Unit 10- Succession

Question 1

What is succession?

Answer 1

When ecosystems slowly change over time

Question 2

What is a stable community called?

Answer 2

Climax community

Question 3

What are the stages of succession called?

Answer 3

Serial stages or serial communities, and the whole succession is called a sere

Question 4

How does succession begin in such harsh conditions?

Answer 4

Wind dispersed seeds called colonisers can survive in the harsh conditions by being small and fast growing with shallow roots

Question 5

Describe succession in general:

Answer 5

• wind-dispersed seeds colonise the harsh environment
• larger pioneer species with animal dispersed seeds and deep roots begin growing
• each plant changes the environment by creating deeper soil and shade
• more species can colonise in these less harsh conditions
• the new species are bigger and outcompete, replace the older species

Question 6

How does succession lead to less harmful conditions? 3 reasons

Answer 6

• daily temps don’t fluctuate as much due to shade
• water is more available as it is retained in the soil
• nitrates increase due to nitrogen fixation and decay
• as more plant communities colonise there becomes more food for primary consumers and secondary consumers

Question 7

What is the difference between primary and secondary succession???

Answer 7

Primary- starts with bare rock or sand (after a volcanic eruption)
Secondary- starts with soil (after a forest fire)

Question 8

Give 2 examples of colonisers

Answer 8

Lichen and phytoplankton

Question 9

What are the 2 types of primary succession?

Answer 9

Lithosere - from a bare rock with lichens (breaks the rock with acid)
Hydrosere- from water (phytoplankton live, die sink to the bottom to provide organic matter)

Question 10

What is a plagioclimax and how is it maintained?

Answer 10

A plagioclimax is a landscape that is held at pre-climax stages by constant human intervention
- by ploughing, weeding, herbicides, grazing animals, mowing ….

Question 11

Why does grazing stop succession at the grassland stage?

Answer 11

Broad-leafed plants (dicotyledons) have strong stems so are usually uprooted and fully killed when eaten
Narrow leaved plants (monocotyledons, grass) have weaker stems so cannot be uprooted and killed
Therefore weeds get killed and grass continues growing

Question 12

What are biomes? Give an example

Answer 12

The major different climatic climax communities in the world, eg tropical forests, dry deserts