7C - Succession

Question 1

What is succession?

Answer 1

The process of ecosystem change over time.

Question 2

When do the biotic conditions of an ecosystem change?

Answer 2

As the abiotic conditions change.

Question 3

What are the 2 types of succession?

Answer 3

Primary and secondary.

Question 4

What is primary succession?

Answer 4

Happens on land that’s been newly formed or exposed - there’s no soil or organic material to start with.

Question 5

What is secondary succession?

Answer 5

Happens on land that’s been cleared of all the plants, but where the soil remains.

Question 6

When does primary succession start?

Answer 6

When species colonise a new land surface.

Question 7

Explain primary succession

Answer 7

Primary succession starts when species colonise a new land surface. Seeds and spores are blown in by the wind and begin to grow. The first species to colonise the area are called pioneer species.

• The abiotic conditions are hostile so only pioneer species grow because they’re adapted to cope with the harsh conditions.
• The pioneer species change the abiotic conditions - they die and microorganisms decompose the dead organic material (humus). The forms basic soil.
• This makes conditions less hostile , e.g. the basic soil helps to retain water, which means new organisms with different adaptations can move in and grow. These then die and are decomposed, adding more organic material, making the soil deeper and richer in minerals. This means larger plants like shrubs can start to grow in the deeper soil, which retains even more water.
• Some species may change the environment so that it becomes less suitable for the previous species.

Question 8

What is a pioneer species?

Answer 8

The first species to colonise the area.

Question 9

What is the first species to colonise the area called?

Answer 9

Pioneer species.

Question 10

Why at first during primary succession do only pioneer species grow?

Answer 10

Because they’re adapted to cope with the harsh conditions.

Question 11

What does the pioneer species do to the environment?

Answer 11

The pioneer species change the abiotic conditions - they die and microorganisms decompose the dead organic material (humus). The forms basic soil.

This makes conditions less hostile.

Question 12

How does secondary succession work?

Answer 12

In the same way as primary succession but because there’s already a soil layer succession starts at a later stage - the pioneer species in secondary succession are larger plants, e.g. shrubs.

Question 13

What happens at each stage of succession?

Answer 13

Different plants and animals that are better adapted for the improved conditions move in, out-compete the plants and animals that are already there, and become the dominant species in the ecosystem.

Question 14

What happens to the ecosystem as succession goes on?

Answer 14

It becomes more complex.

Question 15

Why does the ecosystem become more complex as succession goes on?

Answer 15

Because new species move in alongside existing species, which means that biodiversity (the variety of living organisms) increases.

Question 16

What is biodiversity?

Answer 16

The variety of living organisms in an ecosystem.

Question 17

What is the final stage of succession?

Answer 17

The climax community - the ecosystem is supporting the largest and most complex community of plants and animals it can. It won’t change much more - it’s in a steady state.

Question 18

What is a climax community?

Answer 18

The final stage of succession where the ecosystem is supporting the largest and most complex community of plants and animals it can. It won’t change much more - it’s in a steady state.

Question 19

What state is the climax community in?

Answer 19

A steady state - it won’t change much more.

Question 20

Give an example of primary succession

Answer 20

Bare rock to woodland:

1) Pioneer species colonise rocks. E.g. lichens grow on and break down rocks, releasing minerals.
2) The lichens die and are decomposed helping to form a thin soil, which thickens as more organic material is formed. This means other species such as mosses can grow.
3) Larger plants that need more water can move in as the soil deepens, e.g. grasses and small flowering plants. The soil continues to deepen as the larger plants die and are decomposed.
4) Shrubs, ferns and small trees begin to grow, out-competing the grasses and smaller plants to become the dominant species. Diversity increases.
5) Finally, the soil is deep and rich enough in nutrients to support large trees. These become the dominant species, and the climax community is formed.

Question 21

What species make up the climax community depends on what?

Answer 21

What the climate is like in an ecosystem.

Question 22

What will the climax community be like in a temperate climate?

Answer 22

There’s plenty of available water, mild temperatures and not much change between the seasons. The climatic climax will contain large trees because they can grow in these conditions once deep soils have developed.

Question 23

What will the climax community be like in a polar climate?

Answer 23

There’s not much available water, temperatures are low and there are massive changes between the seasons. Large trees won’t ever be able to grow in these conditions, so the climatic climax contains only herbs or shrubs, but it’s still the climax community.

Question 24

What does conservation often involve?

Answer 24

Managing/preventing succession in order to preserve an ecosystem in its current stage of succession.

Question 25

What is a way of managing succession?

Answer 25

Conservation.

Question 26

What can prevent succession and what does this stop?

Answer 26

Human activities, stopping a climax community from developing.

Question 27

What is the climax community called when succession is stopped artificially?

Answer 27

A plagioclimax.

Question 28

What is a plagioclimax?

Answer 28

What the climax community is called when succession is stopped artificially.