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

B18.1 The Human Population Explosion AQA GCSE Biology B18 The Human Population Explosion: Page No. 287

1a Give three reasons why the human population has increased so rapidly over the past couple of hundred years. [3 marks]

Because, we have discovered how to grow more food than we could ever gather from the wild.

We can cure or prevent many killer diseases.

We have no natural predators. This helps to explain why the human population has grown so fast.

 

b Describe how people reduce the amount of land available for other animals and plants. [4 marks]

More and more land is used for building houses, shops, industrial sites, and roads on. This destroys the habitats of other living organisms and reduces biodiversity.

• We use billions of acres of land around the world for farming. Wherever people farm, the natural animal and plant populations are destroyed.

• We dig up vast areas of land for quarries to obtain rocks and metal ores, reducing the land available for other organisms.

• The waste produced by humans pollutes the environment and processing it takes up land, affecting biodiversity.

2 a Give three examples of resources that humans are using up.[3 marks]

Any three from:

1 Land.

2 Metal ores.

3 Fossil fuels, wood.

b List five examples of how the standard of living has improved over the past 100 years. [5 marks]

Any five examples are:

  • Use of electricity for lighting/heating/entertainment.
  • Increased food production.
  • Improved medicines.
  • Use of fossil fuels for transport.
  • Development of plastics • improved waste disposal • improved sanitation.

3 Explain in detail the different ways that the ever-increasing human population is causing pollution, [6 marks]

Points may include:

  • Increased waste – including bodily waste, industrial waste, packaging, uneaten food, and disposable goods.
  • Exhaust gases from transport.
  • Use of pesticides and fertilisers in farming.

B18.2 Land and water pollution AQA GCSE Biology B18 Land and water pollution: Page No. 289

1 a What is sewage? [1 mark]

Human bodily waste and waste water.

b Explain why is it important to dispose of sewage carefully. [5 marks]

Because toxic chemicals can spread from waste into soil, toxic chemicals can be washed into waterways,  sewage can pollute soil with dangerous chemicals and gut parasites,  toxins build up in organisms along food chain (bioaccumulation),  largest predators die or are infertile due to toxic chemical build‑up.

c What are bioindicators used for? [1 mark]

To monitor pollution level in waterways.

2 a Farming can cause pollution of the land. Describe the polluting effects farming can have on

i land

Polluting effects are:

  • Pesticides and herbicides spread from crops into soil.
  • Plant material contaminated with toxins.
  • Small levels of toxins taken in by animals eating affected plant material.
  • Toxins build up along food chains (bioaccumulation) until toxic levels are reached in top predators.

ii water. [6 marks]

Polluting effects are:

  • Fertilisers washed from the soil into streams, ponds, and rivers.
  • Nitrates in fertilisers encourage the rapid growth of algae and water plants.
  • Microorganisms feeding on the plants use up oxygen decreasing the levels of oxygen.
  • Other oxygen-dependent organisms then die because of a lack of oxygen.

b In the UK, a chemical called DDT was used up until the 1980s to kill insects. Large birds of prey and herons began to die and their bodies were found to have very high levels of DDT in them. Discuss how this might have happened and suggest why it took a long time for any link to be made. [6 marks]

Because: 

  • DDT in pesticide contaminated soil and waterways.
  • Organisms contaminated with toxins.
  • DDT builds up in organisms along food chain.
  • DDT levels become dangerously high in top predators (birds of prey, herons).
  • Effects of DDT not noticeable until dangerous levels reached.

• Route through food chain not obvious

B18.3 Air pollution AQA GCSE Biology B18 Air pollution: Page No. 291

1 Explain how acidic gases from cars and factories burning fossil fuels can pollute:

a air [2 marks]

 Acidic gases released into atmosphere and spread around by wind in this way pollute air.

b water [2 marks]

Sulfur dioxide and nitrogen oxides dissolve into rain and snow, contaminating lakes/rivers/streams.

c land. [2 marks]

Dilute sulfuric acid and nitric acid fall as acid rain and soak into soil.

