Biology Paper 2: Topic 9 - Ecosystems - Flashcards in GCSE Biology

What are the four levels of organisation in an ecosystem?

1) Individual
2) Population - All organisms of the same species living together in a habitat
3) Community - All of the populations of different species living in a habitat
4) Ecosystem - The community of organisms and abiotic components of an area and how

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1) What are abiotic factors?
2) What are some examples of them?

1) Non-living aspects of an ecosystem
2) Water availability, light levels, temperature, pollutants

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How can communities be affected by environmental conditions?

Temperature, light and water availability affect the abundance and distribution of organisms within communities
e.g. light intensity affects rate of photosynthesis of producers which in turn affects consumers

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How can communities be affected by pollutants?

Toxic chemicals bioaccumulate in food chains which becomes deadly for tertiary and quaternary consumers
Fertilisers can cause eutrophication.
Air pollution can kill plants

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1) What are biotic factors?
2) Give examples

1) Living components of an ecosystem
2) predation, competition

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How does competition affect communities?

The presence of competitors affects population distribution and size
Better adapted species in a certain environment outcompete other species causing those less adapted to die off

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How does predation affect communities?

Predation affects prey populations within communities. The higher number of predators, the less prey and the opposite is also true.
Many of the other organisms within the food chain will also be affected

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1) What does interdependence mean?
2) Give some examples

1) Organisms rely on each other. A change of population in one species affects another population within a community
2) Plants relying on pollinators, herbivores depending on plants.

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What is mutualism?

The interaction between two organisms where both benefit as a result of their relationship?

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What is parasitism?

The interaction between two species where only one benefits. The parasite gains whilst the host is harmed.

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What apparatus is used to measure abundance of organisms in an area?

A quadrat

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What apparatus is used to measure abundance and distribution of organisms along a gradient?

A belt transect

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What is the equation for biomass transfer between trophic levels?

Efficiency =
((Biomass available after transfer) / biomass available before transfer)) x 100

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What is biodiversity?

The variety of living organisms in an ecosystem

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How does fish farming affect biodiversity?

Parasites and diseases within the fish farm can spread outside the farm and harm wildlife
Wildlife can become tangled in the net
Waste from the farm and food for the farm fish can cause eutrophication

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How does eutrophication affect biodiversity?

Excess fertiliser running into rivers and lakes causes algal blooms to block sunlight from aquatic plants so they can't photosynthesise and die. when the algae themselves die, decomposers further reduce oxygen levels. Animals fail to respire and die.

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How do non-indigenous species affect biodiversity?

They may out-compete indigenous species for a certain resource so the indigenous species die
The indigenous species can become prey
The non-indigenous species can bring diseases which the indigenous species haven't developed immunity to

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How can humans positively impact biodiversity?

Conservation schemes, breeding endangered species, reforestation, minimising global greenhouse production

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How do we benefit from maintaining biodiversity?

Provides jobs for ecotourism, conservation schemes and reforestation.
We may discover a plant species with a chemical that can be used in future medicine
Less damage to food chains means we can meet future food requirements

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What are the biological factors affecting food security?

- Growing population: demand for food grows
- New pests and pathogens: destroys crop yields or livestock
- Environmental change:
- Changing diets: more energy and biomass available from eating plants
- Sustainability:

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What are the main material cycles?

- Water cycle
- Carbon cycle
- Nitrogen cycle

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How do materials cycle through the biotic and abiotic components of an ecosystem?

- Organisms take in elements from their surroundings
- The elements are converted to complex molecules, becoming biomass
- The biomass is transferred along food chains
- During excretion and decomposition, the elements return to the environment

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How can potable water be obtained?

- Reverse osmosis
- Thermal desalination - evaporating water which leaves the salts behind

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What do plants need to make proteins?

Nitrates

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Describe the stages of the nitrogen cycle

- Lightning and nitrogen-fixing bacteria in soil and root nodules of legumes convert nitrogen gas into ammonia to be dissolved into ammonium ions
- Nitrifying bacteria converts the ammonium ions into nitrate ions to be absorbed by plants to build proteins

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(Nitrogen cycle continued)

- Due to feeding, nitrogen passes through food chains
- Decomposers break down urea and proteins to form ammonia which dissolves to form ammonium ions
- Denitrifying bacteria in waterlogged soil convert nitrate ions in the soil to form back into nitrogen

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How can the amount of nitrates in the soil be increased?

- Fertilisers: manure, compost or artificial NPK fertilisers
- Crop rotations: planting a nitrogen fixing crop

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What is an indicator species?

A species whose presence or absence can provide information on an environmental condition e.g. pollution levels

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1) What indicator species can be used to identify polluted water?
2) Why?

1) Bloodworms, sludgeworms
2) They are adapted to live in polluted water

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1) What species can be used to identify clean water?
2) Why?

1) Stonefly, freshwater shrimp
2) They are sensitive to oxygen concentration and so can only live in clean water

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1) What indicator species can be used to identify clean air?
2) Why?

1) Blackspot fungi on rose leaves, certain lichen (depending on their adaptation)
2) They are sensitive to sulphur dioxide concentrations and so can only live in clean air

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Evaluate the use of indicator species for measuring pollution

FOR: They are cheaper and simpler, they can be used to monitor conditions over long periods of time
AGAINST: They are less accurate than electronic monitors, they do not provide a quantitative result for how bad the pollution is

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What factors affect decomposition rate in food?

- Oxygen availability: needed for respiration in decomposers
- Temperature: decomposers' enzyme activity
- Water content: decomposers need water to live

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How can we preserve food and how do they do it?

- Fridge/freezer: slows microbes' enzyme reactions
- Salt: loss of water through osmosis
- Drying: lack of water means microbes struggle to live
- Airtight cans: Microbes can't enter

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What the optimum conditions for making compost?

- Warm (but not too high) temperature
- Plentiful supply of oxygen
- Moist

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What is the equation for decomposition rate?

Decomp. rate = mass lost/time

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Biology Paper 2: Topic 9 - Ecosystems

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