Energy flow through the ecosystem

Question 1

What are producers?

Answer 1

Green plants and trap solar energy and manufacture sugars from simple raw materials by photosynthesis

Question 2

What is the sun’s energy passed from?

Answer 2

One trophic level to another

Question 3

What are herbivores?

Answer 3

Primary consumers - animals that feed on plants

Question 4

What are carnivores?

Answer 4

Animals that deed on other animals

Question 5

What do both herbivores and carnivores form?

Answer 5

A feeding or trophic level with energy passing from each level to a higher one when materials are eaten

Question 6

What does energy leave the system as?

Answer 6

Heat

Question 7

What is energy lost as at every level?

Answer 7

Respiration, and through excretion of waste products

Question 8

What limits the length of the food chain?

Answer 8

The loss of energy at each level so usually limited to 4 or 5

Question 9

What is the route which energy passes between trophic levels?

Answer 9

The sequence from plant to herbivore to carnivore food chain

Question 10

What are detritivores?

Answer 10

Organisms such as earthworms which feed on small fragments of organic debris called detritus made up of non-living organic material such as fallen leaves and the remains of dead organisms.

Question 11

What are decomposers?

Answer 11

Microbes such as bacteria and fungi that obtain nutrients from dead organisms and faeces. They complete the process of decomposition started by detritivores.

Question 12

Where does the energy from one organism to another in the food chain originate from?

Answer 12

Sunlight

Question 13

What does photosynthetic efficiency (PE) indicate?

Answer 13

The ability of a plant to trap light energy

Question 14

What’s the equation for photosynthetic efficiency (PE)?

Answer 14

Quantity of energy falling on the plant

Question 15

What is Gross primary productivity (GPP)?

Answer 15

The rate at which products such as glucose are formed (mostly used up in respiration by plant)

Question 16

What is the GPP equation?

Answer 16

GPP - respiration = Net production

Question 17

What is Net primary productivity (NPP)?

Answer 17

This represents the food available to primary consumers. In crop plants it represents the yield which may be harvested.

Question 18

How do you work out NPP?

Answer 18

What is left after respiration.

Question 19

What is secondary productivity?

Answer 19

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

Question 20

How can the energy transfer be calculated between each trophic level?

Answer 20

Energy available after transfer
———————————————– x 100
Energy available before transfer

Question 21

Do herbivores or carnivores have a lower secondary productivity?

Answer 21

Herbivores have a lower one than carnivores as carnivores are more efficient at energy conversion than herbivores because they have a protein-rich diet is more readily and efficiently digested. 20% of energy is lost in the faeces of carnivores whereas 60% is lost in herbivores.

Question 22

Why are herbivores not able to eat all vegetation available to them?

Answer 22

Can’t eat roots or woody parts of grass and they are unable to digest cellulose without the aid of bacteria so pass out of body as faeces containing high proportion of undigested matter.

Question 23

What is the most accurate way of representing feeding relationships in a community?

Answer 23

Pyramid of energy which provides a quantitative account of the feeding relationships in a community.

Question 24

What does the pyramid of energy show?

Answer 24

The quantity of energy transferred from one trophic level to the next per unit area or volume per unit time. This represents the total energy requirement of each successive trophic level in a food chain.

Question 25

Why are pyramids of energy never inverted?

Answer 25

Because as material is passed up through the food chain energy is always lost through respiration as heat and in excretion so size of bars always increase sharply.

Question 26

What is primary succession?

Answer 26

The introduction of plants/animals into areas that have not previously supported a community e.g. bare rock pr site of volcanic eruption

Question 27

What is secondary succession?

Answer 27

The reintroduction of organisms into a bare habitat previously occupied by plants and animals. If the original vegetation is removed e.g. by fire or by tree felling, the area rapidly become re-colonised by a succession of different plants and animals

Question 28

What is known as a climax community?

Answer 28

A stable environment where there is no further change.

Question 29

How is bare rock colonised?

Answer 29

1) The first organisms to colonise the bare rock are algae and lichens called pioneer species and form a pioneer community.
2) This together with the weathering of the rock and the accumulation of dead and decomposing organic materials leads to the formation of primitive soil.
3) Wind-blown spores allow mosses to appear and as the soil develops grasses become established
4) As the soil builds up feep-rooted shrubs appear.
5) Over a very long time trees such as oak become established. This is known as climax community.

Question 30

What happens in secondary succession?

Answer 30

Seeds, spores and organs of vegetative reproduction ,ay remain in the soil and dispersal of plants and migration of animals will assist in colonisation of the habitat .

Question 31

How can human interference affect succession and natural development of climax community?

Answer 31

1) Grazing by sheep
2) Farming of land
3) Deforestation and soil erosion

Question 32

Why are heather moors managed and how?

Answer 32

To provide ideal conditions for game birds such as the red grouse. This is because adult grouse feed mainly on young succulent heather shoots but because heather goes through cycle of pioneer then building then mature and then degenerative they are burned every 12 years. This is due to the pioneer phase supplying the best food for adult grouse and then building stage provides best shelter for nesting so without management the heather would pass the mature to the degenerate phase and conditions would become unsuitable for the breeding of grouse.