Energy Flow


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Biospheres & Comparing plant and animal cells & Ph

An artificial biosphere is a structure designed to sustain life in a place which would otherwise not have life

Scientists believe that artificial biospheres on mars could be a way to colonise the planet

The biosphere would have to have: Enough photosynthesising to supply oxygen and food, recycle all waste materials, a method of keeping warm, melting martian ice.

Features of plant cells: Nucleus, cytoplasm, cell membrane, cellulose cell wall, vacuole, chloroplasts (containing chlorophyll)

Features of an animal cell: nucleus, cytoplasm and cell membrane.

Photosynthesis occurs in the chloroplasts.

CO2 + H2O > Light + chlorophyll > Glucose + Oxygen

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Absorbing mineral salts & the carbon cycle

Active transport = a plant must use energy from respraition to absorb the minerals

Carbon cycle = constant recycling of carbon
1. Photosynthesis- Co2 is removed from air
2. Respiration- Co2 is released
3. Decay- Plants and animals die, animals feed on bodies causing them to break down, releasing Co2
4. Combustion- fossil fuels are burned releasing Co2

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The nitrogen cycle

Nitrogen cycle shows how nitrogen and its compounds are recycled in nature

1. Nitrogen fixing bacteria- Converts nitrogen into nitrates (in soil)
2. Plants are eaten, nitrogen becomes animal protein
3. Dead organisms and waste contain ammonium compounds
4. Decomposers- convert urea, faeces and protein from dead organisms into nitrates in the soil
5. Nitrifying bacteria- convert ammonium compounds into nitrates in the soil
6. Denitrifying bacteria- convert nitrates into nitrogen and ammonium compounds

Nitrogen from the air is inert (unreactive)
farmers use fertilisers to replace the nitrogen in the soil
Carelessness can lead to eutrophication:
1. Nitrates cause excessive algal growth, blocking off sunlight to other plants
2. Other plants cant photosynthesise so die and rot
3. The rotting process uses up oxygen and the water cannot support life

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Food production and distribution & maximising food

Solutions to problems of unequal food distribution:
sending food from rich countries to poor ones, but the food will take a long time to arrive and will be expensive process

Teaching people to make their own food but the conditions in some countries means, crops fail

You can maximise food production using designated food production plants such as: fish farms, and large green houses

it grows in controlled environment too

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Fish farms and greenhouses

Fish farms consist of large cages suspended in lakes.

The fish grow by:
keeping eggs and young fish in tanks until they can fend for themselves, a high protein diet, keeping predators away, using chemicals to combat pests

Greenhouse conditions:
Optimum conditions for photosynthesis, plenty of water, appropriate use of pesticides and herbicides, use of fertilisers, growing plants that naturally produce large crops

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