AQA-GCSE-Biology-B18-Biodiversity -and-Ecosystem -questions-and-kerboodle-answers

a Use the information in Figure 1 to calculate the percentage biomass passed on;

i from producers to primary consumers [2 marks]

5 000/50 000 × 100 = 0.1,

10% biomass passed on

ii from primary to secondary consumers [2 marks]

400/5000 × 100 = 0.08,

8% biomass passed on

iii from secondary consumers to top carnivores.[2 marks]

50/400 × 100 = 0.125,

12.5% biomass passed on

b In any food chain or food web, the biomass of the producers is much larger than that of any other levels of the pyramid. Why is this? [3 marks]

biomass of producers has to support whole pyramid, producers plant materials high in indigestible cellulose, relatively little biomass transferred from producers to primary consumers

c In any food chain or food web, there are only small numbers of apex carnivores. Use your calculations to help you explain why, [2 marks]

biomass lost at each stage of food chain/web,

limited biomass at top of food chain so few apex carnivores can be supported

d All of the animals in Figure 1 are cold-blooded.
What difference would it have made to the average percentage of biomass passed on between the levels if mammals and birds had been involved?
Explain the difference. [4 marks]

Mammals and birds regulate body temperature using energy from respiration of biomass,

meaning less biomass available for conversion to new biomass.

Cold-blooded animals use environment (not respiration) to regulate body temperature, which is more energy-efficient.

If mammals and birds had been involved instead of cold-blooded animals, average percentage of biomass passed between levels would be lower.

2 a Draw a flow chart showing acid rain formation.[5 marks]

b Figure 2 shows the sulfur emissions made by European countries from 1980 to 2002. Use this graph to help you answer the following questions:

i What was the level of sulfur emissions in 1980? [1 mark]

18 Tg

ii What was the approximate level of sulfur in the air in the year that you were born? [1 mark]

as appropriate

iii What was the level of sulfur emissions in 2002? [1 mark]

4 Tg

c What does this data tell you about trends in the levels of sulfur emissions sincel 980? [2 marks]

emissions have fallen steadily

and levelled out at a greatly reduced level

d Sketch the bar chart and show how you would expect it to have continued to the present day. Discuss your predictions. [6 marks]

Award marks for well-drawn bar chart correctly labelled, showing plateau or continued slow fall in emissions.

Points may include: effectiveness of emission control measures proven, control measures more widely implemented, control measures tightened, technologies improve.

3 The world population is increasing and there is food insecurity in many parts of the world.

a Explain the term ‘food security’. [3 marks]

having enough food to feed population

with food accessible to all

and with population aware of need for healthy, balanced diet

b Using pyramids of biomass, explain why there would be more efficient use of resources if people everywhere consumed less meat and more plant material and suggest how this might help solve some of the problems of food security. [6 marks]

Earth has limited surface area for plant growth; biomass lost at each stage of food chain, so shorter food chains more efficient; if people ate more plants instead of feeding plants to animals and then eating animals, food chains would be shorter; food production efficiency would be greatly increased as plant biomass would be used to produce human biomass directly. Award marks for well-drawn pyramids of biomass for plant/person and plant/animal/person.

c Give another problem with food security and suggest a way of solving the problem. [4 marks]
increasing birth rate (population increase) – educate people in use of contraception to control family size;

new pests and pathogens (attacking crops/animals and reducing yields) – develop pesticides, insecticides, medicines, and vaccines to protect food supply;

environmental changes (preventing production of crops/animals in certain areas) – reduce global output of greenhouse gases to stem climate change;

changing diets (scarce food supplies exported to developed countries) – education and regulation;

conflict (disrupting agriculture and destroying infrastructure) – negotiate peace;

cost of agricultural inputs (high price precludes use in developing countries, limiting yields) – education in use of compost and natural fertilisers, development of affordable inputs.

4 Chickens are often farmed intensively. The birds arrive in the broiler house as 1 -day-old chicks and are slaughtered at 42 days old when they weigh about 2 kg.

The temperature, amount of food, water, and fight levels are carefully controlled. About 20000 chickens are reared together in one house. The following table shows their weight gain each week.

a Plot a graph to show the growth rate of one of these chickens. [5 marks]

b Explain why the temperature is carefully controlled in the broiler house. [2 marks]

to limit use of biomass from food in respiration to regulate body temperature,

maximising biomass for growth

c Explain why so many birds are reared together in a relatively small area. [4 marks]

To reduce use of biomass from food in respiration for movement

as active, contracting muscles require high levels of energy from respiration

and energy is lost to the surroundings as muscles warm up.

This maximises biomass for growth.

d Why are these birds reared like this? [3 marks]

to meet increasing demand for cheap meat

by maximising conversion of biomass to meat

in the shortest possible time

e Draw a second line to show how you would expect a chicken reared outside in a free-range system to gain in mass, and explain the difference. [5 marks]

Award marks for line drawn beneath first line, clearly labelled.

Points may include:

free-range chickens use biomass in respiration to provide energy for movement and regulating body temperature, so convert less biomass from food for growth.