Ecology

Question 1

Define ecosystem.

Answer 1

A region in the world with similar biotic and abiotic features.

Question 2

What are biotic features?

Answer 2

All species with specialised adaptions for life in one particular ecosystem.

Question 3

What are abiotic features?

Answer 3

The physical characteristics of an ecosystem which control the biotic features. i.e climatic features and Edaphic features (soil factors such as pH)

Question 4

What is a habitat?

Answer 4

This is a subset of an ecosystem with its own specific abiotic and biotic features. e.g in a forest you have the leaf litter on the ground and the canopy.

Question 5

What is a microhabitat?

Answer 5

A subset of a habitat e.g the two sides of a leaf.

Question 6

What is a community?

Answer 6

This is a self sustaining group of different plant and animal species living in a habitat at the same time.

N.B self-sustaining means that the biomass of the producers is sufficient to support the community indefinitely.

Question 7

What is a population?

Answer 7

A group of individuals of the same species living in the same habitat at the same time.

Question 8

What is a species?

Answer 8

Any group of individuals that is capable of interbreeding to produce fertile offspring.

Question 9

What is an ecological niche

Answer 9

The role played by a species in an ecosystem or habitat

Question 10

What is the biosphere?

Answer 10

This is the totality of all ecosystems on earth.

Question 11

What is the source of energy for almost all ecosystems on earth?

Answer 11

The sun.

Question 12

What are trophic levels?

Answer 12

These are feeding levels in a food chain

Question 13

What does the first trophic level consist of?

Answer 13

The producers (autotrophs)

Question 14

What does the second trophic level consist of?

Answer 14

Primary consumers (herbivores)

Question 15

What does the third trophic level consist of?

Answer 15

Secondary consumers (carnivores)

Question 16

What does the fourth and greater trophic level consist of?

Answer 16

4th Tertiary consumers (also carnivores)
5th Quaternary consumers (carnivores)
… and so on.

Question 17

Why are there rarely more than five or six links in an ecosystem?

Answer 17

Because by this time the energy has usually run out.

Question 18

Where are the longest food chains found?

Answer 18

These exist in regions of the world where primary production by plants is at its maximum.

Question 19

Why does energy rapidly run out in food chains?

Answer 19

There are many reasons for this. Two of the main ones are that only a tiny percentage of the solar energy hitting the earth actually ends up in plants and that the energy transfer between each trophic level is very low.

Other reasons include energy lost as heat in respiration and that much of the energy in the producers is not available to herbivores i.e dead leaves are consumed by detrivores and much of the energy is contained in the roots

Question 20

What is gross production/productivity?

Answer 20

This is the total organic production by plants

Question 21

What is Net production?

Answer 21

This is the amount of the gross production available to the next feeding level i.e net production = Gross production - energy used up in respiration.

Question 22

Why is net production much smaller at the next level of the food chain i.e primary consumer to secondary consumer?

Answer 22

Because animals use up much more of their energy than plants do. Further more as animals are heterotrophic lots of energy is lost in non-digested food i.e is lost through egestion.

Question 23

Define succession.

Answer 23

The change in structure in a community over time due to changes in environmental factors.

Question 24

What are the two types of succession?

Answer 24

Primary succession

Secondary succession

Question 25

What is primary succession?

Answer 25

the sequence or arrival of plants and animals in a newly available habitat which changes bare rock eventually to woodland.

Question 26

What is secondary succession?

Answer 26

The re-colonization of a pre-existing habitat. e.g following a forest fire.

Question 27

Outline the process of primary succession.

Answer 27

1. ) Weathering processes convert bare rock to mineral particles.
2. ) Lichens and mosses colonize the shallow mineral soil
3. ) As these die and rot down the organic content begins to build up and the soil is able to support larger plants like ferns.
4. ) Small animals like insects worms and mice move in because gross productivity is enough to support them.
5. ) The soil gets progressively deeper and small shrubs begin to move in; at which point birds and large mammals begin to arrive.
6. ) Eventually the soil becomes rich enough to support the growth of trees

Question 28

What brings an end to the process of succession?

Answer 28

The establishment of a climax community.

Question 29

What is secondary productivity?

Answer 29

The rate at which consumers accumulate energy in the form of cells or tissues.

Question 30

What is a climax community?

Answer 30

A stable community with no further succession.

Question 31

How is secondary succession different to primary succession?

Answer 31

This is much faster than primary succession because the soil already exists.

Question 32

Give an example of secondary succession.

Answer 32

When a tree falls in a forest, the space is rapidly occupied by an opportunistic species i.e weeds. These plants have to grow rapidly because in one or two years new trees will have filled the gap using their seeds as a means of dispersal.