Organisation of an ecosystem (7.2) (M)

Question 1

What is the role of photosynthetic organisms on Earth?

Answer 1

the producers of biomass for life on Earth

Question 2

Feeding relationships within a community can be represented by what?

Answer 2

food chains

Question 3

What do food chains always begin with?

Answer 3

a producer which synthesises molecules

Question 4

2 needed

What organisms are commonly producers? How do they contribute to the food chain?

Answer 4

green plant or alga

they make glucose by photosynthesis

Question 5

Techniques such as quadrats and transects are used by ecologists to do what?

Answer 5

to determine the distribution and abundance of species in an ecosystem (by sampling)

Question 6

Describe the levels of the food chain starting from a producer?

Answer 6

Producers are eaten by primary consumers, which in turn may be eaten by secondary consumers and then tertiary consumers

Question 7

What are predators?

Answer 7

Consumers that kill and eat other animals

Question 8

What are prey?

Answer 8

consumers that are eaten

Question 9

In a stable community, what is the relation between the numbers of predators and prey?

Answer 9

the numbers of predators and prey rise and fall in cycles

Question 10

Why is sampling carried out?

Answer 10

counting all of the individuals of a species can be difficult and time consuming

Question 11

What is most important when using sampling?

Answer 11

sampling should be representative of the whole area

Question 12

3 needed

What are the biotic factors that could affect distribution?

Answer 12

• trampling by humans
• grazing by sheep
• competition

Question 13

4 needed

What are the abiotic factors that could affect distribution?

Answer 13

• pH
• light intensity
• distance to stream
• application of fertiliser/weedkiller

Question 14

What do many different materials cycle through in an ecosystem?

Answer 14

many different materials cycle through the abiotic and biotic components of an ecosystem

Question 15

Why are all materials in the living world recycled?

Answer 15

to provide the building blocks for future organisms

Question 16

What does the carbon cycle do?

Answer 16

returns carbon from organisms to the atmosphere as carbon dioxide to be used by plants in photosynthesis

Question 17

How do microorganisms contribute to the carbon cycle?

Answer 17

Respiration by microorganisms decays dead plants and animals. releasing carbon dioxide.

This carbon dioxide can be used by plants in photosynthesis to make new biological molecules (carbohydrates, proteins and fats)

Question 18

When is carbon returned to the atmosphere?

Answer 18

when living organisms respire giving off carbon dioxide

Question 19

Water is continuously..

Answer 19

evaporated and precipitated

Question 20

What does the water cycle do?

Answer 20

provides fresh water for plants and animals on land before draining into the seas as water is continuously evaporated and precipitated

Question 21

How are mineral ions returned to the soil from animals and plants?

Answer 21

mineral ions are returned to the soil from dead animals and plant material when microorganisms break the dead material down

Question 22

What is decomposition?

Answer 22

The process of breaking down material

Question 23

3 needed

Which factors affect the rate of decay of biological material?

Answer 23

• temperature
• availability of oxygen
• water level

Question 24

How does temperature affect the rate of decay of biological material? (and how/why?)

Answer 24

Increases it

An increased temperature causes faster reactions (e.g. respiration)

or increased rate of enzyme action

Question 25

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

Answer 25

Increases it

Oxygen needed for aerobic respiration (and used to release energy)

Question 26

Gardeners and farmers try to provide what for decomposition?

Answer 26

optimum conditions for rapid decay of waste biological material

Question 27

What is the compost produced from decomposition used as?

Answer 27

a natural fertiliser for growing garden plants or crops

Question 28

What does anaerobic decay produce?

Answer 28

methane gas

Question 29

What are biogas generators used to do?

Answer 29

to produce methane gas as a fuel

Question 30

What would the fastest rate of decay indicate for that temperature?

Answer 30

It is at or near the optimum temperature

Question 31

Why might a farmer spread dead plant material onto his field?

Answer 31

Dead plant material contains nitrate ions

which leads to faster growth

Question 32

2 needed

Which microorganisms decay dead plant/animal material?

Answer 32

bacteria

fungi

Question 33

4 points

What role do producers play in the ecosystem?

Answer 33

Synthesise molecules/produce glucose by photosynthesis

Using light energy from the sun

and make carbon dioxide and water

and produce biomass for primary consumers

Question 34

6 marks

Describe the carbon cycle

Answer 34

• Photosynthesis by green plants / algae
• Removes CO₂ from atmosphere
• To make glucose
• Animals eat plants
• which transfers carbon compounds to them
• Both plants and animals respire, releasing CO₂ back into the atmosphere
• When plants and animals die
• The carbon compounds in their bodies are released as CO₂
• When microorganisms break down their bodies
• and respire

Question 35

What is a consequence to the living world of substances such as carbon not being recycled?

Answer 35

There would eventually be no building blocks for future organisms to build their bodies with

as there is a finite amount of molecules on Earth

Question 36

Why would a biogas generator produce more carbon dioxide over time when air is present?

Answer 36

Oxygen in air, which allows microorganism to respire aerobically, releasing carbon dioxide

Question 37

What role do microorganisms play in cycling nutrients through an ecosystem?

Answer 37

Return carbon to atmosphere as CO₂ when they respire

and release mineral ions into the soil

by process of decomposition

Question 38

How does water affect the rate of decay?

Answer 38

Many decomposers secrete enzymes onto decaying matter and then absorb any dissolved molecules. Without water these reactions cannot occur

likely removed content

Question 39

6 marks - VERY important to learn

Describe the carbon cycle

Answer 39

• (green) plants photosynthesise
• photosynthesis takes in carbon dioxide
• (green) plants use carbon to make carbohydrate / protein / fat / organic compounds / named (e.g. enzymes / cellulose)
• animals eat (green) plants (and other animals)
• (green) plants respire
• animals respire
• respiration releases carbon dioxide
• (green) plants and animals die
• microorganisms decay / decompose / rot / break down / feed on dead organisms
• microorganisms respire

Question 40

5 marks

A large amount of untreated sewage containing organic matter and bacteria entered the river. Many fish died, explain why.

Answer 40

bacteria decay organic matter

by digestion

bacteria respire aerobically

which lowers oxygen concentration (in water)

reduced energy supply causes death of fish

Question 41

A disease kills many of the (primary consumers). Why does the number of (producers) increase?

Answer 41

Fewer are eaten

Question 42

Why would a lower volume of biogas produced be lower at a lower temperature?

Answer 42

enzymes are denatured

so won’t work (as efficiently)

Question 43

How would limiting animals movement make food producing more efficient?

Answer 43

reduces energy transfer

Question 43

How would limiting animals movement make food producing more efficient?

Answer 43

reduces energy transfer

Question 44

Why might decomposition stop?

Answer 44

all dead plant/animal material decayed/decomposed