It is important to conserve fish stocks.

The image below shows a traditional fishing net and a new type of fishing net called SafetyNet.

SafetyNet has holes formed by LED light rigid rings.

 Describe how SafetyNet helps to conserve fish stocks.

State one other way of reducing overfishing.

Why should fish stocks be kept above a certain minimum level?

Fish can be grown in fish farms.

Fish farms are large cages in the sea.

Suggest why fish grown in cages grow faster than fish of the same species free in the sea.

Suggest two reasons why more of our fish are supplied by fish farming rather than from traditional fishing.

Saccharomyces cerevisiae is a type of yeast used in bread-making.

When the yeast cells respire, a gas is produced which makes the bread dough rise.

Complete the sentences below about brewing and bread making.

In brewing and bread making, respiration takes place.

Yeast use as a source of food.

The products of this type of respiration are a gas, , which makes the bread rise, and , which evaporates into the atmosphere during the baking process.

When the bread dough rises, its volume increases.

A group of students investigated the effect of temperature on the volume of bread dough.

The students:

1. Labelled 8 syringes with numbers from 1-8.
2. Made the bread dough using an active yeast suspension and a mixture of 50 g flour and 2 g sugar.
3. Poured 10 cm³ of bread dough inside each syringe.
4. Placed the syringes at different temperatures.
5. Recorded the volume of bread dough after 30 minutes.
6. Repeated the experiment 3 times.

The students' results are shown in the table below.

Calculate the average increase in volume at 30 °C.

Use the data in the table to plot a graph of the average increase in volume of bread dough against temperature.

Describe and explain the results shown by the graph.

Penicillin is produced commercially in fermenters.

Penicillin is a substance that kills bacteria.

What is the name given to substances that kill bacteria?

Name the type of microorganism that produces penicillin.

Fermenters need to be sterilised before being used to grow penicillin.

State how a fermenter can be sterilised.

The graph shows changes in glucose concentration, oxygen concentration and penicillin concentration inside the fermenter during the production of penicillin.

State the day in which the production of penicillin was fastest.

Describe how the concentration of glucose in the fermenter changes in the first day.

State what happens to the liquid containing penicillin after it is collected from the fermenter.

Farming techniques have evolved in the last decades.

Give three reasons why more land is being used for farming.

Describe how increased farming has decreased biodiversity and increased atmospheric pollution.

Scientists are increasingly concerned about food security.

Which of the following statements correctly describes food security?

Which of these would improve food security?

Explain how a large increase in the mass of meat eaten will decrease food security in the future.

Some areas in developing countries are used to grow crops that cannot be eaten by people.

The crops are used to produce biofuel.

Describe the advantages and disadvantages of growing these crops to produce biofuel.