Flashcards · Biology · Selective Breeding and Genetic Engineering
Feeding a Growing Population
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Why do crops need fertilisers?
They replace the minerals that are taken from the soil when crops are harvested.
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What does nitrate do for a plant?
It is used to make proteins and chlorophyll.
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What does a lack of nitrates cause?
Stunted growth and yellow leaves.
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What does NPK stand for?
Nitrogen, phosphorus and potassium.
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What is eutrophication?
Rapid growth of algae caused by too many nutrients, and then death of aquatic life.
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Why do fish die in eutrophication?
Bacteria use up the oxygen as they break down the dead plants and algae.
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Give one advantage of fertilisers.
Higher yield.
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Give one disadvantage of fertilisers.
Eutrophication, or the cost.
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What is biological control?
Using a living organism to control a pest.
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Give an example of biological control.
Ladybirds eating aphids, or parasitic wasps used against whitefly.
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Give an advantage of biological control.
No chemical pollution, and it is specific.
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Give a disadvantage of biological control.
It is slow and may not remove all of the pest, or the control organism may become a pest.
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What went wrong with cane toads in Australia?
They did not control the beetles, and became a pest themselves.
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Why does a graph of yield against fertiliser level out?
Other factors, such as light or water, become limiting.
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Why is a combination of methods often best?
Each method has limits, so using several reduces the problems.
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Common mistake about eutrophication?
Saying that fertiliser kills the fish directly. It is the loss of oxygen.