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A-level Biology > 6.23 - Ecosystems > Flashcards

6.23 - Ecosystems Flashcards

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1
Q

ecosystem

A

made up of all the living organisms that interact with one another in a defined area (varying in size)and the physical factors present in that region

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2
Q

habitat

A

A place where organisms live, where all of their needs can be met

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3
Q

biodiversity

A

the variety of living organisms within an area

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4
Q

population

A

all of the individuals of a species in a given area/habitat

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5
Q

community

A

all of the species in an area/habitat

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6
Q

intraspecific

A

within a species

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7
Q

interspecific

A

between species

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8
Q

the effect of light availability on plants

A
  • the greater the availability of light, the greater the success of plants as light is required for photosynthesis
  • plants can develop strategies to cope with different light intensities (e.g. larger leaves, different photosynthetic pigments)
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9
Q

the effect of light availability on animals

A
  • low availabilities of light affect the whole animal food chain due to being indirectly affected by a lack of plants
  • affects cell mutation (vitamin D)
  • influences metabolic rate so affects movement and reproduction
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10
Q

the effect of temperature on plants

A
  • affects enzymes controlling metabolic reactions
  • plants will develop more rapidly in warmer temperatures
  • changes in temperature can trigger leaf abscission, dormancy and flowering
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11
Q

the effect of temperature on animals

A
  • affects enzymes controlling metabolic reactions
  • ectothermic animals will develop more rapidly in warmer temperatures
  • changes in temperature can trigger migration and hibernation
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12
Q

effect of water availability on plants

A
  • severe water stress can lead to death
  • lack of water will cause most plants to wilt
  • water is required for photosynthesis
  • waterlogged soil can lead to a lack of oxygen availability
  • xerophytes adapted to low levels of water
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13
Q

effect of water availability on animals

A
  • severe water stress can lead to death
  • water stress can trigger migration
  • aquatic organisms will die or migrate if habitats dry out
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14
Q

effects of oxygen availability on plants

A
  • waterlogged soils affects aerobic respiration and active transport as air spaces between the soil particles are saturated with water
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15
Q

effects of oxygen availability on aquatic animals

A
  • water becoming too warm or flow rate too slow can lead to a drop in oxygen concentration, suffocating aquatic organisms
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16
Q

clay soil

A
  • fine particles
  • easily waterlogged
  • forms clumps when wet
  • fewer plants can survive in waterlogged soil due to reduction in aerobic respiration
  • roses, geraniums, earthworms, nematodes, microbes
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17
Q

loam soil

A
  • different sized particles
  • retains water but does not become waterlogged
  • ideal conditions for plants as sufficient water and sufficient ai spaces
  • high levels of minerals and decaying matter
  • wisteria, delphinium, earthworms, nematodes, microbes
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18
Q

sandy soil

A
  • coarse, well-separated particles that allow for free draining
  • does not retain water
  • easily eroded
  • does not retain water well enough for many plants to survive
  • low levels of minerals, acidic
  • plants adapted to retain moisture with large root systems such as cacti and lavender
  • termites, nematodes, microbes
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19
Q

converts trophic levels

A
  • each stage in the food chain
  • producer = an organism that converts light energy into chemical energy through photosynthesis
  • consumers = organisms that obtain their energy by feeding on other organisms
  • food chains rarely have more trophic levels after a quaternary consumer as there is not sufficient biomass and stored energy left to support any further organisms
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20
Q

calculating net biomass production

A

gross production - respiratory losses

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21
Q

calculating ecological efficiency

A

biomass transferred to next trophic level / biomass available at previous trophic level X100

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22
Q

efficiency at producer level

A
  • only convert 1-3% of sunlight they receive into chemical energy and therefore biomass
  • not all solar energy is available for photosynthesis, a lot of it is reflected, transmitted through the leaf or a unusable wavelength
  • other factors may be a limiting factor to photosynthesis such as water availability
  • a proportion of energy is ‘lost’ as it is used for photosynthetic reactions
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23
Q

efficiency at consumer levels

A
  • convert at most 10% of biomass in food to organic tissue
  • not all biomass of an organism is eaten
  • some energy is transferred to the environment as metabolic heat from movement or respiration
  • some parts of an organism are eaten but indigestible, so energy content is egested as faeces
  • some energy lost in excretory materials
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24
Q

how can human activities manipulate biomass through ecosystems

A

Agriculture
- provided with required abiotic factors
- competition and predators removed
- creates very simple food chains, so fewer trophic levels so as much energy as possible is transferred to humans

