B17 - Organising an Ecosystem

Question 1

Define population

Answer 1

A species that occupy the same habitat.

Question 2

Define habitat

Answer 2

The place in which an organism lives.

Question 3

Define community

Answer 3

Populations of different species interacting.

Question 4

Define ecosystem

Answer 4

The interactions between the biotic and abiotic factors in an area.

Question 5

What do food chains show?

Answer 5

Food chains show the feeding relationships of different organisms and the flow of energy between the organisms.

Question 6

Define biomass

Answer 6

The total mass of living material.

Question 7

What are trophic levels?

Answer 7

The stages in a food chain.

Question 8

What do arrows in a food chain represent?

Answer 8

The direction of biomass transfer.

Question 9

Describe a simple food chain

Answer 9

producer → primary consumer → secondary consumer → tertiary consumer.

Question 10

What is a producer?

Answer 10

An organism that makes its own food.

Question 11

What types of organisms are primary producers?

Answer 11

Photosynthetic organisms like green plants and algae that trap energy from the sun.

Question 12

What is a primary consumer?

Answer 12

An organism that feeds on producers.

Question 13

What is a secondary consumer?

Answer 13

An organism that feeds on primary consumers.

Question 14

What is a tertiary consumer?

Answer 14

An organism that feeds on secondary consumers.

Question 15

What is a predator?

Answer 15

A consumer that kills and eats other animals.

Question 16

What is prey?

Answer 16

An animal that is killed and eaten by another animal.

Question 17

Describe the pattern of predators and prey in a stable community

Answer 17

The numbers of predators and prey rise and fall in cycles.

Question 18

Why are producers the first trophic level?

Answer 18

● Producers provide all biomass for the food chain (production of glucose via photosynthesis).
● The rest of the food chain involves the transfer of this biomass.

Question 19

What piece of apparatus is used to measure the abundance and distribution of organisms in an area?

Answer 19

Quadrat

Question 20

What piece of apparatus is used to study the distribution of organisms across a gradient?

Answer 20

Belt transect

Question 21

When considering the abundance of organisms, what is meant the term “mean”?

Answer 21

The average number of organisms.

Question 22

How is the arithmetic mean calculated?

Answer 22

Sum of each number of each organism/the total number of each type of organism.

Question 23

When considering the abundance of different organisms, what is meant by the term “mode”?

Answer 23

The most populous organism

Question 24

When considering the abundance of organisms, what is meant by the term “median”?

Answer 24

The organism that represents the middle value when the numbers of each organism are arranged from lowest to highest.

Question 25

Describe how materials cycle through the living and non-living components of an ecosystem

Answer 25

● Organisms take in elements from their surroundings e.g. soil, air.
● Elements converted to complex molecules which become biomass.
● Elements transferred along food chains.
● Elements returned to environment during excretion and decomposition of dead organisms.

Question 26

Give 3 molecules which are cycled through ecosystems

Answer 26

Oxygen, carbon dioxide and water.

Question 27

Describe the carbon cycle

Answer 27

• Plants fix carbon dioxide into organic molecules during photosynthesis.
• The organic carbon-containing molecules are passed onto organisms that eat the plants.
• Carbon dioxide is released back into the atmosphere by respiration from animals and plants.
• Burning fossil fuels also releases carbon dioxide into the atmosphere.

Question 28

Why is the carbon cycle important?

Answer 28

Carbon-containing molecules such as glucose are important for living organisms to grow and provide energy for vital functions within cells.

Question 29

Describe the water cycle

Answer 29

• Water from lakes and oceans evaporates.
• The evaporated water condenses into clouds and returns to earth as precipitation.
• The water from precipitation is useful for life on land.
• The water then returns to rivers and oceans through surface runoff.

Question 30

Why is the water cycle important?

Answer 30

Living organisms require water and the water cycle provides organisms on land with a continuous supply of water.

Question 31

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

Answer 31

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 e.g. plants use mineral ions for growth.

