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A Level Biology > Energy Transfer and Nutrient Cycles (Topic 5B) > Flashcards

Energy Transfer and Nutrient Cycles (Topic 5B) Flashcards

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1
Q

an ecosystem is…

A

all the organisms living in a particular area and all the abiotic conditions

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2
Q

producers are…

A

organisms that make their own food

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3
Q

biomass is the…

A

mass of living material in a plant

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4
Q

why is biomass of a plant used instead of wet mass?

A

water content varies

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5
Q

how do you know that all the water has been removed from a mass sample?

A

when mass becomes constant

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6
Q

gross primary production is…

A

the total amount of chemical energy converted from light energy by plants in a given area

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7
Q

respiratory losses is…

A

the chemical energy lost when plants respire

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8
Q

net primary production =

A

GPP - R

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9
Q

the net production of producers can be calculated by…

A

N = I - (F + R)
I = energy ingested by food
F = energy lost in faeces and urine
R = respiratory losses

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10
Q

% efficiency of energy transfer =

A

(net production of trophic level / net production of previous trophic level) x 100

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11
Q

as you move up the food chain energy transfers become…

A

more efficient

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12
Q

farmers increase efficiency in two ways:

A
  1. the energy lost to other organisms can be reduced through simplification of food webs
  2. the energy lost through the respiration of livestock
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13
Q

how and why are food webs simplified?

A

getting rid of side chains that don’t involve humans so energy losses are reduced. so pests are killed by pesticides

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14
Q

how are respiratory losses reduced?

A

controlling conditions animals live in so more of their energy is used for growth and less for respiration

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15
Q

a food chain shows….

A

simple lines of energy transfer in an ecosystem

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16
Q

a food web shows….

A

lots of food chains in an ecosystem and how they overlap

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17
Q

what do saprobionts do?

A

feed on remains of dead plants and animals, breaking them down

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18
Q

saprobionts ______ digest their food and secrete enzymes then….

A

externally
absorb the nutrients they need

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19
Q

saprobiotic nutrition is..

A

obtaining nutrients from dead organic matter and animal waste using extracellular digestion

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20
Q

some fungi form symbiotic relationships with the roots of plants. this is known as…

A

mycorrhizae

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21
Q

why are mycorrhizae relationships useful to plants?

A

increased SA of roots so greater water and nutrients will be absorbed

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22
Q

the 4 main processes of the nitrogen cycle are…

A
  1. nitrogen fixation
  2. ammonification
  3. nitrification
  4. denitrification
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23
Q

the first stage of the nitrogen cycle is…

A

nitrogen fixation

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24
Q

the second stage of the nitrogen cycle is….

A

ammonification

25
Q

the third stage of the nitrogen cycle is…

A

nitrification

26
Q

the fourth stage of the nitrogen cycle is…

A

denitrification

27
Q

what happens during nitrogen fixation?

A
  1. atmospheric nitrogen gas is converted into nitrogen-containing compounds
  2. producing ammonia, which forms ammonium ions that can then be used by plants
  3. they form a mutualistic relationship the plants provide them with carbohydrates and they provide the plant with nitrogen compounds
28
Q

what happens during ammonification?

A

nitrogen compounds from dead organisms are turned into ammonia by saprobionts which then form ammonium ions

29
Q

what happens during nitrification?

A

ammonium ions in the soil change into nitrites then to nitrates that can be used by plants

30
Q

what happens during denitrification?

A

nitrates in soil are converted into nitrogen gas by denitrifying bacteria

31
Q

what do plants use phosphorous for?

