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EDEXCEL BIOLOGY > TOPIC 5: Ecosystems & Photosynthesis > Flashcards

TOPIC 5: Ecosystems & Photosynthesis Flashcards

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1
Q

Define ecosystem

A

a self-sustaining life-supporting environment with biotic and abiotic factors

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2
Q

What is an anthropogenic factor?

A

factors arising from human activity that affect survival

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3
Q

What determines the distribution and abundance of organisms in a habitat?

A
  • biotic and abiotic factors

- niche of an organism

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4
Q

What determines which niche an organism occupies?

A

adaptations to cope with biotic and abiotic factors

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5
Q

What is the biosphere?

A

global ecosystem, all organisms on earth

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6
Q

What is a biome?

A

major ecosystems on earth

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7
Q

How could you increase algal growth?

A
  • more light energy
  • more minerals for growth and to make chlorophyll
  • increase temperature to increase RoR
  • more CO2 or O2
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8
Q

What is the null hypothesis for the Student’s T-test?

A

There is no statistically significant difference between the means

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9
Q

When can the Student’s T-test be used?

A

when the data is normally distributed

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10
Q

When is the null hypothesis rejected?

A

when t exceeds the critical value at p=0.05

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11
Q

What does p=0.05 mean?

A

in 95% of cases where the study is repeated, the same conclusion would be found

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12
Q

What does the Spearman’s rank test determine?

A

stenght of a relationship, lying between +1 and -1

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13
Q

When is there a significant correlation in the Spearman’s rank test?

A

when rs is greater than the critical value

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14
Q

Define succession

A

a series of changes of organisms over a period of time

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15
Q

Define niche

A

role of an organism in the ecosystem

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16
Q

What is primary succession?

A

succession on inorganic surface devoid of any vegetation (bare rock, sand, etc.)

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17
Q

Describe the stages of primary succession

A
  1. Pioneer species (lichens & mosses) help break down the rock surface into rock grains, which form soil with dead inorganic matter
  2. Intermediate species (grasses, fern) can establish root systems in soil, which means more water and minerals are retained
  3. Climax community (forest) remains unchanged unless conditions change; biodiversity increases as trees influence rest of community
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18
Q

How does primary succession happen on sand dunes?

A

sand is unstable, lacks organic matter, is salty and dries out quickly so pioneer plants are xerophytes

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19
Q

What happens to humus % as the years go by?

A

increases & gets darker because organic matter increases

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20
Q

Why are there some tree-less climax communities?

A
  • the drainage is so good that the land is in drought so trees can’t grow, only mosses and lichens
  • bogs won’t progress to forest because it’s too cold and windy
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21
Q

What is secondary succession?

A

development of an ecosystem from existing soil that has been cleared of vegetation

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22
Q

How is secondary succession different to primary succession?

A

faster appearance of species because soil is already present, with minerals and microorganisms & there are already dormant seeds in the soil

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23
Q

What are the pioneer species in secondary successions likely to be?

A

Wind pollinated plants

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24
Q

What is deflected succession?

A

A community that is kept stable by human activity, which prevents succession from running its course

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25
Q

How is succession deflected?

A

Harvesting and deforestation prevent next species from living there because the land is bare again

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26
Q

Define climax community and explain why it’s stable

A
  • final stage of succession, where there is one dominant species
  • stable because there’s a balanced EQM of species
27
Q

Describe how to carry a study to compare distribution of (organism) on two different areas

A
  • measure off two areas of the same size
  • quadrat
  • random coordinates
  • random number generator
  • number of organisms / percentage cover
  • several sample sites used
  • collect data in table
28
Q

How can water availability be measured?

A

Moisture probe used to test soil around plants

29
Q

How might an increase in birds on an island increase plant biodiversity?

A
  • birds brought seeds with them
  • bird droppings add minerals to soil, supporting growth of more plants
  • faeces help maintain soil structure
30
Q

Explain the niche of plants

A
  • producer, so it produces food for other organisms
  • improves soil structure
  • provides shelter for organisms
31
Q

Describe the structure of chlorophyll a and b

A
  • hydrophilic head due to Mg2+ at centre of porphyrin ring

- hydrophobic tail due to hydrocarbon chain which anchors molecule into chloroplast membrane

32
Q

Describe the structure and function of carotenoids

A
  • hydrophobic

- assist chlorophyll a+b by passing light to them (accessory pigments)

33
Q

What light wavelengths do PS pigments absorb?

