Toic 10.3 - Ecological Succession

Question 1

What is primary succession?

Answer 1

Community developing on bare, uncolonised ground
No previous life, vegetation or soil

Question 2

What is secondary succession?

Answer 2

Community colonisation ground which had been previously colonised whom have been destroyed (eg fire, flood, human activities)

Usually quicker process than primary succession

Question 3

What are 5 stages of succession? (4 marks)

Answer 3

1. Migration, colonisation by Pioneer species
2. die and decay, leaving humus, contributing organic matter to form soil
3. Creating suitable conditions for other species to establish
4. Leading to succession of a species
5. Climax community formed (end point), environment now stable

Question 4

What are seres?

Answer 4

Stages in a complete seral succession

Question 5

What’s so special about pioneer species?

Answer 5

Can withstand extreme conditions so able to colonise areas

Question 6

What are pioneer species?

Answer 6

Resilient Organisms that are first to colonize barren environments, adaptive to harsh conditions (extremophiles)
Must be producers (make their own food)

Question 7

What effect will pioneer species eventually have on the rock?

Answer 7

• eventually penetrate rock surface, break down
• start soil formation

Question 8

What are examples of pioneer species?

Answer 8

Lichens, then mosses then soils, grasses, weed, shrubs, bushes and eventually trees

Question 9

How do mosses work as pioneer species?

Answer 9

Grow and die, adding to soil to support growth of grass and weeds
Increasing nutrients in soil (aka forming Humus) for other plants to grow

Question 10

How is soil formed by pioneer species?

Answer 10

Erosion of rocks, with water and wind, forming soil
Gives opportunities for diverse plants to grow on with increasing humus and nutrients

Question 11

What is humus?

Answer 11

Dead and decaying (by microorganisms) plants and animals (& faeces)
(Nutrients broken down added to soil)

Question 12

As the environment changes (abiotic), the species that inhabit it will…

Answer 12

Also change (biotic)

Question 13

How does succession on sand dunes work? 3 steps

Answer 13

1. Pioneer species grow in sand, v v tolerant to lack of water
2. Sand accumulates around the plants, it dies and decays
3. Humus mixes with sand, forming mini sand dune, allowing bigger plants to grow

Question 14

Define succession (2 marks)

Answer 14

Sequence of changes in a species (1)
Over a period of time (1)

Question 15

What is a climax community? 2 marks

Answer 15

The final stage
Of community that are stable, self sustaining

Question 16

How does colonisation of bare rocks by lichens result in succession over long periods of time? (4 marks)

Answer 16

• they are pioneer species
• erode and break down rocks
• they die and decay, leaving humus
• provide niches for other organisms to grow in

Question 17

What is mean by ecosystem?

Answer 17

Interactions between organisms and their environment

Question 18

Explain why the efficiency of energy transfer differs between tropic levels. (3 marks)

Answer 18

• different trophic levels use different proportions of energy
• respiration for movement (heat loss)
• some materials not consumed
• some parts not digested
• released from excretion

Question 19

Give one reason why the energy transfer from sunlight to the producers is less than 100% efficient. (1 mark)

Answer 19

• light reflected / missed chloroplasts

Question 20

What is a niche?

Answer 20

environmental factors and interspecies relationships that influence the species.