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25
Q

Fencing

A
  • use of structures to separate and contain animals and crops
  • reduces loss to predators and pests, increasing yield and therefore biomass available to humans
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26
Q

greenhouses

A
  • artificial environment for growing plant crops
  • abiotic needs of plants are met, increasing biomass production
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27
Q

pesticides and herbicides

A
  • use of chemicals to kill insect herbivores and weeds
  • biomass losses to insect consumers and competition are reduced, increasing yield and available biomass
28
Q

stabling

A
  • animals are sheltered indoors and provided with food
  • reduces energy movement through maintenance of temperature and restricted movement, reduced biomass lost through respiration
29
Q

food chain management

A
  • agricultural food chains restricted typically to 2or 3 trophic levels
  • minimises energy/biomass lost at each trophic level, so more available to human consumers
30
Q

decomposers

A
  • an organism that feeds on and breaks down dead plant or animal matter
  • turns organic compounds into inorganic ones (nutrients) available to photosynthetic producers in the ecosystem
  • primarily microscopic fungi and bacteria, but also larger fungi such as toadstools
  • saprotrophs because they obtain their energy from dead or waster organic material
  • digest food externally by releasing enzymes which break down complex organic molecules into simpler soluble molecules
31
Q

detritivores

A
  • help to speed up the decay process by feeding on detritus (dead and decaying material)
  • break detritus down into smaller pieces of organic material which increases the surface area for decomposers to work on
  • perform internal digestion
  • e.g. woodlice, earthworms, maggots
32
Q

Recycling nitrogen

A
  • essential element for making amino acids and nucleic acids in plants and animals
  • animals obtain nitrogen from the food they eat, but plants need to take in nitrogen from their environment
  • nitrogen is abundant in the atmosphere, but plants cannot take up nitrogen gas
  • bacteria play a very important role in converting nitrogen into a form useable to plants
33
Q

nitrogen fixation

A
  • nitrogen fixing bacteria (e.g. azobacter and rhizobium)
  • contain nitrogenase
  • combines atmospheric nitrogen with hydrogen to produce ammonia (NH3)
  • other bacteria convert the ammonia into other organic compounds that can be absorbed and used by plants
  • some are free living soil bacteria (Azobacter)
  • come live inside root nodules (Rhizobium) of leguminous plants (plants gain amino acids, bacteria gains carbohydrates)
34
Q

nitrification

A
  • ammonium compounds in the soil are converted into nitrogen containing molecules that can be used by plants
  • oxidation reaction, so only occurs in well aerated soil
  • nitrifying bacteria (e.g. nitrosomonas) oxidise ammonium compounds into nitrites (NO2-)
  • nitrobacter oxidise nitrites into nitrates (NO3-)
  • nitrate ions are highly soluble so is how most nitrogen enters a plant
35
Q

denitrification

A
  • in the absence of water( (waterlogged soils) denitrifying bacteria convert nitrates in the soil back into nitrogen gas
  • under anaerobic conditions
  • bacteria use nitrates as a source of energy for respiration and nitrogen gas is released
36
Q

ammonification

A
  • decomposers convert nitrogen containing molecules in dead organisms and waste products into ammonium compounds
37
Q

nitrogen cycle

A
  • nitrogen gas in atmosphere into ammonia in soil through nitrogen fixation by bacteria and ammonification by decomposers
  • nitrification of ammonia into nitrites then nitrates by nitrifying bacteria
    (denitrification by anaerobic bacteria)
  • uptake and assimilation by plants
  • plant protein eaten by animals and converted into animal proteins
  • death, decay
  • nitrogen fixation by non-living processes
38
Q

processes involved in the carbon cycle

A
  • photosynthesis
  • respiration
  • combustion
  • feeding
  • death
  • decomposition
39
Q

Main processes in the carbon cycle

A
  • carbon stored in producers in the form of macromolecules (e.g. proteins, lipids) converted through photosynthesis
  • passes up food chain when eaten
  • carbon compounds in dead organisms released by decomposers
  • carbon released as CO2 into the atmosphere through respiration and combustion of fossil fuels
  • if decomposition is prevent (e.g. in peat bogs or ocean floors) carbon is ‘trapped’ and remains form fossil fuels
40
Q

succession

A

the progressive replacement of one dominant type of species or community by another in an ecosystem until a stable climax community is formed

41
Q

primary succession

A

occurs on an area of land that has been newly formed or exposed such as bare rock. There is no soil or organic material present to begin with

42
Q

secondary succession

A

occurs on areas of land where soil is present, but contains no plant or animal species e.g. bare earth remaining after a forest fire

43
Q

deflected succession

A
  • human activities can halt natural flow of succession and prevent the ecosystem from reaching a climax community
  • agriculture is one of the main reasons deflected succession occurs
  • trampling and grazing by domesticated animals means large areas of land remains grassland
  • removing existing vegetation to plant crops means crops become final community
  • burning as a means of forest clearing increases biodiversity as it provides space and nutrient-rich ash for other species such as shrubs to grow
44
Q

plagioclimax

A

the final stage formed when succession is stopped artificially

45
Q

characteristics of a pioneer community

A
  • colonisers e.g. lichen
  • hostile conditions
  • low species diversity
  • instability
46
Q

characteristics of a climax community

A
  • dominant species e.g. woodland
  • less hostile conditions
  • high species diversity
  • stability
47
Q

long term and short term fluctuations in atmospheric carbon dioxide

A

Short term:
- fluctuate through the day as photosynthesis only occurs during the day, removing CO2 from the atmosphere, so CO” levels are higher at night
- CO2 levels are lower in summer than winter as photosynthesis rates are higher
Long term:
Increased significantly due to:
- combustion of fossil fuels
- deforestation

