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A-Level OCR Biology > Unit 6 - Ecosystems > Flashcards

Unit 6 - Ecosystems Flashcards

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1
Q

Define Ecosystem

A

All the interactions between the living and non-living components in a defined area

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2
Q

Biome

A

Large ecosystem

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3
Q

Open ecosystem

A

When living things can move between ecosystems

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4
Q

Closed ecosystems

A

When living things cannot easily move between ecosystems e.g. islands

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5
Q

Niche

A

Role of a particular species

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6
Q

Biotic

A

Involves other living organisms

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7
Q

Biotic factors affecting ecosystems

A 
Predators
Food supply (prey)
Disease 
Cooperation between species 
Competition between species
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8
Q

Abiotic factors affecting ecosystems

A 
pH
Conc of pollutants 
Temp  (climatic)
Moisture/ rainfall/ relative humidity 
O2 level
Soil type (edaphic)
Light intensities
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9
Q

How does low light intensity affect the ecosystem

A

Plants develop photosynthetic pigments that require less light
Grow larger leaves
Reproductive systems that only work in optimum light intensities

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10
Q

How does temp affect the ecosystem

A

Temp has the biggest effect on enzymes in the organisms that live in the ecosystem
May trigger migration/ hibernation
Dormancy/ leaf fall/ flowering in plants

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11
Q

How are ecosystems organised

A

In trophic levels

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12
Q

Producers in an ecosystem

A

Lowest trophic level

Involves autotrophs, chemotrophs and photoautotrophs

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13
Q

Autotrophs

A

Convert energy from environment into complex organic matter, then are used as respiratory substrates or for growth

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14
Q

Chemo/photoautotrophs

A

Use light/ chemicals to convert small inorganic molecules into complex organic ones

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15
Q

Consumers

A

Higher/est trophic levels
Feed on complex organic matter made by autotrophs and other organisms and use the products of digestion as respiratory substrates or for growth
1’<2’<3’

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16
Q

Decomposers

A

Feed on waste or dead organsims to gain energy by digesting and respiring organic matter
Recycling - returns inorganic ions to the air/soil

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17
Q

Why are ecosystems dynamic

A

Always changing due to many interlaced intearctions that any small change causes several others–> alters flow of biomass

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18
Q

Types of changes in ecosystems

A

Cyclical - repeated change e.g. seasons, day/night
Directional - in one direction e.g.global warming, erosion
Unpredictable/ erratic - no rhythm or constant direction e.g. volcanic eruption

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19
Q

Trophic level

A

Level at which an organism feeds

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20
Q

Components of an ecosystem

A

Habitat
Population
Community

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21
Q

Habitat

A

Where an organism lives

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22
Q

Population

A

Where all the members of a species living in some place at a given time

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23
Q

Community

A

All the populations of diff species who live in some place at a given time, who can interact w/ each other

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24
Q

Why are there fewer consumers at higher levels

A

Energy (biomass) is lost at each trophic level so unavailable to organism at next trophic level, therefore there’s less energy available to sustain living tissue

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25
Q

How is biomass lost

A

Cellular respiration - conversion to inorganic molecules such as CO2 and H2O
Excretory materials
Indigestible matter
Not everything is fit for consumption e.g. bones
Transferred at metabolic heat (movement)

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26
Q

Loss of biomass in endotherms vs ectotherms

A

Ectotherms use less energy in maintaing body heat so there is more biomass availabe

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27
Q

Saprotrophs

A

Secrete extracellular enzymes onto dead/waste materials

Digest the materials into small molecules which are then absorbed and stored/respired

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28
Q

Why is the producer efficiency v. low

A

Approx 90% of light is reflected, unusable wavelength and transmitted through leaf
Limiting factors
Energy used for photosynthetic reactions

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29
Q

Succession

A

Progressive change in the structure and species composition in a community
Affects vegetation first but then brings about corresponding changes in bacteria, fungi, insects, birds and mammals

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30
Q

Climax community

A

Final, stable community that exists after the process of succession has occurred
Usually woodland communities

