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A-level Biology > 5B - Energy transfer in ecosystems > Flashcards

5B - Energy transfer in ecosystems Flashcards

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1
Q

What do plants photosynthesise and produce?

A

biomass

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2
Q

What does an ecosystem include?

A

All the organisms living in a particular area and all the non-living (abiotic) conditions.

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3
Q

What are producers?

A

Organisms that make their own food.

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4
Q

What are organisms that make their own food called?

A

Producers.

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5
Q

Give an example of a producer

A

Plants and algae

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6
Q

Why are plants and algae producers?

A

Because they produce their own food through photosynthesis.

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7
Q

How do producers like plants and algae produce their own food?

A

Through photosynthesis.

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8
Q

How do producers photosynthesise to produce their own food?

A

During photosynthesis plants use energy (from sunlight) and carbon dioxide (from the atmosphere in land-based ecosystems, or dissolved in water in aquatic ecosystems) to make glucose and other sugars.

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9
Q

What happens to the sugars (glucose) produced during photosynthesis?

A

Some are used in respiration, to release energy for growth.

The rest is used to make other biological molecule, such as cellulose.

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10
Q

What do the biological molecules make up?

A

Biomass.

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11
Q

What is biomass?

A

The total mass of living material in a specific area at a given time.

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12
Q

What can biomass also be thought of as?

A

The chemical energy stored in a plant.

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13
Q

How is energy transferred through the living organisms of an ecosystem?

A

When organisms eat other organisms.

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14
Q

What are producers eaten by?

A

Primary consumers.

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15
Q

What are primary consumers eaten by?

A

Secondary consumers.

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16
Q

What are secondary consumers eaten by?

A

Tertiary consumers.

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17
Q

What is a saprobiont?

A

A decomposer.

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18
Q

How can biomass be measured?

A

As dry mass or by using a calorimeter.

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19
Q

What can biomass be measured in terms of?

A

The mass of carbon that an organism contains or the dry mass of its tissue per unit area.

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20
Q

What is dry mass?

A

The mass of the organism with the water removed.

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21
Q

How do you measure dry mass?

A

A sample of the organism is dried, often in an oven set to a low temperature. The sample is then weighed at regular intervals (e.g. every day). Once the mass becomes constant you know that all the water has been removed.

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22
Q

How do you know that you have removed all the water from an organism to get the dry mass?

A

Once the mass becomes constant you know that all the water has been removed.

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23
Q

Why is dry mass used as a measure of biomass rather than wet mass?

A

Because the water content of living tissues varies.

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24
Q

What is a typical unit for dry mass?

A

kg m^-2 (dry mass per given area).

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25
Q

What is the mass of carbon present generally taken to be?

A

50% of the dry mass.

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26
Q

How can you estimate the amount of chemical energy stored in biomass?

A

By burning the biomass in a calorimeter.

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27
Q

How can calorimetry be used to measure biomass?

A

A sample of dry biomass is weighed then burnt in pure oxygen (in a sealed chamber called a bomb) and the energy released is used to heat a known volume of water. The change in temperature of the water is used to calculate the chemical energy of the dry biomass.

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28
Q

What is energy measured in?

A

Joules (J) or kilojoules (kJ).

29
Q

What is fresh mass?

A

Biomass + water.

30
Q

Why is using fresh mass good?

A

Easy to access.

31
Q

Why is using fresh mass bad?

A

Different plants/animals have varying amounts of water.

32
Q

Why is using dry mass good?

A

More reliable.

33
Q

What is using dry mass bad?

A

Organisms have to be killed. Time consuming and sometimes is not representative.

34
Q

What is the main issue with using biomass as a way of investigating populations?

A

Samples may not be representative.

35
Q

What is it better to use as opposed to biomass or numbers?

A

Energy.

36
Q

How can you determine the dry mass (biomass) of the total population/the area being investigated?

A

Scale up the result from the sample if needed.

37
Q

How is energy lost from the sun to the producer?

A
  • Over 90% of the sun’s energy is reflected back to space.
  • Not all wavelengths of light can be absorbed (e.g. green light).
  • Light may not fall on a chlorophyll molecule.
38
Q

How is energy lost from the producer to the primary consumer?

A
  • Much of the plant material can’t be accessed.
  • Some material can’t be digested.
  • Excretory losses.
  • Respiratory losses (in endotherms only).
  • Death and decay.
39
Q

How is energy lost between consumers?

A
  • Excretory losses.
  • Respiration.
  • Indigestible material (e.g. bones).
  • Death and decay.
40
Q

What are GPP and NPP types of?

A

Chemical energy stores.

41
Q

What does GPP stand for?

A

Gross primary production.

42
Q

What is GPP?

A

The total amount of chemical energy converted from light energy by plants, in a given area.

43
Q

What is the equation linking GPP and NPP?

A

NPP = GPP - R

44
Q

What does the R mean in the equation that links NPP and GPP?

A

Respiratory losses.

45
Q

How is approximately 50% of the GPP lost?

A

To the environment as heat when plants respire (respiratory losses - R).

46
Q

Approximately how much GGP is lost to the environment as heat when plants respire (respiratory losses - R)?

A

Approximately 50%.

47
Q

What does NPP stand for?

A

Net primary production.

48
Q

What is NPP?

A

The energy available to the plant for growth and reproduction - the energy stored in the plant’s biomass. It is also the energy available to organisms at the next stage in the food chain (the next trophic level). These include herbivores and decomposers.

49
Q

What are herbivores?

A

Animals that eat the plants.

50
Q

What is primary production often expressed as?

A

A rate - e.g. the total amount of chemical energy (or biomass) in a given area, in a given time.

51
Q

What are typical units of primary production?

A

kJ ha^-1 year^-1 (kilojoules per hectare per year) or kJ m^-2 yr^-1.

52
Q

What is is called when primary production is expressed as a rate?

A

Primary productivity.

53
Q

What is primary productivity.

A

When primary production is expressed as a rate.

54
Q

When do plants convert light energy to chemical energy?

A

During photosynthesis.

55
Q

How do you work out NPP in plants?

A

NPP = GPP - R

56
Q

How do you work out NPP in consumers?

A

NPP = I - (F + R)

57
Q

Where do consumers store chemical energy?

A

In their biomass.

58
Q

How do consumers get energy?

A

By ingesting plant material, or animals that have eaten plant material.

59
Q

Roughly how much of the total available energy is lost?

A

90%.

60
Q

What happens to the energy left after losses?

A

It is stored in the consumers’ biomass and is available to the next trophic level.

61
Q

What is the energy left after losses called?

A

The consumers’ net production.

62
Q

How can the net production of consumers be calculated?

A

N = I - (F + R)

63
Q

What does the N stand for in the equation to work out net production?

N = I - (F + R)

A

NPP - net primary production.

64
Q

What does the I stand for in the equation to work out net production?

N = I - (F + R)

A

Chemical energy in ingested food.

65
Q

What does the F stand for in the equation to work out net production?

N = I - (F + R)

A

Chemical energy lost in faeces and urine.

66
Q

What does the R stand for in the equation to work out net production?

N = I - (F + R)

A

Energy lost through respiration.

67
Q

What can the net production of consumers also be called?

A

Secondary production (or secondary productivity when it’s expressed as a rate).

68
Q

How do you calculate the efficiency of energy transfer (what is the equation)?

A

Efficiency = (Energy available after the transfer / Energy available before the transfer) x 100.

A-level Biology (42 decks)

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