax community?

Answer 17

A dominant plant species and a dominant animal species.

Question 18

What is stopping/managing succession a method of?

Answer 18

Conservation.

Question 19

What is conservation?

Answer 19

The management of the Earth’s natural resources in such a way that maximum use of them can be made in the future. It is also looking after and maintaining rarer species.

Question 20

What are the three main reasons for conservation?

Answer 20

Ethical, economic, and social & aesthetic.

Question 21

Explain the ethical reason for conservation.

Answer 21

Other species have occupied the Earth far longer than we have and should be allowed to coexist with us. Respect for living things is preferable to disregard for them.

Question 22

Explain the economic reason for conservation.

Answer 22

Living organisms contain a large pool of genes with the capacity to make millions of substances, many of which may prove valuable in the future. Long term productivity is greater if ecosystems are maintained in their natural balanced state.

Question 23

Explain the cultural & aesthetic reason for conservation.

Answer 23

Habitats and organisms enrich our lives. Their variety adds interest to everyday life and inspires writers, poets, artists, composers and others who entertain and fulfill us.

Question 24

How would you manage succession of heather?

Answer 24

Burning, grazing, mowing.

Question 25

How would you manage succession of Wicken Fen wetland?

Answer 25

Sedge harvest and removal of biomass from the site. Brinking and slubbing of the watercourses.

Question 26

How would you manage succession of forests?

Answer 26

Coppicing and burning.

Question 27

How would you manage succession of sand dunes?

Answer 27

Grazing on areas of dense vegetation, boardwalks, fencing.

Question 28

How would you manage succession of Salisbury Plain chalk grassland?

Answer 28

Tyre tracks - fairy shrimp lay their eggs in pools/puddles and tyres disperse them around the field. Scrub is removed.

Question 29

How does managing succession help with conservation?

Answer 29

It prevents a change to the next stage of succession, meaning that rarer species in the earlier stages of succession are protected as they can only survive in those particular conditions.