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Biology A level (Edexcel SNAB) > UNIT 5 - 'On the wild side' (ecosystems, photosynthesis and climate change) > Flashcards

UNIT 5 - 'On the wild side' (ecosystems, photosynthesis and climate change) Flashcards

excepto p102-105 y 113

1
Q

What is meant by ecosystem?

A

The biotic factors, like living organisms, and abiotic factors, such as climate, in an area.

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2
Q

What is meant by habitat?

A

The place where an organism lives.

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3
Q

What is meant by population?

A

All the organisms of one species in one area.

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4
Q

What is meant by community?

A

All the organisms of different species that live and interact in the same habitat.

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5
Q

What is meant by biotic factors?

A

The living features of an ecosystem (i.e. predators or food)

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6
Q

What is meant by abiotic factors?

A

The non-living features of an ecosystem (i.e. temperature or availability of water).

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7
Q

What is interspecific competition and how does it arise?

A

The competition between different species. i.e. two species share the same source of food and so when there’s a shortage, both species compete for the food and the populations can’t grow much.

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8
Q

How does this graph sow intraspecific population?

A
  1. When there’s plenty of resources, the population increases, and so does competition.
  2. Eventually resources become limiting because of the increasing competition and so the population begins to decline.
  3. In the smaller population, there’s less competition for resources and so the population starts to grow again.
  4. The maximum stable population size of a species that an ecosystem can support is the carrying capacity.
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9
Q

What is the carrying capacity?

A

The maximum stable size of a species that an ecosystem can support.

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10
Q

The lynx is the predator and the snowshoe hare is the prey.

What happens at each of the stages in the graph?

A
  1. As the prey population increases, there’s more food available and so the predator population grows.
  2. As the predator population increases, more prey is eaten and so the prey population starts to fall.
  3. As prey population falls, there’s less food for the predators and so the predator population also falls.
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11
Q

How does distribution of a species vary due to abiotic and biotic factors?

A

Abiotic: Orientation (for higher solar input), minerals in soil, temperature in some regions is too low/high.

Biotic: Species may be out-competed in some areas where other species are dominant so they will grow in other areas.

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12
Q

What is a niche?

A

Role of a species within its habitat, including biotic interactions (such as the organism it eats) and abiotic interactions (such as the oxygen consumed and carbon dioxide excreted). Every species has its own niche.

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13
Q

Can two species occupy the same niche? Why?

A

No. every species has its own niche.

Otherwise, the species would compete (i.e. for the same food source) and therefore the populations would decrease.

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14
Q

What is succession?

A

The process by which an ecosystem changes.

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15
Q

When does primary succesion happen?

A

When land has been newly exposed or fromed, so there’s no soil to start with.

(i.e. Volcano has erupted exposing new land, sea level has dropped, exposing new land)

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16
Q

When does secondary succession happen?

A

When a land has been cleared of all plants but the soil remains.

(i.e. after a forest fire)

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17
Q

How does primary succession come about?

A
  1. Seeds and spores are blown by the wind and they begin to grow in harsh abiotic conditions. These pioneer species are the first to colonise the area.
  2. Pioneer species start to change the abiotic conditions - they die and microorganisms decompose the organic material (humus) into soil, or decompose rocks.
  3. The abiotic conditions are less harsh (i.e. more soil to retain water) and bigger, better adapted to the new conditions species grow there, adding to the richness of soil and minerals when they die. They also outcompete some of the first species that aren’t adapted to the new conditions.
  4. Biodiversity keeps increasing until the climax community is reached - the largest, most complex community of plants and animals the ecosystem can support.
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18
Q

What is the climatic climax?

A

The climax ccommunity for a specific climate.

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19
Q

What is the climax community called when succession is stopped artificially?

A

Plagioclimax

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20
Q

What is phosphorylation?

A

Adding phosphate to a molecule.

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21
Q

What is photophosphorylation?

A

Adding phosphate to a molecule using light.

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22
Q

What is photolysis?

A

The splitting of a molecule using light.

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23
Q

What is hydrolysis?

A

The splitting of a molecule using water.

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24
Q

What is the chemical equation for photosynthesis?

A

6CO2 + 6H2O > C6H12O6 + 6O2

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25
Q

What is a coenzyme?

A

A molecule that aids the function of an enzyme by transferring a chemical group from one molecule to another.

26
Q

How does NADP work as a coenzyme?

A

Transfers hydrogen from one molecule to another.

NADP + e- + H+ > NADPH

NADPH > NADP + e- + H+

27
Q

Why do thylakoids need to have a high surface area?

A

To absorb as much light as possible, since the photosystems, and therefore the pigments, are located in its membrane.

28
Q

Why do thylakoids membranes contain lots of ATP synthase?

