3.5 Food Production

Why do humans need to increase food yields?

Increasing human population.

Where in the world is the highest rate of population increase?

Developing countries.

What do we call the practice of maximising food yields?

Intensive farming methods.

Why do intensive farming practices work?

Increase energy transfer to the consumer due to pests being removed.

What chemicals are involved in intensive farming methods?

Fertilisers and pesticides.

What is a monoculture?

One species grown over a large area.

What are the advantages of monoculture?

Crop is suitable for climatic conditions, more machinery can be used reducing labour costs, and more than one harvest per year.

What are the disadvantages of monocultures?

More fertilisers used, compaction by machinery reduces oxygen concentration in soil, and removal of hedgerows reduces habitats for animals.

What is a fertiliser?

A substance added to soil with chemicals required for plant growth.

What are pesticides?

Chemicals added to crops to kill plants or animals that reduce plant growth.

Name a chemical found in fertilisers.

Nitrates.

Why are nitrates needed by plants?

Needed to make amino acids, proteins and nucleic acids.

Why is magnesium needed by plants?

To make chlorophyll.

Give a requirement of fertilisers that allows them to be taken up by plants.

Soluble.

What is the disadvantage of fertilisers being soluble?

They leach out of the soil in rain into rivers.

What does an increase in the level of nitrates in water lead to?

Algal bloom.

What effect does an algal bloom have on a freshwater ecosystem?

Reduces light to plants, plants die and decompose, and oxygen levels in water decrease.

What can reduce the use of pesticides?

Gm crops.

What kind of pesticide kills weeds?

Herbicide.

What kind of pesticide kills fungi?

Fungicide.

What kind of pesticide kills insects?

Insecticide.

What kind of pesticide kills bacteria?

Bactericides.

What is a disadvantage of pesticides?

Accumulate in the bodies of organisms.

What is bioaccumulation?

The levels of pesticide in the bodies of organisms increase at each trophic level in a food chain.

Give an example of a problematic pesticide?

Ddt.

What is most affected in a food chain by the use of pesticides like ddt?

Top predator.

What effects does ddt have on predatory birds?

Thinning of egg shells so chicks hatch before they are strong enough to survive.

What are alternatives to the use of pesticides?

Gm crops and biological control.

What is biological control?

Making use of predators or parasites to control the population of pest species.

Give a disadvantage of the use of insecticides?

The killing of advantageous insects like pollinators.

When is biological control most effective?

In small enclosed areas where the predator cannot leave the area.

What is a disadvantage of biological control?

When the biological control agent becomes a pest itself like the cane toad.

What is an advantage of biological control?

Reduces the use of chemical pesticides.