2 a Complete a flow chart to show how acid rain is produced. [5marks]

Flow chart should include:

 Cars/power stations burn fossil fuels → acidic gases (e.g., sulfur dioxide, nitrogen oxides) formed → gases carried in the winds in atmosphere → sulfur acidic gases dissolve in rainwater and react with oxygen to form dilute sulfuric acid and nitric acid → acid rain falls.

b Explain why some countries that have strict controls on sulfur emissions still suffer acid rain damage to their buildings and ecosystems. [3 marks]

Sulfur dioxide and nitrogen oxides can be carried high in air by winds.  Acidic gases can be blown from a country that does not control its sulfur emissions to a country  that has strict emission controls and fall as acid rain.

3 a Look at Figure 2a. What was the percentage reduction in sulfur dioxide emissions in the EU between 1990 and 2010? [3 marks]

25000 − 5000 = 20000,  

× 100 = 80, reduction of 80%.

b Suggest two reasons for the observed reductions. [2 marks]

Any two reasons are:

  • More efficient catalytic converters in cars.
  • Cleaner fuels.
  • Legislation to control emissions from factories.

c Explain how you would expect these observations to affect the levels of acid rain in Europe. [3 marks]

Levels of acid rain should fall as sulfur dioxide emissions fall, unless prevailing winds carry acidic gases from non-European countries.

4 a Using Figure 2b, calculate the change in sulfur dioxide emissions for:

 i China, between 1850and 1975 [2 marks]

1850: 0 million tones.

1975: 4 million tones.

 4 million tone increase.

ii the USA, between 1975 and 2000. [2 marks]

1975: 14 million tones.

2000: 8 million tones.

 6 million tone decrease.

b Discuss the implications for global biodiversity of the trends seen in Figure 2b. [6 marks]

Figure 2b shows increasing global sulfur dioxide emissions, causing increasing acid rain.  Acid rain directly damages plant life by falling on plants and by soaking into soil and being taken up by roots.  Acid rain contaminates soil and watercourses, making them more acidic and eventually unable to sustain life.  Increasing sulfur dioxide levels threaten to reduce global biodiversity as whole ecosystems can be destroyed.

 

B18.4 Deforestation and peat destruction AQA GCSE Biology B18 Deforestation and peat destruction: Page No. 293

1 a Define deforestation. [2 marks]

Removal of large areas of forest by felling/burning without trees being replaced. 

b Explain how deforestation affects biodiversity – and why it matters. [4 marks]

Tropical rainforests contain more biodiversity than any other land environment.  Loss of forests means biodiversity of plant and animal life is also lost  as habitats are destroyed and species become extinct.  Many species are being destroyed before being identified and studied, so potential new sources of medicine or food could be lost.

2 Give three reasons why deforestation increases the amount of carbon dioxide in the atmosphere. [3 marks]

Carbon dioxide produced by burning of trees. 

Carbon dioxide produced by decomposition of dead vegetation.

 Less carbon dioxide removed from atmosphere by growing plants.

3 a Explain why the numbers of peat bogs and peatlands in the world are decreasing. [2 marks]

Use of peat as fuel and by gardeners as compost.

b Discuss why this is cause for concern. [4 marks]

CO2 is released into atmosphere as peat is burnt or used as compost,  increasing atmospheric levels of carbon dioxide  and depleting the carbon store. 

Destruction of peat bogs destroys habitats and reduces biodiversity.

4 Discuss the conflict between the need for cheap available compost and the need to conserve peat bogs and peatlands. [6 marks]

Points may include: 

  • Cheap compost needed by gardeners and horticulturists to improve soil properties, promote seed germination, and increase food production, alternative, ‘peat‑free’ composts are available but are less popular.
  • Peat bogs and peat lands vital to biodiversity as they form habitat for many organisms adapted to live in acidic conditions.
  • Peat forms very slowly and under very specific conditions – cannot be replaced as quickly as it is being used.

