Biology B3b revision summary

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Revision summary ­ B3b
The world's population is currently rising very quickly, and it's not slowing down. This mostly due to
modern medicine and farming methods, which have reduced the number of people dying from
disease and hunger.
Three ways in which a rising population is affecting the environment:
1. It puts pressure on the environment, as we take the resources we need to survive.
2. People around the world are also demanding a higher standard of living, which we use
more energy for the manufacturing process. This means we're taking more and more
resources more and more and more quickly.
3. Raw materials are being used up faster than they are being replaced, so eventually we will
run out.
Four main activities that use up land:
1. Building
2. Farming
3. Dumping waste
4. Quarrying for metal ores.
Five important stores of carbon:
1. Carbon is present in the atmosphere as carbon dioxide.
2. Many processes lead to CO2 being released, e.g. burning fossil fuels.
3. Too much CO2 in the atmosphere causes global warming.
4. The CO2 can be sequestered (locked up) in natural stores, including:
Oceans, lakes and ponds.
Green plants, where it's stored as carbon compounds. Green plants remove CO2
from the atmosphere during photosynthesis.
Peat bogs
5. Storing CO2 in these ways is really important because it means CO2 is removed from the
atmosphere.
It's important to have stores of carbon because it traps heat from the sun. The levels of carbon
dioxide (a greenhouse gas) are rising quite sharply, which is gradually heating up the Earth.
Two important greenhouse gases are carbon dioxide and methane. They are called `greenhouse
gases' because they help keep heat in, in the atmosphere.
Three reasons why people chop
down large areas of forest:

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To provide timber to use as building material
2) To clear more land for farming, which is important to:
Provide more food, e.g. from more rice fields or farming cattle,
Or, grow crops from which bio fuels based on ethanol can be produced
3) To produce paper from wood.
Biodiversity is the variety of different species in a habitat ­ the more species the greater the
biodiversity.…read more

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Fungus is the main source of Mycoprotein. A fungus called Fusarium is the main source. It's grown in
fermenters, using glucose syrup as food. The glucose syrup is obtained by digesting maize starch
with enzymes. The fungus respires aerobically, so oxygen is supplied, together with nitrogen (as
ammonia) and other minerals. It's important to prevent other organisms growing into the
fermenter, so it's initially sterilised using steam. The incoming nutrients are heat sterilised and the
air supply is filtered.…read more

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