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B7 Ecology Mastery Booklet

Part 1: Communities, ecosystems interdependence

All organisms live in complex communities. These communities are made up of the populations of all the different species of animals, plants, protists, fungi, bacteria and archaea in a habitat (the natural environment of an organism). Within a community all species depend on each other. Within a community each species depends on other species for food, shelter, pollination and seed dispersal.Comprehension questions – each question should be attempted first from memory. Every five questions get your green pen and use the text to check your answers.

1. What is an organism?2. List the different types of organism that can form communities3. What is a habitat?4. List the 4 things species in a community rely on each other to provide

An ecosystem is created when the community of organisms is interacting with the non-living (abiotic) factors. In an ecosystem energy from the sun is transferred through the ecosystem in the chemical stores of chemical bonds. Material like carbon, nitrogen and water are recycled constantly.Communities of organisms often overlap both geographically and, in their need to compete for natural resources. This creates complex interdependence between species where the success or failure of one has effects on all the others on all the others.Comprehension questions – each question should be attempted first from memory. Every five questions get your green pen and use the text to check your answers.

5. What is an ecosystem?6. What is the source of the energy stored in the organisms’ chemical bonds?7. What happens to resources when two communities are overlapping

geographically?8. True or false. Interdependence means ‘each species can live independently and is

not affected by other species actions.Biotic and Abiotic factorsFor any organism to survive its needs to be well adapted to suit the environment in which they live. Abiotic factors are non-living factors like light intensity, temperature, moisture levels, soil pH, wind intensity and availability of oxygen and carbon dioxide. Each habitat will have a unique mix of abiotic factors causing different species to flourish. Biotic factors are the living components of an ecosystem. This include availability of food, new pathogens or parasites, new predators and competition between species.Comprehension questions – each question should be attempted first from memory. Every five questions get your green pen and use the text to check your answers.

9. Define ‘abiotic factor’10. What is a biotic factor?11. What is a community?12. What is a habitat?13. List 4 things species depend on each other for?14. What is an ecosystem?15. Where does all the energy in an ecosystem originate from?16. What materials are recycled through the ecosystem?17. What does interdependence mean?18. (from previous topic) what is a species?

Application questions – use your notes from this section and past sections to answer the questions below, but you should try from memory first.

19. Put the following keywords into the correct places in the Euler diagram Ecosystem, Community, abiotic factor, biotic factor. 1 Has been done for you

20. Complete the table Abiotic factors Biotic factorsFactor How does it affect

organismsFactor How does it affect

organismsLight intensity Availability of food

Temperature New pathogens and parasites

Moisture levels New predators

Soil pH Interspecific competition (competition between species)Wind intensity

Availability of oxygen and carbon dioxide

ECOSYSTEM

21. Complete the sentence belowSome people think an ecosystem is not the same as a community. They are wrong. In fact it is different because……

22. Zao is discussing our lesson “I think new diseases are an abiotic factor because you can get a cold from wet weather” Is she right? Give a reason for your answer

23. The Venus fly trap is a carnivorous plant. Explain why a Venus fly trap can grow in a low nitrogen soil.

24. How would the arrival of a new predator affect the population of a woodland area?

25. Frogs are very sensitive to changes in abiotic and biotic factors. What would a drop in frog population tell you about the water quality of the pond?

26. Red squirrels are native to the United Kingdom. Some years ago grey squirrels entered the country. They brought with them a new disease. The number of red squirrels is now very low. Is this an example of a biotic or abiotic factor?

Part 2: Distribution and abundance (required practical)

To study an ecosystem ecologists need to know the abundance (how many) and distribution (where they are found and in what number) of the organisms. This allows them to track changes over time and investigate various factors that affect a habitat. The challenge is it is impossible to measure the exact amount of an organism so ecologists use sampling techniques to get a realistic estimation of the true numbers. There are two main sampling techniques; Quadrats and Transects.Comprehension questions – each question should be attempted first from memory. Every five questions get your green pen and use the text to check your answers.

27. What does abundance mean?28. What does distribution mean?29. Why do we sample organisms and not count them all?30. What are the two sampling techniques?