 

B18.5 Global warming AQA GCSE Biology B18 Global warming: Page No. 295

1 a Use the data in Figure 1 to produce a bar chart showing the maximum recorded level of carbon dioxide In the atmosphere every tenth year from 1 960 to 2010. [3 marks]

Correct y-axis label and scale, Correct x-axis label and scale, data plotted correctly.

b Explain the trend you can see on your chart. [3 marks]

Carbon dioxide levels rising steadily over time,  partly as a result of human activities.

c Describe the greenhouse effect. [5 marks]

Energy transferred from Sun to Earth. 

Much of this heat is reflected back into space, 

but  some is absorbed by greenhouse gases in the atmosphere and reradiated back to Earth.

Earth’s surface and atmosphere are warmed (greenhouse effect), maintaining conditions ideal for life

2 a Explain why global warming is occuring. [4 marks]

Atmospheric levels of greenhouse gases increasing  as a result of human activity, increasing greenhouse effect and causing global temperatures to rise.

b Describe two of the the biological consequences of global warming. [4 marks]

Any two from: 

  • Loss of habitat – reducing biodiversity.
  • Changes in distribution – some organisms may disappear from some areas as habitat changes.
  • Changes in migration patterns – caused by changes in climates and seasons.
  • Reduced biodiversity – some organisms will become extinct as climate changes.

3 Give an example of an organism that has been, or might be, affected by global warming. Explain the effect of global warming on the survival of this organism, [6 marks]

The effects of global warming are the environmental and social changes caused (directly or indirectly) by human emissions of greenhouse gases. There is a scientific consensus that climate change is occurring, and that human activities are the primary driver. Many impacts of climate change have already been observed, including glacier retreat, changes in the timing of seasonal events (e.g., earlier flowering of plants), and changes in agricultural productivity. Anthropogenic forcing has likely contributed to some of the observed changes, including sea level rise, changes in climate extremesdeclines in Arctic sea ice extent and glacier retreat.

B18.6 The impact of change AQA GCSE Biology B18 The impact of change: Page No. 297

1 a Define the following environmental changes:

i seasonal [4 marks]

Natural changes  in environmental factors such as temperature, rainfall level, water availability, dissolved gases in water, and daylight hours  between different seasons  in temperate parts of the world.

ij geographical [3 marks]

Natural changes  in environmental factors such as soil structure or pH, altitude, water salinity, and water availability  between different geographical areas of the world.

b State how organisms adapt to environmental changes. [3 marks]

Natural mutations cause features that enable some individuals within a population to cope better with a change to their environment.  These individuals are more likely to survive and breed (natural selection), passing on the beneficial feature to offspring.

2 a Look at Figure 3 and explain the overall trend in the data. [1 mark]

Number of breeding pairs of Dartford warblers in UK increasing.

b Suggest reasons for the changes in the numbers of breeding pairsofDartfordwarblersin 1963 and in 2010. [3marks]

 Dartford warblers cannot survive very cold winters. Number of breeding pairs dropped sharply in 1963,  suggesting cold winter that reduced population.  Number increased sharply in 2010, perhaps as a result of temperature increase.

 

c State which aspect of climate change seems to be most closely linked to a change in the distribution of British birds. Explain why.[6 marks]

As temperature changes. 

Changes in number of Dartford warblers indicate that numbers have increased as UK temperatures have increased but drop sharply after cold winters.  Drop in number of Dartford warblers in Spain indicates that too high a temperature also affects distribution.  Evidence suggests that change in mean UK temperature  and seasonal extremes of temperature  affect distribution of UK birds both within the country and between countries.

 

 

 

B18.8 Trophic levels and biomass AQA GCSE Biology B18 Trophic levels and biomass: Page No. 301

1 a Explain why it is important to maintain biodiversity. [3 marks]

Important for environmental health, offers potential source of new food crops,  offers potential source of new medicines.  

b Summarize the main ways people can help to maintain biodiversity. [5 marks]

Breeding programs for endangered species – restoring endangered species to sustainable populations,  protection and regeneration of rare habitats – protecting different animals and plants, reintroduction of field margins and hedgerows – allowing biodiversity to be maintained in agricultural land,  reduction of deforestation – maintaining habitats,  recycling resources – reducing habitat loss and pollution.

c Suggest an example of where there might be a conflict between maintaining biodiversity and human needs. [4 marks]

Any one from: 

  • Increased field margins limiting land available for food production,
  • Reduction of deforestation limiting land available for food production,
  • Taxes on landfill waste increasing costs to businesses.

