19) Ecology (4.5)

Question 1

1.1. What is the principal source of energy input to biological systems?

Answer 1

The Sun

Question 2

1.2. Describe the flow of energy through living
organisms

Answer 2

Light energy from the Sun flows to the first trophic level

Producers convert it to chemical energy, which flows from one consumer to the next

Eventually all energy is transferred to the environment; some energy is used and lost at each stage

Non-cyclical process; once energy gets to the top of the food chain/web, it is not recycled but “lost” to the environment

Question 3

2.1 Describe a food chain

Answer 3

It shows the transfer of energy from one organism to the next, beginning with a producer

Question 4

2.3 Describe a food web

Answer 4

A network of interconnected food chains and interpret food webs

Question 5

2.4 Describe a producer

Answer 5

An organism that makes its own organic nutrients, usually using energy from sunlight, through photosynthesis

Question 6

2.5 Describe a consumer

Answer 6

An organism that gets its energy by feeding on other organisms

Question 7

2.6. How may consumers be classed according to their position in the food chain?

Answer 7

Primary, secondary, tertiary and quaternary

Question 8

2.7. Describe a herbivore

Answer 8

An animal that gets its energy by eating plants

Question 9

2.8. Describe a carnivore

Answer 9

An animal that gets its energy by eating other animals

Question 10

2.9. Describe a decomposer

Answer 10

An organism that gets its energy from dead or waste organic material

Question 11

2.12 Discuss the advantages of using a pyramid of biomass rather than a pyramid of numbers to represent a food chain

Question 12

2.13. Describe a trophic level

Answer 12

The position of an organism in a food chain, food web or ecological pyramid

Question 13

2.16. Discuss the advantages of using a pyramid of energy rather than pyramids of numbers or biomass to represent a food chain

Question 14

2.17. Explain why the transfer of energy from one trophic level to another is often not efficient

Question 15

2.18. Explain, in terms of energy loss, why food chains usually have fewer than five trophic levels

Question 16

2.19. Explain why it is more energy efficient for humans to eat crop plants than to eat livestock that have been fed on crop plants

Question 17

3.1. Describe the carbon cycle

Answer 17

Photosynthesis:
Respiration:
Feeding:
Decomposition:
Formation of fossil fuels:
Combustion:

Question 18

3.2. Describe the nitrogen cycle

Answer 18

Decomposition of plant and animal protein to
ammonium ions:

Nitrification:

Nitrogen fixation by lightning and bacteria:

Absorption of nitrate ions by plants:

Production of amino acids and proteins:

Feeding and digestion of proteins:

Deamination:

Denitrification:

Question 19

3.3. State the roles of microorganisms in the nitrogen cycle

Answer 19

Decomposition:
Nitrification:
Nitrogen fixation:
Denitrification:

Question 20

4.1. Describe a population

Answer 20

A group of organisms of one species, living in the same area, at the same time

Question 21

4.2. Describe a community

Answer 21

All of the populations of different species in an ecosystem

Question 22

4.3. Describe an ecosystem

Answer 22

A unit containing the community of organisms and their environment, interacting together

Question 23

4.4. Identify and state the factors affecting the rate of population growth for a population of an organism

Answer 23

Food supply
Competition
Predation
Disease

Question 24

4.5. Identify the lag, exponential (log), stationary and death phases in the sigmoid curve of population growth for a population growing in an environment with limited resources

Question 25

4.7 Explain the factors that lead to each phase in the sigmoid curve of population growth, making reference, where appropriate, to the role of limiting factors

Answer 25

Lag: organisms adapt to the environment before they are able to reproduce. There are few organisms so reproduction is not producing larger numbers of offspring

Log (exponential): food supply is abundant, birth rate is rapid, death rate is low. Growth is exponential and only limited by the number of new individuals that can be produced

Stationary: population levels out due to a factor, such as a nutrient, becoming limited as it is not being replenished. Birth and death rates are equal until the nutrient is replenished or severely limited

Death: population decreases as death rate is now greater than birth rate, usually because food supply is short or metabolic wastes produced have built up to toxic levels