QuadratsA quadrat is a simple square frame that is placed randomly on the ground to count the number of plant species. It is then moved to a different random location and the process is repeated. Only species completely within the frame are counted each time. It is important that as many quadrats as possible are taken during the sampling to ensure the result are valid (can be counted on to be true) It is also important that they are places randomly to avoid bias from the ecologist, aiming for a particularly good patch. To do this the area is broken up into a numbered grid. Then random co-ordinates are chosen. This could be achieved using a random number generator, or by rolling dice.Once a large number of results have been recorded a mean can be calculated. This provides quantitative data, allowing numbers to be compared between habitats and over time. The data can also be used to calculate the range, the median or the mode.TransectsTransects are not random sampling. They involve a line being placed along a varied habitat (eg a coastline from sea to beach) and regular recording of species using a quadrat. This allows you to see how the distribution of a species changes as the habitat changes and is a useful way of investigating how abiotic factors affect a species.Comprehension questions – each question should be attempted first from memory. Every five questions get your green pen and use the text to check your answers.

31. What is a quadrat?32. Should you count species partially in the quadrat?33. Give two ways of randomly positioning quadrats34. What is quantitative data?35. What are the 4 statistical processes ecologists do to their data?36. What is a transect designed to investigate?

Maths skillsMean: Is the average. It is the sum of the results divided by the number of resultsRange: The smallest to biggest valueMedian: Is the middle value if they were lined up in orderMode: Is the most common valueConsider the data below:3 4 3 4 5 2 6 7 3 3

37. What is the range?38. What is the mean?

39. What is the median?40. What is the mode?


41. Compare the similarities and differences between quadrat and transects

42. Explain the ways in which the information you get from a quadrat and transect are similar and different?

Key words to use: While, whereas, similarly, contrastingly, in much the same way

43. Some weed killers are selective.Selective weed killers kill broad-leaved weed plants, but do not kill narrow-leaved grass plants.The diagram below shows some weeds growing on a grassy lawn.

Some students investigated the effect of a selective weed killer on the weeds growing in a lawn. They used 0.5 m × 0.5 m quadrats.The lawn was 20 metres long and 10 metres wide.This is the method used.1. Divide the lawn into two halves, side A and side B.2. Place 5 quadrats in different positions on side A.3. Place 5 more quadrats in different positions on side B.4. Count the number of weed plants in each quadrat.5. Spray side A with weed killer solution.6. Spray side B with the same volume of water.7. Repeat steps 2-4 after 2 weeks.(a) Suggest a method the students should have used to place each quadrat.

(b) Give the reason for the method you suggested in part (a).

(c) Explain why the students used water on one side of the lawn instead of weed killer.

The table below shows the students’ results.

Number of weeds per quadratAt start After 2 weeks

Side A (Weed killer)

Side B (Water)

Side A (Weed killer)

Side B (Water)

8 14 3 82 9 4 15

12 3 0 715 16 2 1213 3 1 13

Mean 10 9 2 X(d) Calculate the mean value, X, in the table above.(e) Calculate the percentage decrease in the number of weeds on

side A after 2 weeks.Use the following equation:

(f) One student thought the results were not valid.

Suggest one improvement the students could have made to the method to make the results more valid.Give the reason for your answer.

44. Students investigated the distribution of a green alga on a tree trunk.

The students:• tied a piece of string horizontally round a tree• put a quadrat on the string so that the quadrat

faced south• estimated the percentage of the area in the

quadrat covered with the green alga

• repeated the observation with the quadrat facing south west, west, north west, north, north east, east and south east.

(a) The diagram shows the quadrat the students used.

Describe how you would estimate the percentage of the area covered with the green alga in one quadrat.

(b) The bar chart shows the students’ results.

Direction the quadrat faced(i) How does the direction that the quadrat faced affect the percentage area covered with the green alga?(ii) What was the mode of the percentage area covered with the green alga?Give the reason for your answer.(iii) Give three environmental factors that might affect the distribution of the green alga on the tree.(iv) Suggest how one of the factors you gave in part (b) (iii) might have caused the distribution of the green alga shown on the bar chart.(c) Nitrophyte lichens grow on the bark of trees. These lichens are indicators of air pollution by ammonia. Ammonia concentrations in the atmosphere are often high in agricultural areas.The graph shows the relationship between air quality and the distribution of nitrophyte lichens.

