Succession

Question 1

succession

Answer 1

the change in structure and composition of species in a community over time

Question 2

what is the pioneer species?

Answer 2

first plants to grow in a habitat -> often highly adapted to extreme weather

Question 3

primary succession

Answer 3

occurs in a habitat that has never before been colonised bare rock

Question 4

grassland community

Answer 4

decomposing mass and lichen establishes soil sufficient for roots of low growing herbaceous plants and grasses
seeds blown by wind into habitat established grassland

Question 5

shrubs

Answer 5

perennial woody plants outcompete grass & block sunlight - grow throughout the year - stop grasses growing underneath

Question 6

climax community

Answer 6

final stable community in an ecosystem
- dominated by trees
- wide variety of plants and animals
- growing at a variety of heights within the ecosystem

Question 7

what are the changes over time that occur throughout succession

Answer 7

• soil becomes deeper humus & mineral content increases (nitrates & phosphates)
• number of woody plants increases
• organisms living at a greater range of vertical levels
• biodiversity & stability increases
• pioneer plants are usually lost -> space becomes occupied by perennials
• many seral stage plants remain as understory plants

Question 8

explain why the climax community may have a lower biodiversity than the stage before it

Answer 8

as tall trees dominate block light from reaching lower levels of the forest - lower plants and shrubs are outcompeted by the trees

Question 9

pioneer plants are of xerophytes that can fix nitrogen

Answer 9

• as there is no existing soil to obtain nitrogen
• plants must fix nitrogen from the air
• survive in conditions with low nitrogen

Question 10

secondary succession

Answer 10

repopulation of an area that had been previously colonised, due to the habitat being disturbed or damaged

Question 11

why is secondary succession much quicker than primary succession

Answer 11

• soil already contains nitrates and phosphates -> modified by previous organisms
• already existing seed bank
• roots undisturbed in soil

Question 12

what is each sere categorised by?

Answer 12

a particular dominant species

Question 13

what is the pioneer species

Answer 13

lichens arrive on top of the rock as spores. Lichens erode the rock and as they decompose a little soil builds up

Question 14

what happens as succession progresses

Answer 14

• soil gets deeper
• nitrates and phosphates increases
• each stage of succession makes conditions more favourable for the next stage
• As more plants of different types become established and of differing heights and growth forms, there are more habitats, food sources and more niches

Question 15

deflected succession

Answer 15

where a subclimax community is maintained usually by human interference (in some cases conservation can deflect succession)