A

to make biological molecules like phospholipids, DNA and ATP

32
Q

describe the role of microorganisms after a field of crops is ploughed
(5 marks)

A
  1. microorganisms break proteins down
  2. ammonification
  3. conversion to nitrates
  4. by nitrifying bacteria
  5. nitrates absorbed into roots of new crops
33
Q

why are phosphates needed by a growing plant?
(3 marks)

A
  1. for production of phospholipids in cell membrane
  2. synthesis of ATP
  3. production of DNA
34
Q

why is it important for a farmer to reduce the leaching of nitrates?
(2 marks)

A

fewer nitrates in the soil for the next crop requiring more application of fertiliser needed

35
Q

the first step of the phosphorous cycle is…

A

phosphate ions are released into the rock by weathering

36
Q

the second step of the phosphorous cycle is…

A

phosphate ions are taken into the plants through the roots

37
Q

the third step of the phosphorous cycle is…

A

phosphate ions are transferred through the food chain as animals eat plants that are then eaten by animals

38
Q

the fourth step of the phosphorous cycle is…

A

phosphate ions are lost from the animals in waste products

39
Q

the fifth step of the phosphorous cycle is…

A

when plants and animals die saprobionts break down the organic compounds, releasing phosphate ions into the soil for assimilation by plants

40
Q

when rocks are weathered they release phosphate ions into the soil and…..

A

seas, lakes and rivers

41
Q

any phosphate ions released from rocks into water are taken up by…

A

algae

42
Q

explain how the use of inorganic fertilisers on fields leading to a lake no longer having any plants or fish anymore

6 marks

A

the run off of fertilisers
leads to increased algae growth
increases competition for light
causing death of plants
which increases food supply for microorganisms
respiration of microorganisms used up oxygen
fish die die to lack of oxygen

43
Q

explain how including leguminous plants in a crop rotation reduces the need to use artificial fertilisers

2 marks

A

they contain nitrogen fixing bacteria in foods so when the die they add nitrogen containing compounds to the soil

44
Q

application of very high concentrations of fertiliser to the soil causes plants to wilt. explain why

2 marks

A

lower water potential in soil than in the plant which prevents roots from taking up water

45
Q

nutrients are lost from the system when..

A

crops are harvested so aren’t left to decompose and when animals or animal products are removed from the area

46
Q

why are fertilisers used?

A

to replace lost minerals in soil

47
Q

why is it important to replace lost minerals in the soil?

A

so more energy can be used for growth, increasing the efficiency of energy transfer

48
Q

fertilisers can be ______ or ______

A

natural
artificial

49
Q

artificial fertilisers are….
which means…

A

inorganic
which means they contain pure chemicals as powders or pellets

50
Q

natural fertilisers are…
which include…

A

organic matter
manure, composted vegetables, crop residues and sewage sludge

51
Q

leaching is…

A

when water-soluble compounds in soil are washed away often into ponds or rivers nearby

52
Q

leaching can lead to…

A

eutrophication

53
Q

is leaching more likely with artificial or natural fertiliser?

A

artificial

54
Q

why is leaching less likely to occur with natural fertiliser?

A

they contain nitrogen and phosphorous which need to be decomposed by microorganisms before plants can absorb them. meaning their release is more controlled

55
Q

describe the process of eutrophication

A
  1. mineral ions leached from fertilised fields stimulate rapid growth of algae in ponds and rivers
  2. large amounts of algae block light from reaching plants below
  3. so plants die as they can’t photosynthesise
  4. bacteria feed on dead plants, meaning no. of bacteria increases
  5. the increased no. of bacteria reduces O2 conc in water by aerobically respiring
  6. fish die because there isn’t enough dissolved oxygen
56
Q

producers are also known as…

A

autotrophs

57
Q

use your knowledge of NPP to explain why freshwater marshes have a high carbon use efficiency and an advantage of this
2 marks

A

there is low respiration
so more growth occurs

58
Q

freshwater marsh soils are waterlogged creating anaerobic conditions.

use your knowledge of nitrogen cycle to suggest why these soils contain relatively high concentrations of ammonium compounds and low concentrations of nitrite and nitrate ions.

2 marks

A

nitrification occurs less

so less ammonium ions in soil aren’t changed into nitrogen compounds by bacteria changing them into nitrites and nitrates

A Level Biology (19 decks)

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