7.2 Ecology (organisation of an ecosystem 2)

Question 1

Why are microorganisms important for the cycling of materials through an ecosystem?

Answer 1

• microorganisms (bacteria and fungi) return carbon to the environment by releasing carbon dioxide through respiration while they decompose dead matter
• the decomposition of dead matter in soil returns mineral ions to the environment for other organisms to use

Question 2

What is meant by decomposition?

Answer 2

the breakdown of dead materials into simple organic matter

Question 3

How do decomposers break down dead matter?

Answer 3

decomposers release enzymes which catalyse the breakdown of dead material into smaller molecules

Question 4

What are the two types of decomposition?

Answer 4

• aerobic decomposition (with oxygen)
• anaerobic decomposition (without oxygen)

Question 5

What factors affect the rate of decomposition?

Answer 5

• oxygen availability
• temperature
• water content

Question 6

Why is oxygen required for deomposition?

Answer 6

most decomposers require oxygen for aerobic respiration

Question 7

How does the availability of oxygen affect the rate of decomposition?

Answer 7

• as oxygen levels increase, the rate of decomposition increases
• as oxygen levels decrease, the rate of decomposition decreases

Question 8

Why can decomposition still occur in the absence of oxygen?

Answer 8

• some decomposers respire anaerobically
• however the rate of decomposition is slower as anaerobic respiration produces less energy

Question 9

How does soil water content affect the rate of decomposition?

Answer 9

decomposers require water to survive:
- in moist conditions the rate of decomposition is high
- in waterlogged soils there is little oxygen for respiration so the rate of decomposition decreases

Question 10

Why does decomposition require water?

Answer 10

water is required for the secretion of enzymes and absorption of dissolved molecules

Question 11

How does temperature affect the rate of decomposition?

Answer 11

• the optimum temperature is 50 degrees celsius
• lower temperature, enzymes work too slowly, rate decreases
• higher temperatures, enzymes denature, decomposition stops

Question 12

How is the rate of change calculated when considering the decay of biological material?

Answer 12

rate of change = change in value / change in time

Question 13

What is compost?

Answer 13

the nutrient-rich product of the rapid decay of waste biological material in optimum conditions set by gardeners and farmers

Question 14

How is compost used?

Answer 14

used as natural fertiliser to promote growth of crops or garden plants

Question 15

Describe how biogas generators work

Answer 15

biogas generators provide methane gas for fuel through anaerobic decomposition that occurs in animal waste

Question 16

Describe how environmental conditions affect communities

Answer 16

environmental conditions affect the abundance and distribution of organisms within communities

Question 17

How can different temperatures be bad for certain communities?

Answer 17

• if the temperature is too low, growth will be slower as organisms will use more energy to stay warm
• if the temperature is too high, organisms can die and water will become limited as evaporation increases

Question 18

How can changes in water levels affect ecosystems?

Answer 18

• animals may have to migrate to find water
• melting ice caps may destroy the habitats of some animals

Question 19

How can atmospheric gases affect ecosystems?

Answer 19

• some organisms cannot survive when certain gases are present
• polluted water can cause illness to animals that drink it

Question 20

How is carbon monoxide formed?

Answer 20

from the incomplete combustion of fossil fuels

Question 21

What detrimental impacts can carbon monoxide have on the environment?

Answer 21

• carbon monoxide binds irreversibly to haemoglobin which prevents it from carrying oxygen
• too much exposure can cause unconsciousness and death

Question 22

Name 5 greenhouse gases

Answer 22

• water vapour
• carbon dioxide
• nitrous oxide
• methane
• CFCs

Question 23

Give 3 human activities that contribute to greenhouse gases?

Answer 23

• deforestation
• burning fossil fuels
• large scale livestock farming

Question 24

How do greenhouse gases lead to global warming?

Answer 24

• greenhouse gases allow heat from the sun to enter the atmosphere
• the gases act as a ‘blanket’ and trap heat in the atmosphere

Question 25

State 3 negative consequences of global warming

Answer 25

• sea level rise caused by melting icebergs
• disrupted farming and agriculture
• increased spread of diseases in warmer climates