2 Using the data in Figure 3a

a Describe the trend in carbon dioxide emissions in the UK since 1990. [1 mark]

Levels have fallen steadily.

b Suggest how this data demonstrates the effect of governments on carbon emissions. [3 marks]

Data suggests that Kyoto agreement drove UK government to take action to limit carbon dioxide emissions and that government intervention via legislation  has been successfully.

c Discuss three examples of how a fatl in carbon dioxide emissions globally might help maintain biodiversity. [6 marks]

Points may include:

  • Reduce or prevent increase in greenhouse effect and global warming – maintaining biodiversity by preserving Arctic and Antarctic ice habitat.
  • Preventing rises in sea levels that will destroy biodiverse mangrove forests.
  • Preventing temperature increase that could dry out wetlands and cause bleaching/death of coral reefs.

3 Using the data in Figure 4, suggest how taxes can be used to help reduce human damage to ecosystems and biodiversity. [4 marks]

Data shows that as landfill tax increased, amount of material going into landfill fell.

Taxes on waste and emissions  can be used as an effective incentive to change human habits  and promote research into less damaging alternatives (e.g., recycling rather than landfill). 

 

B18.9 Biomass transferAQA GCSE Biology B18 Biomass transfer: Page No. 303

1 a Why is biomass lost in faeces? [4 marks]

Some of the biomass ingested by an animal cannot be used. Most herbivores cannot digest cellulose in plant material. Most carnivores cannot break down and digest hooves, claws, bones, and teeth.  Indigestible materials are egested as faeces, meaning biomass is lost.

b Why do animals that are very active use up more of the biomass they eat than animals that don’t move much? [5 marks]

Biomass used in cellular respiration to provide energy for movement  and to supply energy and raw materials needed for building new biomass.  Active animals carry out lots of respiration as active, contracting muscles respire more. More of the biomass eaten is broken down and used for movement in active animals  and more energy is transferred to surroundings as muscles warm up.

2 a Draw a flow chart of a food chain [4 marks]

 Flow chart should include:  producers → primary consumer → secondary consumer → tertiary consumer → decomposers.

b Explain the ways that biomass is lost at each trophic level in your flow chart. [6 marks]

Biomass lost by consumers in faeces  – cellulose cannot be digested by herbivores, animal parts such as hooves/claws/bones/teeth cannot be digested by carnivores.  Biomass lost by producers and consumers in waste  – excess protein and water lost in urine, carbon dioxide and water lost in respiration. Biomass lost in consumers in maintaining a constant body temperature  – energy transferred to surroundings.

3 Explain why so much of the light from the Sun that lands on the surface of the Earth is not used in making biomass in animals.[5 marks]

Only about 1% of energy from Sun’s light falling on Earth (incident energy) used by plants for photosynthesis  to create biomass.  Plant biomass eaten by animals cannot all be digested.  Some is broken down and used in respiration to provide energy for living processes such as movement and regulating body temperature.  Only small amount of biomass eaten by animals used for growth to produce new biomass.

B18.10 Factors affecting food security AQA GCSE Biology B18 Factors affecting food security: Page No. 305

1 State what is meant by the term ‘food security’. [1 mark]

Having enough food to feed a population.

2 Describe three ways in which food security might be reduced and three ways in which food security might be increased. [6 marks]

Any three reducing factors from:

  • increasing birth rate,
  • new pests and pathogens,
  • changing diets in developed countries,
  • environmental changes,
  • cost of agricultural inputs,
  • conflicts.

 Any three increasing factors from:

  • maintaining or improving soil quality,
  • efficient ways to produce food (e.g., selective breeding or GM technology),
  • managing fish stocks,
  • educating populations.

