Flashcards · Biology · Feeding the Human Race
Agricultural Solutions to the Demands of the Growing Population
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Which three minerals are in an NPK fertiliser?
Nitrate, phosphate and potassium.
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Why do crops need nitrate?
To make amino acids and then proteins for growth.
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Give one advantage of using fertilisers.
They raise the yield, so more food is produced from the same land.
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What is eutrophication?
Too many mineral ions in water, which causes an algal bloom and then a loss of oxygen.
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Why do fish die in a eutrophic lake?
Bacteria use up the oxygen when they break down the dead plants, so the fish suffocate.
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What is a herbicide?
A pesticide that kills weeds.
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Why can pesticides harm food chains?
Some are not broken down and build up in the bodies of animals along the chain, and they kill harmless insects as well.
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Why may a pesticide stop working?
Pests with resistance survive, breed and pass on the resistance.
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What is hydroponics?
Growing plants with their roots in a nutrient solution instead of soil.
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Why is air bubbled through a hydroponics tank?
So that the roots have oxygen for respiration.
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Give two advantages of hydroponics.
Exact control of minerals and conditions, high yields, and crops can be grown where the soil is poor.
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Give two disadvantages of hydroponics.
It is expensive to set up and run, and a failure or infection can lose the whole crop.
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What is biological control?
Using living organisms, such as predators, to reduce the numbers of a pest.
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Name a predator used to control aphids.
The ladybird, or its larvae.
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Give one problem with biological control.
It is slow, it will not remove the pest completely, or the control species may harm other organisms.
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What went wrong when cane toads were released in Australia?
They did not control the beetles, but they bred, spread and poisoned native predators.
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What does the Bt gene do in a crop?
It makes the crop produce a protein that kills the caterpillars that eat it.
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Label the parts of this hydroponics set-up and say what each one does. 
The support holds the plants up. The roots take mineral ions from the nutrient solution. The air pump bubbles air through the solution so that the roots get oxygen for respiration. Light is needed for photosynthesis.
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Name the parts of the hydroponics set-up marked A, B and C. A is the roots. B is the nutrient solution (water with mineral ions). C is the air pump.