Changes in ecosystems

Question 1

Ecological succession

Answer 1

Primary succession
Hydrosere
Lithosere
Secondary succession
Plagioclimax

Question 2

Primary succession

Answer 2

The sequence of changes in community composition in an area
Starts with colonisation for the first time
Continues until climax community
Species that colonise change the abiotic factors
new abiotic conditions lead to new colonisers
New colonisers outcompete old colonisers
new species can survive because of better conditions or presence of new species

Question 3

Sequence of changing communities

Answer 3

Sere

Question 4

Climax community

Answer 4

Usually controlled by climate

Climatic climax

Question 5

Hydrosere

Answer 5

A succession process beginning in water
Freshwater and saltwater hydroseres
Freshwater begins with with single celled algae from the soil
Emergent plans outcompete submergent for sunlight
As plants grow and die, lakes get filled in
Aquatic species die out as willows and alder colonise the new soil
Soils dry out and more trees colonise
Climax community contains no species involed in earlier stages

Question 6

Lithosere

Answer 6

Succession process beginning on bare rock
Early abiotic conditions are harsh
There is no soil, extreme of temperatures, and low water availability
Pioneer species are simple autotrophs like lichens
Regolith and dead organic matter build up
Mosses colonise
Thin layer of soil forms
Grasses and ferns colonise
Abiotic factors get less extreme as more, larger plants colonise
Insects arrive
Edaphic features become suitable so trees can colonise
Climax community is very similar to hydrosere

Question 7

Secondary succession

Answer 7

Changes that occur in an area that has already reached climax state
Natural events eg. forest fires, hurricanes as well as human activities eg. deforestation, grazing interrupt succession
The climax community can be removed
Succession will begin again but quicker than primary succession
Quicker since seeds and soil are already present

Question 8

Plagioclimax

Answer 8

Human activities which destroy the climax community an then continue
A new community will develop
Often unable to tell the community is maintained by human activities
Natural succession process is prevented
Necessary in UK to protect some species
Eg. hazel dormouse