    3 Look at Figure 1 and use it to help you explain how changing diets in one country can affect food security in another. [6 marks]

Quinoa staple food in Bolivia.  Production of quinoa in Bolivia has increased since 1997.  Quinoa has increased in popularity in other countries, leading to increased exports  as farmers can charge more to foreign buyers than to local consumers and make more money. Local consumption of quinoa has fallen as exports have increased.  Food security in Bolivia reduced as population increasingly dependent on imported pasta

4 ‘Food security is one of the biggest problems facing the human population today.’State whether you agree with this statement, and explain your answer using examples. [6 marks] 

Yes we are agree with this statement.

Afghanistan

Afghanistan about 35% of household is food insecure. Prevalence of under-weight, stunting, and wasting in children under 5 years of age is also very high.

Mexico

Food insecurity has distressed Mexico throughout its history and continues to do so in the present. Food availability is not the issue; rather, severe deficiencies in the accessibility of food contributes to the insecurity. Between 2003 and 2005, the total Mexican food supply was well above the sufficient to meet the requirements of the Mexican population, averaging 3,270 kilocalories per daily capita, higher than the minimum requirements of 1,850 kilocalories per daily capita. However, at least 10 percent of the population in every Mexican state suffers from inadequate food access. In nine states, 25–35 percent live in food-insecure households. More than 10 percent of the populations of seven Mexica states fall into the category of Serious Food Insecurity.

The issue of food inaccessibility is magnified by chronic child malnutrition as well as obesity in children, adolescents, and family.

Mexico is vulnerable to drought which can further cripple agriculture

B18.11 Making food production efficient AQA GCSE Biology B18 Making food production efficient: Page No. 307

1 a Explain why it is important to keep animals cool in hot temperatures. [2 marks]

So that animals do not have to use much biomass in cooling down,  leaving more biomass for growth.

b Why don’t animals turn all of the food they eat into new biomass? [4 marks]

Biomass lost through faeces, urea, and respiration for movement  and regulation of body temperature.

2 Explain why there would be more food for everyone if people only ate plants. [6 marks]

Earth has limited surface area for plant growth.  Biomass lost at each stage of food chain.Shorter food chains more efficient. If people all ate plants instead of feeding plants to animals and then eating animals, food chains would be shorter.  Efficiency of food production would be greatly increased as plant biomass would be used to produce human biomass directly.

3 Discuss the advantages and disadvantages of intensive methods for rearing farm animals and fish. [6 marks]

Advantages:

  • indoor work,
  • animals grow faster so ready for market sooner,
  • control of movement and temperature maximizes conversion of food to biomass, • weather conditions don’t matter,
  • fish farming conserves wild stocks.

Disadvantages:

  • initial cost of buildings,
  • cost of light and heating,
  • higher feed bills,
  • animals may be stressed (gain biomass more slowly),
  • ethical concerns.

 

B18.12 Sustainable food production AQA GCSE Biology B18 Sustainable food production: Page No. 309

1 a Explain how the fishing industry has reached crisis point.[2marks]

Development of large commercial fleets capable of catching huge quantities, uncontrolled overfishing.

b Describe three ways in which fish stocks can be protected.[3marks]

 Control size of the holes in nets so only largest fish caught, ban fishing during breeding season, strict catch quotas.

c Suggest possible reasons why these measures were not put in place a long time ago.[3marks]
Possible reasons may include: 

people dependent on fishing for livelihood and wary of reduced income, difficult to obtain overall picture of global fish stocks, difficult to apply quotas across large oceans fished by multiple countries.
2; Use Figure 1 to answer the following;

a When was the peak in cod catches and how many fish were caught?[2marks]

1969 (accept between 1967 and 1969)  1.8 million tonnes (accept 1.7 to 1.9 million tonnes).

b How many cod were caught in 2010?[1marks]

0.1 million tones.

c Calculate the percentage fall in catches from the maximum to the minimum on this graph. [3 marks]

1800000 − 100000 = 1700000,

 Percentage fall in catches = 1700000/1800000 × 100 = 94%.  

d Using the data in Figure 2, calculate the percentage increase in the Tuna catch from 1960-2000 in:

iAtlantic tuna.

