23.4 Succession

Question 1

Succession

Answer 1

Process by which ecosystems change over time

Question 2

2 types of succession

Answer 2

Primary

Secondary

Question 3

Primary succession

Answer 3

Occurs on newly formed land or bare rock

No soil or organic material to begin with

Question 4

Secondary succession

Answer 4

Occurs where soil is present but with no plant or animal species
Eg bare Earth after forest fires

Question 5

When does primary succession occur?

Answer 5

Volcanoes erupt, releasing lava that forms igneous rock
Sand blown by the wind to form dunes
Silt and mud deposited at river estuaries
Glaciers retreat, depositing rubble and exposing rock

Question 6

Seral stage

Answer 6

A step in the process of succession

At each stage, there is a change in abiotic factors (especially the soil)

Question 7

Main seral stages

Answer 7

Pioneer community
Intermediate community
Climax community

Question 8

Which is faster - primary or secondary succession?

Answer 8

Secondary succession

Question 9

Pioneer community

Answer 9

Pioneer species arrive as spores or seeds carried by the wind by droppings of birds or animals

Question 10

Adaptations of pioneer species

Answer 10

Can produce a large amount of spores and seeds
Seeds germinate rapidly
Can photosynthesise to produce their own energy
Can tolerate extreme environments
Can fix nitrogen from the atmosphere

Question 11

Intermediate community

Answer 11

Weathering of bare rock produces particles that form the basis of soil
When pioneer species decompose, humus is formed
Soil can now support growth of new organisms

Question 12

Eg of pioneer species

Answer 12

Lichen

Question 13

Eg of secondary colonisers

Answer 13

Mosses

Question 14

Eg of tertiary colonisers

Answer 14

Ferns

Question 15

Adaptations of tertiary colonisers

Answer 15

Waxy cuticle to prevent against water loss

Can survive without abundance of water but absorb nutrients from soil

Question 16

Climax community

Answer 16

Final seral stage

Community is in a stable state and shows very little change over time

Question 17

Biodiversity in a climax community

Answer 17

Not usually the most diverse
Highest diversity in mid succession
Biodiversity decreases due to dominant species outcompeting pioneer and other species, causing elimination

Question 18

Animal succession

Answer 18

Primary consumers (worms, insects) first colonise an area 
Secondary consumers arrive once a suitable food source has been established and existing plant cover provides suitable habitats

Question 19

Which is faster - animal or plant succession?

Answer 19

Plant

Animal succession takes longer, especially land is geographically isolated

Question 20

Plagioclimax

Answer 20

When succession is stopped artificially, the final stage formed

Question 21

Ways of halting succession

Answer 21

Grazing and trampling of vegetation by domesticated animals - areas remain as grassland
Removing existing vegetation to plant crops - crops become final community
Burning to clear forest - increase biodiversity due to ash