Energy Flow B2

Edexel course

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Biosphere... part of the Earth and its atmosphere where life exists

For Biospheres to be self containable they would have to have ;

  • enough plants to photosynthesise enough for supply of oxygen and food
  • the ability to recycle all waster materials
  • a method to keep warm
  • a method of melting Martain ice.

Plants vs Animal cells

Nucleus - Both            Cytoplasm- Both           Cell Membrane-Both                Cellulose Cell Wall- Animal doesnt   Vacuole- Animal doesnt, plant nearly always           Chloroplasts- Animal doesnt

Specialised plant cells; Xylem transport water and minerals from the roots

Phloem transport food in solution from the leaves to where it is needed, or for storage.

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make their food via photosynthesis. (meaning making through light) It occurs in the chloroplasts of many cells of green plants that are exposed to light.


Temperature- as it rises so does photosynthesis; if it exceeds 37C enzymes are destroyed.

Carbon dioxide concentration- as it rises so does photosynthesis;

Light intensity- as it inreases so does photosynthesis.

Uses of plants- food; decorations; building materials

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Absorbing mineral salts...

...plants absorb salts (magnesium, nitrogen, pottassium and phosphrous) from the soil by osmosis. (salts are sometimes called ions/mineral ions)

active transport-plants absorb minerals against a concentration gradient (from low to high)

Plants need nitrogen for healthy growth but they cannot use the nitrogen from the air because it is inhert (unreactive). Fertilisers are used to replace the nitrogen. This means crop yields can be increased. Careless behaviour can lead to Eutrophication.

Eutrophication-the excessive growth and decay of aquatic plants due to increased levels of nutrients in the water which results in oxygen levels dropping so organisms eg fish die.

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The Carbon Cycle...

is the process of carbon being recycled between living organisms and the environment...

1.Photosynthesis carbon dioxide is removed from the atmosphere to produce glucose. some is returned to the air during respiration.

2.Resperation-plants and animals respire releasing soem carbon dioxide into the atmosphere,

3.Decay-when plants and animals die other organisms feed on them cauing them to break down releasing carbon dioxide into the air. Microorganisms eating dcay release carbon dioxide when they respire.

4.Combustion- fossil fuels release carbon dioxide when burned.

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The Nitrogen Cycle..

1. Nitrogen fixing bacteria-convert atmospheric nitrogen into nitrates in soil.

2. When plants are eaten the nitrogen becomes animal protein

3.Dead organisms and waste contain ammounium compounds

4.Decomposers - convert urea, faeces and protein from dead organisms into ammonium compounds.

5.Nitrifying bacteria-convert ammonium compounds into nitrates in the soil.

6.Denitrifying bacteria-convert nitrates into atmospgeric nitrogen and ammounium compounds.

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