0.4/0.1 × 100 = 400% increase.

ii Indian tuna.

1.2/0.25 × 100 = 480% increase.

iii Pacific tuna.

 3.6/0.6 × 100 = 600% increase.

e Suggest why the global fish crisis may have been left too late, [3 Marks]

Some fish species almost extinct, fish caught over quota discarded dead so cannot increase populations,  quotas difficult to enforce internationally.

3 Mycoprotein is an example of sustainable food production.
Discuss how it is similar to, and how its production differs from.intensive farming. [6 marks]

Similarities: 

  • fermenter equivalent to enclosed shed or barn.
  • fermenter temperature regulated and food supply maintained to give the optimum conditions.
  • designed to achieve maximum growth over minimum time.
  • cost of maintaining conditions outweighed by increased production. Differences:
  • fungus not an animal so controlled conditions cause no stress.
  • no ethical issues.
  • pH not monitored and maintained in farming.
  • no free-range alternative in mycoprotein production.

 

 

Summary questions: Page No. 310

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.

 

Practice questions: Page No. 311

01 Match each pollutant to its possible effect

 [3 marks]

methane – global warming

sewage – Increased risk of diseases

smoke – blackening of buildings

02 There are areas in deep seas where there are hot water springs called hydrothermal vents.

Volcanic activity creates an environment of very hot, acidic water.

No light reaches the deep seabed.

The environment is very extreme but many different organisms can live there.

02.1 Complete the following sentence.

Organisms that can survive in extreme conditions are called……………. [1 mark]

extremophiles

02.2 In the hydrothermal vents bacteria absorb toxic chemicals from the hot water. The bacteria use the chemicals to produce carbohydrates for the rest of the food chain.

The bacteria are eaten by limpets, which are eaten by crabs.

Draw and label a pyramid of biomass for this community. [2 marks]

correct order of organisms from base to top of pyramid: bacteria, limpets, crabs

box sizes decrease from base to top of pyramid

02.3 The food chains show some organisms that live near a hydrothermal vent and some organisms that live near the surface of the sea.

A food chain found near a hydrothermal vent: bacteria -> limpet -> crab

A food chain found near the surface of the sea: green seaweed -> iimpet -> crab

• Give a difference between the food chain found near a hydrothermal vent and the food chain found nearthe surface of the sea.

• Use information given in this question and your own knowledge to suggest reasons for the difference. [6 marks]

difference

  • food chain near hydrothermal vent begins with bacteria
  • food chain near surface of the sea begins with seaweed
  • use different energy sources
  • producers (in the two chains) are different

examples of scientific points made in the response

  • seaweed is an alga
  • seaweed absorbs light / energy from sun
  • for photosynthesis
  • to make glucose / sugar/ carbohydrate / food
  • no light at bottom of sea
  • plants can’t survive in the dark / conditions at the bottom of sea
  • bacteria are extremophiles
  • bacteria need different energy source / use chemical energy
  • to make carbohydrate / food

03 The fungus Fusarium is used to produce a proteinrich food that is suitable for vegetarians.

03.1 The What is the name of protein-rich food produced from a fungus? [1 mark]

mycoprotein

03.2 Figure 2 shows a fermenter that is used to grow large quantities of Fusarium.

The nutrient solution is sterilised before the Fusarium is added.

Suggest how the nutrient solution is sterilised. [1 mark]

steam kills organisms in the solution

03.3 What is the main food source for the fungus in the fermenter? [1 mark]

glucose (syrup)

03.4 Explain why air is bubbled through the nutrient solution, [2 marks]

provides oxygen / aerobic conditions

for respiration

03.5 Suggest one reason why it is important to constantly stir the contents of the fermenter. [1 mark]

any one from:

  • to prevent the fungus / Fusarium from settling at the bottom
  • to keep the fungus / Fusarium in contact with oxygen / nutrients

03.6 Explain in detail why the fermenter must have a cooling jacket around it. [3 marks]

respiration transfers thermal energy

if temperature rises (too much)

fungus / Fusarium would be killed