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Biology > 13. ENERGY & ECOSYSTEMS > Flashcards

13. ENERGY & ECOSYSTEMS Flashcards

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1
Q

Where does the energy in ecosystems originally come from?

A

The sun

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2
Q

In which direction does the arrow go in a food chain?

A

In the direction of energy flow

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3
Q

What is each level in a food chain called?

A

A tropic level

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4
Q

List the trophic levels in a food chain

A

Producer, primary consumer, secondary consumer, tertiary consumer and quaternary consumer.

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5
Q

Why are plants producers?

A

Because they produce their own food in photosynthesis.

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6
Q

What percentage of the sun’s rays will be absorbed by a plant?

A

1-3%

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7
Q

Why will only 1-3% of the sun’s rays be absorbed by a plant?

A

Some will be reflected / absorbed by the atmosphere, some is the wrong wavelength to be absorbed by chlorophyll

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8
Q

How much energy is converted to new biomass in each trophic level?

A

5-20%

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9
Q

Why does the amount of biomass decrease at each trophic level?

A

Not all of the organism will be consumed, some parts of the organism are undigestable, some energy is lost as heat, and some energy is lost in respiration

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10
Q

Describe how to measure the biomass at a trophic level

A

Put organisms into an oven at a high temperature (100-150 degrees Celsius) until the water has evaporated. Then weigh the dry biomass.

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11
Q

How can you ensure all the water is evaporated when drying organisms?

A

Record the mass at intervals until it is constant

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12
Q

Describe how you can measure the energy within biomass

A

Use bomb calorimetry to burn the sample and record the temperature change of a known mass of water. Then use E = m x c x ∆T

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13
Q

What does the productivity of an ecosystem depend on?

A

Biotic factors such as plants, animals, fungi, and bacteria
Biotic factors are living things that have an impact on another population of living things/environment
Abiotic factors such as light intensity, temperature, availability of nutrients, soil pH, water
Abiotic factors are non living variables that affect the distribution of organisms in an ecosystem
Abiotic and biotic factors together make up an ecosystem

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14
Q

Define GPP

A

The total chemical energy store in a plant, in a given area or volume

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15
Q

What three other ways can you describe GPP?

A

The total biological molecules produced from photosynthesis, the total light energy absorbed by chlorophyll, and the total energy produced from photosynthesis

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16
Q

Name three factors that might affect the GPP of a plant at a given time

A

Light intensity, temperature and carbon dioxide concentration

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17
Q

Recall the equation to calculate NPP

A

NPP = GPP - R

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18
Q

Define NPP

A

The chemical energy store in a plant after respiratory losses

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19
Q

Recall the equation for N

A

N = I - (F + R)

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20
Q

Define N

A

It is the net production of consumers

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21
Q

Recall the units for productivity

A

kJ ha-1 year-1

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22
Q

Recall the equation for ecological efficiency

A

% efficiency = energy or biomass available after transfer / energy or biomass available after transfer x 100

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23
Q

Define ecological efficiency

A

The efficiency of energy transfer between trophic levels

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24
Q

Recall the factors that farmers may control to increase ecological efficiency

A

Light intensity, water availability, temperature, nutrient availability, pests, disease, energy lost as heat or in movement

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25
Q

Describe how farmers would increase light intensity

A

Use artificial lamps

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26
Q

Describe how farmers would increase water availability

A

Irrigating crops

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27
Q

Describe how farmers would control temperature of indoor crops

A

Use heaters to heat greenhouses to the optimum temperature

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28
Q

Describe how farmers would control temperature of animal pens

A

Use heaters to heat pens to the optimum temperature

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29
Q

Describe how farmers would increase available nutrients to crops

A

Fertilisers

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30
Q

Describe how farmers would increase available nutrients to animals

A

Provide nutrient rich food

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31
Q

Describe how farmers would reduce pests on crops

A

Spraying pesticides

32
Q

Describe how farmers would reduce disease on crops

A

Spraying fungicides

33
Q

Describe how farmers would reduce disease in animals

A

Antibiotics

34
Q

Describe how farmers would reduce energy lost in animal movement

A

Keeping them in pens

35
Q

Name one thing farmers might want to know about a new practice before they adopt it

A

Cost, side effects, whether the substances will affect other organisms, method of application (labour)

36
Q

Name phosphate-containing organic compounds

A

ATP/ADP, DNA/RNA, phospholipids, GP & TP

37
Q

What are saprobiotic bacteria?

A

Aerobic bacteria that decompose dead organic matter

38
Q

Why do plants grow more when more phosphates are available in the soil?

