10.1 2 How ecosystems evolve

Question 1

Succession

Answer 1

The process by which the communities of organisms colonising an area change over time

Question 2

Primary succession starts

Answer 2

With an empty inorganic surface such as bare rock or sand dune

Question 3

When is primary succession seen

Answer 3

After a volcanic eruption or landslide or the emergence of a new volcanic island

Question 4

First organisms in primary succession

Answer 4

Opportunists or pioneer species such as algae mosses and fungi
These organisms can penetrate rock surface

Question 5

First step in primary succession

Answer 5

Organisms break rock surface into grains and trap organic material will break it down to form humus
The inorganic rock grains and organic humus are the start of the formation of soil

Question 6

Once there is soil (primary succession )

Answer 6

Other species such as grasses and ferns can establish root systems . The action of their roots and humus they form when they die and decay adding to the soil

Question 7

Primary succession as the soil layer develops

Answer 7

More water and nutrients are retained and become available for plant roots so more species can survive

Question 8

Primary succession

Answer 8

Gradually larger plants develops and can be supported and the diversity of species increases

Question 9

Eventually primary succession

Answer 9

Climax community is reached

Question 10

Climax community

Answer 10

Self-sustaining community with a relatively constant biodiversity and species range . It is the most productive group of organisms that a given environment can support long term

Question 11

Climatic climax community

Answer 11

The only climax community possible in a given climate

Question 12

Plagioclimax

Answer 12

Climax community that is at least part the result of human intervention

Question 13

Secondary succession

Answer 13

The development of an ecosystem from exciting soil that is clear of vegetation

Question 14

When does secondary succession occur

Answer 14

River shift their courses , after fires and floods and after disturbances caused by humans

Question 15

Secondary succession because soil is already formed

Answer 15

Soil is already formed contains seeds roots and soil organisms the number of plants and animals present right from the beginning is much higher

Question 16

Secondary succession sequence

Answer 16

Bare earth ,grass weeds 
Grass stage
Grass and shrubs 
Young forest - pines some young hardwoods 
Mature forest - mainly oak

Question 17

Time taken to reach climax community

Answer 17

Varies
Temperature rainfall and underlying soil fertility all factors
Plants animals and microorganisms

Question 18

Important

Answer 18

Secondary climax community can differ from orginal primary climax community