A

To produce ATP in the light-dependent stage of photosynthesis.

29
Q

What photosynthetic pigments do chlorplasts contain?

A

Chlorophyll a, chlorophyll b and carotene.

30
Q

What is a photosystem?

A

Pigments attached to a protein.

31
Q

What wavelength of light does photosystem I (PSI) absorb best?

A

700nm

32
Q

What wavelength of light does photosystem II (PSII) absorb best?

A

680nm

33
Q

What does the stroma contain to aid photosynthesis?

A

Enzymes, sugars and organic acids required for the light-independent reaction to take place.

34
Q

What is A?

A

PSII (Photosystem II)

35
Q

What is B?

A

PSI (photosystem I)

36
Q

Give the equation C

A

2H2O > 4H+ + 4e- + O2

37
Q

What do the electrons released by photolysis do?

A

They replace the excited electrons that have left the photosystem.

38
Q

Does cyclic phosphorylation synthesise NAPDH?

A

No. Only produces ATP.

39
Q

Explain the light dependent stage.

A
  1. Electrons are excited in PSII and leave the photosystem with high energy and enter the ETC (electron transport chain).
  2. The electrons in the photosystem are replaced by the electrons produced during the photolysis of water.
  3. The moving electrons through the ETC release energy which is used by the proton pump to create a proton gradient across the thylakoid membrane. (Thylakoid has higher conc. of protons that the stroma)
  4. The protons then flow down a concentration gradient through the ATP synthase, which uses that energy to phosphorylate ADP into ATP.
  5. Electrons are further excited in PSI. They are used for the reduction of NADP or are recycled and are used for cyclic phosphorylation.
40
Q

What happens at D?

A

Reduction of NADP.

NADP + e- + H+ > NADPH

41
Q

Compared to non-cyclic phosphorylation, does cyclic phosphorylation produce high amounts of ATP?

A

No. Only small amounts.

42
Q

Where does the light depednet stage occur?

A

In the thylakoid membrane.

43
Q

When a proton gradient is created across the thylakoid membrane, which side has the highest/lowest conc of H+ ions?

A

Thylakoid has higher concentration of protons than the stroma.

44
Q

What is A?

A

The enzyme RUBISCO.

45
Q

What is B?

A

2 molecules of glycerate-3-phosphate

46
Q

What is C?

A

2 molecules of Glyceraldehyde 3-phosphate (GALP)

47
Q

What is D?

A

Ribulose biphosphate (RuBP)

48
Q

Describe the Calvin cycle

A
  1. 1 molecule of CO2 is fixated into RuBP using the enzyme RUBISCO to give an unstable 6-carbon compound that breaks to give 2 molecules of GP.
  2. 2 molecules of ATP and 2 molecules of NADPH are used to give 2 molecules of GALP. (1 of every 6 produced are used to produce a hexose sugar).
  3. The remaining GALP then react, using ATP to form RuBP (5 carbons)
49
Q

What are the actual ratios for 1 molecule of glucose?

A
50
Q

How are carbohydrates made from the products of the Calvin cycle?

A

2 GALP molecules are used to make a hexose sugars (i.e. glucose) that can then join in different ways to form complex carbohydrates.

51
Q

How are lipids made from the products of the Calvin cycle?

A

Glycerol is synthesised from GALP and fatty acids are synthesised from GP.

52
Q

How are amino acids made from the products of the Calvin cycle?

A

Some amino acids are made from GP.

53
Q

How are nucleic acids made from the products of the Calvin cycle?

A

The sugar in RNA (ribose) is made from GALP.

54
Q

About what percentage of the energy available to one trophic level is passed on to the next trophic level?

A

10%

55
Q

Draw a diagram to show how the energy available to one trophic level is passed on to the next trophic level.

A
56
Q

Why is not all of the energy available for a trophic level not taken in by the organisms in the first place?

A

Plants can’t absorb all the light for photsynthesis (some is reflected) and there are parts of the plants that can’t photosynthesise (i.e. the bark of a tree).

Some parts of food can’t be eaten by organisms (i.e. bones) and some are indigestible, so are excreted as faeces.

57
Q

Why is not the energy absorb used as biomass?

A

The majority is lost as heat or movement (respiratory loss).

58
Q

What is the gross productivity?

A

The energy taken in (absorbed) by a trophic level.

59
Q

What is net productivity?

A

The energy that becomes biomass. (energy available to next trophic level).

60
Q

What is the equation relationg net productivity, gross productivity and respiratory loss?

A

Gross productivity - respiratory loss = net productivity

61
Q

What does gross primary productivity (GPP) and net primary productivity (NPP) refer to?

A

The gross productivity and net productivity of the first trophic level (the producers).

62
Q
A

Biology A level (Edexcel SNAB) (5 decks)

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