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31
Q

Deflected succession

A

Happens when succession is stopped/interfered w/ e.g. grazing so a plagioclimax develops as the species are stuck in that one stage of succession

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32
Q

Pioneer species

A

Species that begin the process of succession, often colonising an area as the first living thing there

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33
Q

Primary succession

A

If a community is developed from bare ground e.g. volcanic eruptions
Pioneer communities start succession —> conditions change (build up or organic material /nutrients) and other species succeed them
Larger plants continuously succeed small plants until a climax community is formed

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34
Q

Secondary succession

A

Does not start from bare ground

Takes place on a previously colonised but damaged/disturbed habitat

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35
Q

Why are sand dunes helpful in terms of succession

A

Shows us the stages of succession in order of occurrence whereas usually we only see the current stage

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36
Q

How does succession affect species diversity

A

Increases it however dominant species may outcompete the smaller species killing whole species off

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37
Q

Weathering

A

Breakdown or decomposition of rock in situ

38
Q

How does weathering contribute to succession

A

Decomposition of rock increases soil depth/ changes soil composition
Favouring new species

39
Q

Calculating net primary production

A

Gross primary production = npp - products of respiration

40
Q

Calculating efficiency of energy transfer

A

Net production/ food intake x 100

41
Q

Plagioclimax

A

Sub-climax community when succession has been deflected

42
Q

Ways to deflect succession

A 
Mainly agriculture and human activity e.g. Grazing 
Burning 
Application of fetilisers 
Application to herbicide 
Exposure to excessive amounts of wind
43
Q

How does succession affect biomass

A

Increases it due to more organisms in the ecosystem

44
Q

Why should sub-climax communities be conserved

A

Higher species diversity than climaxx communities - still contain some sub-climax species and climax species
Results in conserving a much wider range of plants and animals that dont live in the climax community

45
Q

Pioneer species on sand dunes

A

Species that can tolerate salty water, lack of fresh water and stable sand e.g. sea rcket

46
Q

Pioneer species on bare rock

A

Algae and lichens as they don’t need to be anchored into the soil

47
Q

Increasing primary productivity

A 
Some crops are planted early 
Irrigating crops 
Drought resistant crops 
Using greenhouses 
Crop rotation 
Fertilisers (provides inorganic ions)
Pesticides/ pest resistant crops
48
Q

How does planting some crops early increase primary productivity

A

Provides a longer growing season to harvest more light

49
Q

How does irrigating crops increase primary productiviy

A

Water is readily available for the light dependent stage of photosynthesis even when rainfall is below average

50
Q

How does growing crops in a greenhouse increases primary productivity

A

Provides a warmer temp —> increases the rate of photosynthesis

51
Q

How does crop rotation increase primary productivity

A

Stops reduction in soil levels of inorganic ions e.g. K^+ or NO3^-

52
Q

Crop rotation

A

Growing a diff. crop in each field on a rotational cycle

53
Q

How does use of pesticides increase primary productibity

A

Prevents loss of biomass and lowering yield of plant

54
Q

Why do plants need NH4+

A

Maintains pH

55
Q

Why do plants need NO3-

A

Part of the nitrogen cycle

56
Q

Function of K+ in plants

A

Improves growth of leaves

57
Q

Function of PO4 3- in pants

A

Improves growth of roots

58
Q

Increasing secondary productivity

A 
Harvesting animals before adulthood
Selctive breeding 
Animals treated w/ antibiotics 
Zero grazing 
Keeping environmental temp constant - prevents energy loss through homeostasis
59
Q

How does harvesting animals before adulthood increase secondary productivity

A

Minimises loss of energy as younger animals invest a larger proportion of energy into their growth

60
Q

How does selective breeding increase secondary productivity

A

Produces improved animal breeds w/ faster growth, increased egg production and increased milk production

61
Q

Zero grazing

A

Bringing food directly to animals

Maximises energy allocated to developing muscle by reducing need to move

62
Q

Processes in the carbon cycle

A 
Photosynthesis 
Respiration (animals and plants) 
Anaerobic respiration (dead organic matter and excreta)
Fossilisation
Combustion
Diffusion and carbonic acid formation  
Diffusion
Decomposition
Feeding
Sedimentation
63
Q

