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aqa gcse biology free > T7 organisation of an ecosystem > Flashcards

T7 organisation of an ecosystem Flashcards

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1
Q

define population

A

species that occupy the same habitat

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2
Q

define habitat

A

place in which an organism lives

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3
Q

define community

A

populations of different species interacting

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4
Q

define ecosystem

A

interactions between biotic and abiotic factors in an area

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5
Q

what do food chains show

A

feeding relationships of different organisms and the flow of energy between the organisms

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6
Q

define biomass

A

total mass of living material

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7
Q

what are trophic levels

A

stages in a food chain

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8
Q

what do arrows in a food chain represent

A

direction of biomass transfer

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9
Q

describe a simple food chain

A

producer > primary consumer > secondary consumer > tertiary consumer

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10
Q

what is a producer

A

organism that makes its own food

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11
Q

what types of organisms are primary producers

A

photosynthetic organisms like green plants and algae that trap energy from the sun

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12
Q

what is a primary consumer

A

organism that feeds on producers

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13
Q

what is a secondary consumer

A

organism that feeds on primary consumers

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14
Q

what is a tertiary consumer

A

organism that feeds on secondary consumers

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15
Q

what is a predator

A

consumer that kills and eats other animals

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16
Q

what is prey

A

animal that is killed and eaten by another animal

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17
Q

describe the pattern of predators and prey in a stable community

A

number of predators and prey rise and fall in cycles

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18
Q

why are producers the first trophic level

A

provide all biomass for the food chain (production of glucose via photosynthesis)

rest of the food chain involves the transfer of this biomass

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19
Q

piece of apparatus used to measure the abundance and distribution of organisms in an area

A

quadrat

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20
Q

piece of apparatus used to study the distribution of organisms across a gradient

A

belt transect

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21
Q

describe how materials cycle through the living and non-living components of an ecosystem

A

organisms take in elements from their surroundings

elements converted to complex molecules which become biomass

elements transferred along food chains

elements returned to environment during excretion and decomposition of dead organisms

22
Q

give 3 molecules which are cycled through ecosystems

A

oxygen
carbon dioxide
water

23
Q

describe the carbon cycle

A

plants fix CO2 into organic molecules during photosynthesis

organic carbon-containing molecules are passed onto organisms that eat the plants

CO2 is released back into the atmosphere by respiration from animals and plants

burning fossil fuels also releases CO2

24
Q

why is the carbon cycle important

A

carbon-containing molecules such as glucose are important for living organisms to grow and provide energy for vital functions within cells

25
Q

describe the water cycle

A

water from lakes and oceans evaporates

evaporated water condenses into clouds and returns to earth as precipitation

water from precipitation is useful for life on land

water then returns to rivers and oceans through surface runoff

26
Q

why is the water cycle important

A

living organisms require water and the water cycle provides organisms on land with a continuous supply of water

27
Q

why are microorganisms important for the cycling of materials through an ecosystem

A

return carbon to the environment by releasing CO2 through respiration while they decompose dead matter

decomposition of dead matter in soil returns mineral ions to the environment for other organisms to use

28
Q

what is meant by decomposition

A

breakdown of dead materials into simpler organic matter

29
Q

how do decomposers break down dead matter

A

release enzymes which catalyse the breakdown of dead material into smaller molecules

30
Q

two types of decomposition

A 
aerobic decomposition (with oxygen)
anaerobic decomposition (not w oxygen)
31
Q

what factors affect the rate of decomposition

A

oxygen availability
temperature
water content

32
Q

why is oxygen required for decomposition

A

aerobic respiration

33
Q

how does the availability of oxygen affect the rate of decomposition

A

as O2 levels increase, rate increases

as O2 levels decrease, rate decreases

34
Q

why can decomposition still occur in the absence of oxygen

A

some decomposers respire anaerobically however, rate is slower as anaerobic respiration produces less energy

35
Q

how does soil water content affect the rate of decomposition

A

decomposers require water to survive

in moist conditions, rate is high

in waterlogged soils there is little oxygen for respiration so the rate decreases

36
Q

why does decomposition require water

A

water is required for secretion of enzymes and absorption of dissolved molecules

37
Q

how does temperature affect the rate of decomposition

A

decomposers release enzymes:

rate highest at 50C

lower temp, enzymes work too slowly, rate decreases

higher temp. enzymes denature, decomposition stops

38
Q

how is the rate of change calculated when considering the decay of biological material

A

rate of change = change in value / change in time

value is a measurable variable associated with the decay of the material

39
Q

what is compost

A

nutrient-rich product of the rapid decay of waste biological material in optimum conditions set by gardeners and farmers

40
Q

how is compost used

A

natural fertiliser to promote growth of crops or garden plants

41
Q

describe how biogas generators work

A

provide methane gas for fuel through anaerobic decomposition that occurs in animal waste

42
Q

describe how environmental conditions affect communities

A

affect the abundance and distribution of organisms within communities

eg. rising global temp have been linked to extinction of frog species

43
Q

how can different temperatures be bad for certain communities

A

temp too low = growth will be slower as organisms will use more energy to stay warm

temp too high = organisms can die and water will become limited as evaporation increases

44
Q

how can change in water levels affect ecosystems

A

animals may have to migrate to find water

melting ice caps may destroy the habitats of some animals

45
Q

how can atmospheric gases affect ecosystems

A

some organisms can’t survive when certain gases are present

polluted water can cause illness to animals that drink it

46
Q

what impacts can sulfur dioxide have on the environment

A

formed when fossil fuels containing impurities are burnt

sulfur dioxide can dissolve in water to form acid rain which can erode buildings and pollute water sources

47
Q

what impacts can carbon monoxide have on the environment

A

formed from the incomplete combustion of fossil fuels

binds irreversibly to haemoglobin which prevents it from carrying oxygen

too much exposure can cause unconsciousness and death

48
Q

name 5 greenhouse gases

A 
water vapour
carbon dioxide
nitrous oxide
methane
CFCs
49
Q

give 3 human activities that contribute to greenhouse gases

A

burning fossil fuels
deforestation
large scale livestock farming

50
Q

how do greenhouse gases lead to global warming

A

allow heat from the sun to enter the atmosphere

gases act as blanket and trap the heat in the atmosphere

51
Q

3 consequences of global warming

A

sea level rise due to melting icebergs

disrupted farming and agriculture

increased spread of diseases in warmer climates

aqa gcse biology free (25 decks)

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