A
  • all absorb blue light

- carotenoids don’t absorb yellow to red

34
Q

What is the role of the outer membrane of a chloroplast?

A

allows passage of CO2, O2 and H2O

35
Q

What is the function of the inner membrane of a chloroplast?

A

contains transporter proteins

36
Q

Describe the structure and function of thylakoid membranes

A
  • interconnected, flat, fluid-filled sacs of membrane
  • contains photosynthetic pigments
  • LDRs happen here
37
Q

What is a granum?

A

stacks of thylakoids

38
Q

What is the stroma?

A
  • fluid surrounding thylakoids

- LIRs happen here

39
Q

What is the role of the DNA loop?

A

chloroplast DNA coding for some proteins

40
Q

What is the function of light dependent reactions?

A
  • production of ATP to supply energy for synthesis of carbohydrates
  • production of NADPH to supply H+ ions for synthesis of carbohydrates
41
Q

Equation for light dependent reactions

A

H2O + ADP + Pi + NADP+ —> 1/2 O2 + ATP + NADPH + H+

42
Q

How is ATP made from ADP?

A

ADP + Pi + energy —> ATP

phosphorylation

43
Q

What happens in the light dependent reaction?

A
  1. PS II P680 emits 2 excited e’s, which pass to acceptor which is reduced
  2. E’s lost replaced by photolysis of H2O
  3. E’s pass to a series of carriers along electron transport chain and each is reduced and oxidised
  4. Energy released as each carrier has a lower E level than the one before (synthesises ATP by photophosphorylation)
  5. PSI P700 emits 2 e’s and replaced by e’s from transport chain
  6. E’s captured by an e acceptor and passed down chain
  7. 2e’s combine with H+ to reduce NADP+ to NADPH and H+
44
Q

What does the photolysis of water produce?

A

2 H+, 2 e’s, and half O2

45
Q

What is the function of light independent reactions?

A

use NADPH and ATP to reduce CO2 to glucose

46
Q

Equation for light-independent reactions

A

CO2 + ATP + NADPH + H+ –> C6H12O6 + ADP + Pi + NADP+

47
Q

What happens in the Calvin cycle?

A
  • CO2 fixation: CO2 combines with RuBP to form 2 GP
  • Reduction: GP reduced to form GALP
  • Regeneration of RuBP: GALP resynthesises 6 RuBP and produces 1 glucose
48
Q

What turns CO2 and RuBP into 2GP?

A

RuBisCO

49
Q

How is GP reduced to GALP?

A

hydrogen from NADPH and energy from ATP

50
Q

What is an autotroph?

A

photosynthetic or chemosynthetic organisms

51
Q

What is a heterotroph?

A

consumer of other organisms

52
Q

What is a decomposer?

A

bacteria or fungi that feed on dead organic matter

recycler of nutrients

53
Q

What do food chains show?

A

flow of energy from one organism to another

54
Q

Define primary productivity

A

rate at which energy is incorporated into organic molecules (rate of PS)

55
Q

What is light energy lost to in photosynthesis?

A
  • transpiration
  • reflection
  • transmission
  • respiration
  • not useful wavelength
56
Q

What are the limiting factors for PS?

A
  • light
  • water from soil
  • temperature
  • C02 concentration
57
Q

Define gross primary productivity (GPP)

A

rate at which energy is incorporated into organic molecules

58
Q

What are the units for GPP?

A

kJm⁻²year ⁻¹

59
Q

Define NPP

A

rate at which energy is incorporated into organic molecules that make up new biomass

60
Q

How can you calculate NPP using GPP?

A

GPP - R

61
Q

Why might mammal respiration rate be higher than reptile respiration rate?

A

mammals are warm blooded so they use up more energy because it’s needed to keep their body temp constant

62
Q

Define secondary productivity

A

rate at which energy is used to make new consumer biomass

63
Q

Where does energy consumed go?

A
  • lost in respiration
  • lost in waste
  • make up biomass
64
Q

What factors affect respiration rate?

A
  • SA/V
  • time spent looking for food
  • temperature
  • digestibility of food

EDEXCEL BIOLOGY (14 decks)

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