48
Q

when does primary succession occur

A
  • after volcanic eruptions, when deposited lava cools and solidifies, creating igneous rock
  • sand is blown by the wind or deposited by the sea to create new sand dunes
  • silt and mud are deposited at river estuaries
  • glaciers retreat, depositing rubble and exposing rock
49
Q

main seral stages

A
  • pioneer community
  • intermediate community
  • climax community
50
Q

the process of succession

A

(pioneer community)
- bare rock/ barren land
- colonisers like lichen carried by wind or in animal droppings start to break down bare rock
(intermediate community)
- weathering of bare rock provides particles that form the basis of soil
- contains nutrients and retains water so supports secondary colonisers e.g. mosses
- may provide food for animal species
- decay creates a layer of humus
- followed by tertiary colonisers e.g. ferns
- abiotic conditions increasingly favour grasses, shrubs and then small trees
(climax community)
- a few dominant plant and animal species e.g. woodland
- stable state
- climate determines dominant species
- biodiversity decreases as dominant species outcompetes others
-

51
Q

adaptations of organisms in the pioneer community

A
  • the ability to produce large numbers of seeds or spores which are blown by the wind and deposited on new land
  • seeds that germinate rapidly
  • ability to photosynthesise
  • tolerance of extreme environments
  • ability to fix nitrogen from the atmosphere, adding to soil minerals
52
Q

adaptations of organisms in the intermediate community

A
  • tolerance of low water and mineral environments
  • waxy cuticle to prevent water loss
  • at each stage, species are better adapted, outcompeting others
53
Q

adaptations of organisms in the climax community

A

Temperate climates
- trees dominant as mild temperatures and abundant water
Subarctic conditions:
- herbs or shrubs dominant as temperature and water availability is low

54
Q

Animal succession

A
  • similar to plant succession but lower as they have to move in from neighbouring areas and new land is often geographicallty isolated
  • primary colonisers such as insects and worms consume and shelter in mosses and lichens present
  • secondary colonisers such as ammals and reptiles will arrive when conditions are suitable e.g. suitable food source and sufficient plant cover
55
Q

distribution

A
  • where individual organisms are found within an ecosystem
  • usually even throughout an ecosystem as organisms are generally found where abiotic and biotic factors favour them
  • usually measured using a belt or line transect
56
Q

abundance

A
  • the number of individuals of a species present in an area at any given time
  • may fluctuate daily
  • immigration and births will increase the number, emigration and death will decrease the number
  • usually estimated through sampling techniques
57
Q

measuring pant abundance

A
  • quadrats are placed randomly in an area
    estimated number in population (per m²) = number of individuals in a sample / area of sample (m²)
58
Q

measuring animal abundance

A
  • capture-mark-release-recapture method used to estimate population sizes of animals that are mobile
  • capture as many individuals as possible in a sample area
  • mark or tag each individual
  • release marked animals back into the sample area and allow time for them to redistribute themselves throughout the habitat
  • recapture as many individuals as possible in the original sample area
  • record the numbers of marked and unmarked individuals present in the sample
  • release all individuals back into their habitat
  • use the Lincoln index to estimate population size
    Estimated population size = (number of individuals in first sample * number of individuals in second sample) / number of recaptured marked individuals
59
Q

Lincoln index

A

Estimated population size = (number of individuals in first sample * number of individuals in second sample) / number of recaptured marked individuals

60
Q

Simpson’s index of diversity

A

always results in a value between 0 and where 0 represents no diversity and 1 represents infinite diversity. the higher the value the more diverse the habitat

61
Q

Quadrats

A

Used to measure how common organisms are in a sample area or to compare how common organisms are in different sample areas
- area to be sampled divided into a grid
- random number generator used to pick coordinates of sample area
- quadrat (frame enclosing known area) placed in coordinate
- organisms in quadrat counted
- repeat procedure and calculate mean
- can sample additional areas to compare effect or factors such as sunny vs shaded

62
Q

transect

A

used to study how distribution of organisms change across an area
- line marked out in the sample area
- either count organisms that touch the line or place quadrats across the line at set intervals and count the organisms
- repeat procedure and calculate mean

63
Q

pitfall trap

A

Sample insects etc. living on the ground
- hole or container dug into ground with steep sides
- covered to keep out rain and predators
- insects fall and cannot escape

64
Q

pooter

A

Sample and identify individual insects
- container with two tubes, one covered with mesh
- covered tube is sucked which draws air and insects into the container

65
Q

beating net/tray

A

Sample insects living in trees/bushes
- net/tray held underneath tree/bush
- foliage is shaken, insects fall onto net/tray

66
Q

sweep net

A

Sample insects living in long grass, rivers etc.
- fine net with long handle to be used in a sweeping motion to capture insects

A-level Biology (24 decks)

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