Biology Topic 8

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Define habitat.
The place where an organism lives.
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Define population.
All the organisms of one species in a habitat.
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Define community.
All the different species in a habitat.
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Define ecosystem.
All the organisms living in a particular area and all the non-living (abiotic) conditions, eg temperature, climate, soil-type.
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How can you estimate population sizes in different areas using a quadrat?
Place 1msquaded quadrat at a random point within the investigated area, count all organisms in quadrat. Multiply organism number by total area in m squared of the habitat. The sample may not be representative of the population, sample size-accuracy.
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How can you use quadrats to investigate the distribution of organisms?
Mark a line in the area you want to study, collect data along the line using quadrats placed next to each other.
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What are consumers?
Organisms that eat other organisms. Primary consumers are the first consumers in a food chain, and so on and so forth.
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How does a food chain work?
Start with a producer. A producer make their own food. Producers are eaten by secondary consumers, and they are eaten by tertiary consumers. Each stage is called a trophic level.
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How do pyramids of numbers work?
It shows the number of organisms at that stage of the food chain. The bottom of the food chain is at the bottom. Typically, as you go up a trophic level, the number of organisms goes down.
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How do pyramids of biomass work?
Each bar on a pyramid of biomass shows the mass of living material at that stage of the food chain. (How much all the organisms at each level would 'weigh' if you put them all together).
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Are pyramids of energy transfer always pyramid-shaped?
Yes. They show the energy transferred to each tropic level in a food chain. They're always the right shape. Pyramids of numbers aren't, and biomass are mostly.
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How is energy transferred along a food chain?
Energy from the Sun is the main source. Plants use the light energy to photosynthesise and make food. This works up the trophic levels, but each time only about 90% of energy is consumed- lost through waste, heat etc.
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Diagram of food webs showing how food chains are linked.
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How does the water cycle work?
Heat from the Sun makes water evaporate, turning it into water vapour (TRANSPIRATION), Warm water vapour is carried upwards, cools and condenses to make clouds. Water falls from the clouds as precipitation and is returned to the land and sea.
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How does the carbon cycle work?
Plants use carbon from CO2 in the air to make carbohydrates, fats and proteins. Eating passes the C compounds in the plant to animals in a food chain. Plant+animal respire, releasing CO2 into air. Die+decompose, turned into useful products- decompose
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How does the carbon cycle work? (2)
Release CO2 by respiration. Useful plant and animal products are burned (COMBUSTION). Releases CO2 into the air.
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How does the nitrogen cycle work?
Atmosphere contains 78% N2 gas. Unreactive- can't be used directly by plants. N is needed for proteins for growth- get it from soil, animals get it by eating plants.
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What is nitrogen fixation?
The process of turning N2 from the air into nitrogen compounds in the soil which plants can use. The two main ways of this happening are lightning (energy in a bolt makes N react with O2, make nitrates. N-fixing bacteria in roots and soil).
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What are the four different types of bacteria involved in the nitrogen cycle?
Decomposers- break down proteins and urea and turn them into ammonia. Nitrifying bacteria- ammonia into nitrates. N-fixing bacteria- atmospheric N into N compounds. Denitrifying bacteria- nitrates into gas.
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What is carbon monoxide?
When fossil fuels are burnt without enough air supply, this is produced. It is poisonous, and if combines with red blood cells it destroys the haemoglobin. This is mostly released in car emissions. Most modern cars have catalytic converters.
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What is a catalytic converter?
Something that turns carbon monoxide into carbon dioxide, decreasing the amount of CO that's released into the atmosphere.
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What is acid rain caused by?
Sulfur dioxide. Burning fossil fuels releases harmful gases and sulfur dioxide. When SO2 mixed with rain clouds it forms dilute sulfuric acid, making it fall as acid rain. Internal combustion engines in cars + power stations = main causes.
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Why does acid rain kill fish and tress?
Acid rain can cause a lake to become more acidic- destroying the ecosystem. Organisms are sensitive to changes in pH- can't survive. Acid damages leaves, toxic substances released, hard to absorb nutrients.
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How do greenhouse gases trap heat from the Sun?
Temperature of the Earth is a balance between the Sun and the heat it radiates back. Atmosphere absorbs it back, Re-radiated, hits back down to Earth, warms planet. Include water vapour, CO2 and methane.
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How does human activity produce lots of greenhouse gases?
Release CO2- car exhausts, industrial processes, burn fossil fuels, deforestation. Methane- rotting plants, rice growing and cattle rearing. Nitrous oxide- bacteria in soils and ocean, fertiliser, vehicle engines. CFCs - aerosol sprays, fridges.
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What is eutrophication?
Nitrates+phosphates put onto fields as mineral fertilisers, too much applied and then it rains, nitrates leached into rivers and lakes. They cause algae to grow fast+ block out light. Plants can't photosynthesise, die.
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Name another cause of eutrophication.
Pollution by sewage. It contains a lot of phosphates from detergents. Contains nitrates from urine and faeces. Cause eutrophication in the same way as fertilisers.
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How does deforestation affect the soil?
Leaching. Trees take up nutrients from soil before they can be washed away, trees are removed- don't get replaced, leaving infertile soil. Soil erosion-roots hold soil together, removed and washed away-infertile ground.
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How does deforestation disturb the water cycle?
Trees stop rainwater reaching rivers too quickly. Cut down- run straight to river, flooding. Transpiration from trees releases back into the atmosphere, cut down to make the local climate drier.
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How does deforestation disturb the balance of carbon dioxide and oxygen?
Forests take up CO2- store it in wood via photosynthesis- slowly release as decompose. Burnt- released all at once. Fewer trees= less photosynthesis, less O2 released.
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Other cards in this set

Card 2

Front

Define population.

Back

All the organisms of one species in a habitat.

Card 3

Front

Define community.

Back

Preview of the front of card 3

Card 4

Front

Define ecosystem.

Back

Preview of the front of card 4

Card 5

Front

How can you estimate population sizes in different areas using a quadrat?

Back

Preview of the front of card 5
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