Question 32

What is meant by decomposition?
(biology only)

Answer 32

The breakdown of dead materials into simpler organic matter

Question 33

How do decomposers break down dead matter?
(biology only)

Answer 33

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

Question 34

What are the two types of decomposition? (biology only)

Answer 34

Aerobic decomposition (with oxygen)

Anaerobic decomposition (without oxygen)

Question 35

What factors affect the rate of decomposition? (biology only)

Answer 35

● Oxygen availability
● Temperature
● Water content

Question 36

Why is oxygen required for decomposition? (biology only)

Answer 36

Most decomposers require oxygen for aerobic respiration.

Question 37

How does the availability of oxygen affect the rate of decomposition? (biology only)

Answer 37

● As oxygen levels increase, the rate of decomposition increases.
● As oxygen levels decrease, the rate of decomposition decreases.

Question 38

Why can decomposition still occur in the absence of oxygen?
(biology only)

Answer 38

Some decomposers respire anaerobically.*
*However, the rate of decomposition is slower as anaerobic respiration produces less energy.

Question 39

How does soil water content affect the rate of decomposition? (biology only)

Answer 39

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 40

Why does decomposition require water?
(biology only)

Answer 40

Water is required for the secretion of enzymes and absorption of dissolved molecules.

Question 41

How does temperature affect the rate of decomposition?
(biology only)

Answer 41

Decomposers release enzymes:
● Rate highest at 50°C (optimum temperature for enzymes).
● Lower temperatures, enzymes work too slowly, rate decreases.
● High temperatures, enzymes denature, decomposition stops.

Question 42

How is the rate of change calculated when considering the decay of biological material? (biology only)

Answer 42

Rate of change = Change in value / Change in time

Where value is a measurable variable associated with the decay of the material

Question 43

What is compost?
(biology only)

Answer 43

The nutrient-rich product of the rapid decay of waste biological material (dead plants and animal waste) in optimum conditions set by gardeners and farmers.

Question 44

How is compost used?
(biology only)

Answer 44

Used as natural fertiliser to promote growth of crops or garden plants.

Question 45

Describe how biogas generators work
(biology only)

Answer 45

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

Question 46

Describe how environmental conditions affect communities
(biology only) (higher only)

Answer 46

● Environmental conditions e.g. temperature, soil pH, light intensity affect the abundance and distribution of organisms within communities.
● e.g rising global temperatures have been linked to the extinction of frog species (their thin skin makes them more vulnerable to temperature changes).

Question 47

How can different temperatures be bad for certain communities?

Answer 47

• 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 48

How can changes in water levels affect ecosystems?
(Higher)

Answer 48

• Animals may have to migrate to find water.
• Melting ice caps may destroy the habitats of some animals (either animals living in icy regions or by sea level rise).

Question 49

How can atmospheric gases affect ecosystems?
(Higher)

Answer 49

• Some organisms cannot survive when certain gases are present.
• Polluted water can cause illness to animals that drink it.

Question 50

What detrimental impacts can sulfur dioxide have on the environment?

Answer 50

• Formed when fossil fuels containing impurities are burnt.
• Sulfur dioxide can dissolve in water to form acid rain which can erode buildings and pollute water sources.

Question 51

What detrimental impacts can carbon monoxide have on the environment?

Answer 51

• Carbon monoxide is formed from the incomplete combustion of fossil fuels.
• Carbon monoxide binds irreversibly to haemoglobin which prevents it from carrying oxygen.
• Too much exposure can cause unconsciousness and death.

Question 52

Name 5 greenhouse gases

Answer 52

• Water vapour
• Carbon dioxide
• Nitrous oxide
• Methane
• CFCs

Question 53

Give 3 human activities that contribute to greenhouse gases

Answer 53

• Burning fossil fuels
• Deforestation
• Large scale livestock farming

Question 54

How do greenhouse gases lead to global warming?

Answer 54

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

Question 55

State 3 negative consequences of global warming

Answer 55

• Sea level rise caused by melting icebergs.
• Disrupted farming and agriculture.
• Increased spread of diseases in warmer climates.