Processes adding to atmospheric CO2

A

Respiration
Combustion
Diffusion frm the sea to the air

64
Q

Processes removing atmospheric CO2

A

Photosynthesis

Diffusion and carbonic acid formation in the ocean

65
Q

Sedimentation

A

CO2 is used by plankton to produce calcium carbonate shells. When these die, their shells sink to the ocean floor and are buried by sediment

66
Q

Fossilisation

A

Organic matter is buried and copressed over millions of years forming gas, coal and oil

67
Q

Human interferences that affect the carbon cycle

A

Combustion
Population size (respiration and waste)
Deforestation
Farming

68
Q

Effects of human interences w/ the carbon cycle

A 
Global warming/enhanced greenhuse effect
Ocean acidification from carbonic acid 
Warmer sea - less CO2 absrbed 
Removing photosynthesisers 
Releasing more CO2 through combustion of trees
69
Q

Processes in the nitrogen cycle

A 
Nitrification 
Assimilation 
Denitrification 
Nitrogen fixation by organic and non-living processes
Ammonification
70
Q

What is nitrogen fixing

A

Conversion of atmospheric nitrogen (N2) into nitrogen containing compounds

71
Q

Nitrogen fixing

A

Carried out by denitrifying bacteria (Azobacter) and mtualistic bacteria (Rhizobium) in plant root nodules. Nitrogenase reduces N2 to NH3 to form amino acids
Atmospheric fixation
Haber process to make chemical fertilisers

72
Q

Atmospheric fixation

A

Converting nitrogen gas into nitrates by lightning. The energy from lightning breaks the N2 into atoms which combine w/ oxygen and dissolve in rain

73
Q

Ammonification

A

Converting nitrogen containg compounds (e.g. urea from urine) to NH3
Carried out by decomposers

74
Q

Nitrification

A

Conversion of ammonium ions to nitrites (by Nitrosomonas) and then into nitrates (by Nitrobacter) by nitrifying bacteria (chemoautotrophs)

75
Q

Assimilation

A

Nitrates in the soil are absorbed from the soil by plants and algae. Animals then eat plants and assimilate nitrogen compounds too

76
Q

Denitrification

A

Conversion of soil nitrates to atmospheric nitrogen. Carried out by denitrifying bacteria in anaerobic conditions (e.g. waterlogged soil) who use the nitrates as the final e- acceptor in respiration instead of O2

77
Q

Human activities affecting the nitrogen cycle

A

Use of fertiliser - neutrification, algae use up all the oxygen

78
Q

Processes removing atmospheric nitrogen

A

Nitrogen fixation by bacteria
Atmospheric fixation
Haber process

79
Q

Processes adding to atmospheric nitrogen

A

Denitrification

80
Q

Similarities in nitrogen and carbon cycles

A

Involves plants and animals
Involves anaerobic respiration (decomposers)
Both cycles involve atmospheric chemicals

81
Q

Differences in nitrogen and carbon cycles

A

Involves sea in cc
No fixation of CO2
Only uses organic processes in cc
N is fixed by bacteria vs on plants

82
Q

Use of transects

A

Look for changes in vegetation across a habitat

83
Q

Types of transects

A

Line

Belt

84
Q

Line transect

A

At reg. intervals

Note of which species are touching the tape

85
Q

Belt transect

A

At reg. intervals
Place a quadrat next to the line (interrupted belt transect) or move the quadrat along the line (continuous)
Used to sample succession

86
Q

Estimating pop. size

A

Mean number of a species in a quadrat/ faction of the total habitat area covered by a single quadrat

87
Q

Deciding how many samples to take

A

In a pilot study take random samples looking at species distribution
Plot quadrat number against cumulative frequency
When curve levels off use that number of quadrats

88
Q

Units to measure primary productivity on land

A

gm-2 yr-1

89
Q

Units to measure primaary productivity in water

A

gm-3 yr-1

90
Q

Decomposes in the nitrogen cycle

A

Pass urea to next stage

A-Level OCR Biology (42 decks)

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