Biological Pyramids and Succession

Question 1

What does the Pyramid of Numbers show?

Answer 1

The number of individuals at each level

Question 2

What are the restrictions of a Pyramid of Numbers?

Answer 2

.It doesn’t take into account the size of organisms
.It does not recognise the difference between adult and juvenile forms
.Numbers can be difficult to draw to scale
.The pyramid may be inverted

Question 3

What does the Pyramid of Biomass show?

Answer 3

Is a measure of the total dry mass of organisms in a given area?

Question 4

What are the restrictions of a Pyramid of Biomass?

Answer 4

.Difficult to measure accurately
.They don’t indicate productivity or the amount of energy flowing through the ecosystem
.They can be inverted
.Species with same biomass may have different life span
.Certain structures (bones, beak, etc.) don’t contribute any biomass to the next trophic level.

Question 5

What are the advantages of a Pyramid of energy?

Answer 5

.Accurate at representing feeding relationships
.Shows available energy
.In Kj hectare-1 year-1
.Shows the efficiency of energy transfer between trophic levels in different communities.
.Never inverted to easy to compare

Question 6

Define Succession

Answer 6

The gradual change in structure and species composition of a community over time.

Question 7

How does succession start?

Answer 7

It starts with pioneer species which live in low fertility and can often fix nitrogen

Question 8

What is a sere?

Answer 8

The sequence of communities, with the different species and structures.

Question 9

What is a seral stage?

Answer 9

The different stages of succession when particular communities dominate

Question 10

What happens until a climax community is established?

Answer 10

New species invade and replace existing ones

Question 11

When is a climax community established?

Answer 11

When a change in environmental factors or abiotic factors occurs

Question 12

Define Primary coloniser or pioneer plant

Answer 12

There are the first plants to grow in a new habitiat

Question 13

Define Climax Community

Answer 13

The final collection of plants and animals that succession produces. A community that has reached equilibrium with its environment and no further changes occur

Question 14

Define Primary Succession

Answer 14

Colonization of living organisms into an area that has not been colonised before

Question 15

Define secondary succession

Answer 15

Re-colonization / reintroduction of organisms into a bare habitat that was previously occupied by plants and animals.

Question 16

How do you think soil depth will change as succession proceeds?

Answer 16

increases as plants die

Question 17

How do you think soil water content will change as succession proceeds?

Answer 17

increases due to deeper soil

Question 18

How do you think soil fertility will change as succession proceeds?

Answer 18

Increases due to deeper soil

Question 19

How do you think biomass of plants per metre will change as succession proceeds?

Answer 19

Increases as water and fertility increased

Question 20

How do you think biodiversity per unit area will change as succession proceeds?

Answer 20

Increases as more niches are available

Question 21

What happens to soil during succession?

Answer 21

Becomes deeper and the humus and mineral nutrient content goes up

Question 22

What happens to primary production during succession?

Answer 22

Increases

Question 23

What happens to biodiversity during succession?

Answer 23

Increases

Question 24

What happens to the height and biomass of the vegetation during succession?

Answer 24

Increases

Question 25

What happens to the number of food chains during succession?

Answer 25

Increases

Question 26

What happens to the number of woody plants during succession?

Answer 26

Increases

Question 27

What four factors have equilibrium in a climax community?

Answer 27

1. GPP= Total respiration
2. Energy used from sunlight = energy released by decomposition
3. Uptake of nutrients from the soil = Their recycling
4. New Growth and Decomposition

Question 28

Define Disclimax

Answer 28

This is when the succession does not proceed through to the climax community.

Question 29

What causes Disclimax?

Answer 29

1. Poor soil may prevent trees growing (edaphic climax)

2. Human intervention may also divert the climax resulting in a plagioclimax

Question 30

Define Secondary Succesion

Answer 30

Secondary succession is the series of community changes which take place on previously colonized, but disturbed or damaged habitat.

Question 31

Why is secondary succession much quicker than primary succession?

Answer 31

1. There is already an existing seed bank of suitable plants in the soil
2. Root systems undistributed in the soil, stumps and other plant parts from previously existing plants can rapidly regenerate.
3. The fertility and structure of the soil has also already been substantially modified by previous organisms to make it more suitable for growth and colonization.

Question 32

What factors affect succession?

Answer 32

1. Migration
2. Competition
3. Facilitation

Question 33

Define Mutualism

Answer 33

Is an interaction between species that is beneficial to both

Question 34

Define Commensalism

Answer 34

An interaction between two species in which one benefits and the other is unaffected.