UNIT 3 - Photosynthesis And Food Production
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What are the two stages of photosyntheses?
-Light reactions -Carbon fixation
Where does photosynthesis take place?
Chloroplasts
What are the 2 uses of the energy absorbed by chlorophyll?
1)used too split water 2)convert chemical energy to ATP
What is the raw material for light reactions?
Water
What 2 substances formed during the light reactions are needed for carbon fixation?
Hydrogen and ATP
What happens to the oxygen produced by light reactions?
It diffuses out of the leaf
What is photosynthesis?
A series of enzyme controlled reactions. Chloroplasts trap light energy which split water and is also converted into chemical energy in the form of ATP
What is the gas in the air that joins with ATP and hydrogen from the light reactions?
Carbon dioxide
What is the product of carbon fixation?
Sugar
What is photosynthesis controlled by?
Enzymes
What are the uses of the sugar produced by photosynthesis?
-starch for storage -cellulose for structure -respiration
What are the limiting factors in photosynthesis?
-temperature -carbon dioxide concentration -light intensity
How do nitrates work?
The nitrates dissolve in the soil water and are then absorbed by the plants roots.
What are nitrates used for?
Nitrates are used to produce amino acids which are synthesised into plant protein
What happens as pesticides are passed along the food chain?
The toxicity levels increase
What is a problem with fertilisers?
1)Fertilisers that are sprayed onto crops can leach into the freshwater (of rivers, lochs, and ponds) adding extra, unwanted nitrates. 2)This fertiliser greatly increases the growth of algae in the water. This will increase algal populations causing algal blooms. 3)Algal blooms reduce light levels. This means the plants can’t photosynthesise and so they die. 4)These dead plants, as well as dead animals become food for bacteria which greatly increase in number. 5)These bacteria use up large quantities of oxygen, which means there is less oxygen for the other organisms living in the fresh water-this can cause them to die
What is an alternative to pesticides and fertilisers?
-GM crops. This involves taking useful gene from one organism and inserting it into another. -Biological Control. This involves using animals that are natural predators to try and keep the number of pests down.
What is an indicator species?
A species whose presence or absence can show the conditions of the environment/level of pollution in the area
What is the build up of toxic substances in living organisms known as?
Bioaccumulation