A

Because they can absorb more phosphates and use them to produce more phosphate-containing molecules for growth

39
Q

Describe the effect on the soil of removing harvested crops

A

Harvesting crops removes the minerals contained in the plant biomass from the ecosystem, depleting the soil

40
Q

How do farmers replenish mineral depleted soil?

A

Artificial fertilisers and / or natural fertilisers (manure)

41
Q

Why are artificial and natural fertilisers absorbed differently by plants?

A

Artificial fertilisers contain minerals in a form that is readily absorbed, whereas manure must be decompsed by saprobiotic bacteria first as the minerals are contained in organic matter

42
Q

Why might farmers choose to alternate the use of fields between grazing animals and growing crops?

A

Because the urine and manure from the grazing animals would re-enrich the soil

43
Q

Name nitrogen-containing organic compounds

A

Amino acids, ATP/ADP, DNA/RNA, NADP+

44
Q

Why do plants grow more when more phosphates are available in the soil?

A

Because they can absorb more nitrogen and use them to produce more nitrogen-containing molecules for growth

45
Q

Name the molecules involved in the nitrogen cycle

A

N2 (atmospheric nitrogen)

46
Q

Name the ions involved in the nitrogen cycle

A

NH4+ (ammonium), NO2- (nitrite), NO3- (nitrate)

47
Q

Which is the only form plants can absorb nitrogen in?

A

NO3- (nitrate)

48
Q

Name the four processes involved in the nitrogen cycle

A

Nitrogen fixation, nitrification, decomposition and denitrification

49
Q

Write an equation to show what happens in nitrogen fixation

A

N2→NH4+

50
Q

Which bacteria carry out nitrogen fixation?

A

Nitrogen fixing bacteria

51
Q

Name the two places nitrogen fixing bacteria live

A

Free living in the soil, and in root nodules of leguminous plants

52
Q

Nitrogen fixing bacteria have a mutualistic relationship with leguminous plants. What does this mean?

A

Both the bacteria and the plant benefit from the relationship. The bacteria gain sugars from the plant for respiration, and the plant gains nitrogen fixed by the bacteria

53
Q

What type of reaction is nitrogen fixation?

A

Reduction

54
Q

Write an equation to show what happens in nitrification

A

NH4+→NO2-→NO3-

55
Q

Which type of bacteria carry out nitrification?

A

Nitrifying bacteria

56
Q

What type of reaction is nitrification?

A

Oxidation

57
Q

Write an equation to show what happens in decomposition

A

Organic compounds→NH4+

58
Q

What type of bacteria carry out decomposition?

A

Saprobiotic bacteria

59
Q

Name the conditions necessary for saprobiotic bacteria to carry out decomposition

A

Aerobic

60
Q

Write an equation to show what happens in denitrification

A

NO3-→N2

61
Q

Which type of bacteria carry out denitrification?

A

Denitrifying bacteria

62
Q

What type of reaction is denitrification?

A

Reduction

63
Q

How would farmers use leguminous plants to re-enrich depleted soil?

A

They would grow them as a crop, then plough them into the soil

64
Q

Why would farmers grow leguminous crops on depleted soil, then plough them in?

A

To increase nitrogen fixation (because of the nitrogen-fixing bacteria on the root nodules). The plant would also be decomposed when ploughed in, increasing available minerals in the soil

65
Q

How could selective breeding produce a more efficient crop plant?

A

You could breed plants for increased nutrient uptake

66
Q

Why would ploughing the soil increase available nutrients?

A

It would aerate the soil, increasing decomposition

67
Q

Why would growing the same crops on a field eventually deplete it?

A

Crops absorb one particular nutrient more than most, therefore the soil would become deficient in this nutrient as the crops were harvested

68
Q

Why does rotating crops reduce soil nutrient depletion?

A

Because different crops absorb different nutrients, preventing the soil becoming depleted in one particular mineral

69
Q

What is leaching?

A

When rain washes fertiliser into rivers and lakes

70
Q

Why does leaching happen more from a fallow field?

A

Crops absorb some of the fertiliser, and the soil becomes more compact when crops are grown in it

71
Q

Name the process that causes organisms in a lake to die because of leaching

A

Eutrophication

72
Q

What is the first thing that leaching produces in rivers and lakes?

A

An algae bloom

73
Q

What does an algae bloom cause?

A

Aquatic producers die because light cannot penetrate into the lake, so they can’t photosynthesise

74
Q

What happens when the aquatic producers in rivers and lakes die?

A

Saprobiotic bacteria decompose them, using up oxygen in the lake

75
Q

What does the oxygen depletion in the lake cause?

A

It causes aerobic organisms e.g. fish to die

76
Q

How does the death of aerobic organisms in rivers and lakes perpetuate eutrophication?

A

Because more decompsition occurs, which means the saprobiotic bacteria use up even more of the oxygen

Biology (26 decks)

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