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

Unit 6 - Ecosystems Flashcards

1
Q

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
How is biomass lost
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)
26
Loss of biomass in endotherms vs ectotherms
Ectotherms use less energy in maintaing body heat so there is more biomass availabe
27
Saprotrophs
Secrete extracellular enzymes onto dead/waste materials | Digest the materials into small molecules which are then absorbed and stored/respired
28
Why is the producer efficiency v. low
Approx 90% of light is reflected, unusable wavelength and transmitted through leaf Limiting factors Energy used for photosynthetic reactions
29
Succession
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
30
Climax community
Final, stable community that exists after the process of succession has occurred Usually woodland communities
31
Deflected succession
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
32
Pioneer species
Species that begin the process of succession, often colonising an area as the first living thing there
33
Primary succession
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
34
Secondary succession
Does not start from bare ground | Takes place on a previously colonised but damaged/disturbed habitat
35
Why are sand dunes helpful in terms of succession
Shows us the stages of succession in order of occurrence whereas usually we only see the current stage
36
How does succession affect species diversity
Increases it however dominant species may outcompete the smaller species killing whole species off
37
Weathering
Breakdown or decomposition of rock in situ
38
How does weathering contribute to succession
Decomposition of rock increases soil depth/ changes soil composition Favouring new species
39
Calculating net primary production
Gross primary production = npp - products of respiration
40
Calculating efficiency of energy transfer
Net production/ food intake x 100
41
Plagioclimax
Sub-climax community when succession has been deflected
42
Ways to deflect succession
``` Mainly agriculture and human activity e.g. Grazing Burning Application of fetilisers Application to herbicide Exposure to excessive amounts of wind ```
43
How does succession affect biomass
Increases it due to more organisms in the ecosystem
44
Why should sub-climax communities be conserved
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
Pioneer species on sand dunes
Species that can tolerate salty water, lack of fresh water and stable sand e.g. sea rcket
46
Pioneer species on bare rock
Algae and lichens as they don't need to be anchored into the soil
47
Increasing primary productivity
``` Some crops are planted early Irrigating crops Drought resistant crops Using greenhouses Crop rotation Fertilisers (provides inorganic ions) Pesticides/ pest resistant crops ```
48
How does planting some crops early increase primary productivity
Provides a longer growing season to harvest more light
49
How does irrigating crops increase primary productiviy
Water is readily available for the light dependent stage of photosynthesis even when rainfall is below average
50
How does growing crops in a greenhouse increases primary productivity
Provides a warmer temp ---> increases the rate of photosynthesis
51
How does crop rotation increase primary productivity
Stops reduction in soil levels of inorganic ions e.g. K^+ or NO3^-
52
Crop rotation
Growing a diff. crop in each field on a rotational cycle
53
How does use of pesticides increase primary productibity
Prevents loss of biomass and lowering yield of plant
54
Why do plants need NH4+
Maintains pH
55
Why do plants need NO3-
Part of the nitrogen cycle
56
Function of K+ in plants
Improves growth of leaves
57
Function of PO4 3- in pants
Improves growth of roots
58
Increasing secondary productivity
``` Harvesting animals before adulthood Selctive breeding Animals treated w/ antibiotics Zero grazing Keeping environmental temp constant - prevents energy loss through homeostasis ```
59
How does harvesting animals before adulthood increase secondary productivity
Minimises loss of energy as younger animals invest a larger proportion of energy into their growth
60
How does selective breeding increase secondary productivity
Produces improved animal breeds w/ faster growth, increased egg production and increased milk production
61
Zero grazing
Bringing food directly to animals | Maximises energy allocated to developing muscle by reducing need to move
62
Processes in the carbon cycle
``` Photosynthesis Respiration (animals and plants) Anaerobic respiration (dead organic matter and excreta) Fossilisation Combustion Diffusion and carbonic acid formation Diffusion Decomposition Feeding Sedimentation ```
63
Processes adding to atmospheric CO2
Respiration Combustion Diffusion frm the sea to the air
64
Processes removing atmospheric CO2
Photosynthesis | Diffusion and carbonic acid formation in the ocean
65
Sedimentation
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
Fossilisation
Organic matter is buried and copressed over millions of years forming gas, coal and oil
67
Human interferences that affect the carbon cycle
Combustion Population size (respiration and waste) Deforestation Farming
68
Effects of human interences w/ the carbon cycle
``` 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
Processes in the nitrogen cycle
``` Nitrification Assimilation Denitrification Nitrogen fixation by organic and non-living processes Ammonification ```
70
What is nitrogen fixing
Conversion of atmospheric nitrogen (N2) into nitrogen containing compounds
71
Nitrogen fixing
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
Atmospheric fixation
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
Ammonification
Converting nitrogen containg compounds (e.g. urea from urine) to NH3 Carried out by decomposers
74
Nitrification
Conversion of ammonium ions to nitrites (by Nitrosomonas) and then into nitrates (by Nitrobacter) by nitrifying bacteria (chemoautotrophs)
75
Assimilation
Nitrates in the soil are absorbed from the soil by plants and algae. Animals then eat plants and assimilate nitrogen compounds too
76
Denitrification
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
Human activities affecting the nitrogen cycle
Use of fertiliser - neutrification, algae use up all the oxygen
78
Processes removing atmospheric nitrogen
Nitrogen fixation by bacteria Atmospheric fixation Haber process
79
Processes adding to atmospheric nitrogen
Denitrification
80
Similarities in nitrogen and carbon cycles
Involves plants and animals Involves anaerobic respiration (decomposers) Both cycles involve atmospheric chemicals
81
Differences in nitrogen and carbon cycles
Involves sea in cc No fixation of CO2 Only uses organic processes in cc N is fixed by bacteria vs on plants
82
Use of transects
Look for changes in vegetation across a habitat
83
Types of transects
Line | Belt
84
Line transect
At reg. intervals | Note of which species are touching the tape
85
Belt transect
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
Estimating pop. size
Mean number of a species in a quadrat/ faction of the total habitat area covered by a single quadrat
87
Deciding how many samples to take
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
Units to measure primary productivity on land
gm-2 yr-1
89
Units to measure primaary productivity in water
gm-3 yr-1
90
Decomposes in the nitrogen cycle
Pass urea to next stage

LGS A-Level OCR Biology (42 decks)

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