High atmospheric Low atmospheric ammonia ammonia

Air quality scores© U.S. Department of Agriculture

(i) Describe the relationship between atmospheric ammonia and the abundance of nitrophyte lichens.(ii) How useful would a particular value for the abundance of nitrophyte lichens be as an indicator of ammonia pollution of the atmosphere?Explain your answer.

Part 3: Competition

As each species forms part of a community in an ecosystem they often find themselves in competition for limited resources. Animals compete for food, water, territory (space) and mates. Plants compete for light, water, nutrients (minerals) and space. The organism that outcompetes its neighbours will increase its chances of survival and therefore reproducing. Organisms have evolved many complex ways of outcompeting other species, but it is also important to remember that within a species individuals will also compete. Comprehension questions – each question should be attempted first from memory. Every five questions get your green pen and use the text to check your answers.

45. List the things animals compete for46. List the things plants compete for47. What things do both animals and plants compete for?48. What are ‘resources’49. Why do organisms compete?50. (prior knowledge) What is evolution?51. (prior knowledge) How does evolution help a species compete?52. What is the reward for successful competition?53. Find the mean, median, mode and range of the following data set:

9,4,17,4,7,8,1454. (prior knowledge) What is an organism?55. (prior knowledge) What is the difference between an ecosystem and a habitat?


56. A Stag is a male Deer. During the spring they grow large antlers from their head. They use them to fight each other. The winner becomes the alpha male of the group and can mate with the female deer. Explain why the Stag who uses the most energy to grow antlers will have the greatest chance of reproducing.

57. Rhododendrons are a type of plant not native to the UK. They grow a very thick canopy of leaves which drop in the winter to cover the ground and take a long

time to decompose. Explain why it is rare to find any other species competing to grow in the same area.

Part 4 Adaptation

Evolution is a process that happens over a very long period of time. Natural selection is a part of evolution and is continually happening. For an organism to survive long enough to breed it must be well adapted to the abiotic factors of its habitat. Adaptations are changes to an organism to suit a location. No matter where you go on the planet you will find life that has adapted to survive there. This demonstrates the amazing ability for organisms to change over long time periods to suit even the most extreme environments.Comprehension questions – each question should be attempted first from memory. Every five questions get your green pen and use the text to check your answers.

58. (prior knowledge) what is natural selection?59. (prior knowledge) what are abiotic factors? Give 3 examples.60. (prior knowledge) why can you not see a species evolve in front of your eyes?61. (prior knowledge) What are biotic factors? Give 3 examples.62. What is an adaptation?

Extremophiles as organisms that live successfully in the most extreme environments. Many are micro-organisms like Archaea and Prokaryotes, but some are complex organisms like fish and worms. They have been found living in extreme heat, like the hydrothermal vents in the ocean that reach over 80oC. They have been found in the extreme cold of -15 oC. Some even survive the high salt concentration of the Dead Sea.Most adaptations allow an organism to survive in an area another cannot. This prevents them from having to compete for space and territory. Other adaptations in plants are focussed on outcompeting other species for light, water or the ability to spread their seeds further. In hot climates plants try to reduce their surface area, increase the spread of their roots, or store water in their stem to prevent water loss.Animal adaptations often involve attracting a mate. They also have many adaptations to allow them to eat certain food more efficiently. Herbivores have specially adapted teeth that are better at grinding up plant cells, whereas carnivores have sharper teeth to slice meat. Camouflage is often important for either predator and prey alike, as is the ability to maintain a constant internal body temperature in either hot or cold climates, which is often achieved via surface area to volume ratio. In general animals in colder climates have thick wide bodies and limbs to lower the surface area to volume ratio and reduce heat loss. Animals in hot climates will have thin limbs and long bodies to help lose heat by increasing their surface area to volume ratio.Comprehension questions – each question should be attempted first from memory. Every five questions get your green pen and use the text to check your answers.

63. What is an extremophile?64. What is the temperature range life can be found in?65. Why are some species adapted to live in harsher climates?66. (prior knowledge) What factors affect the rate of transpiration in plants?67. How do plants prevent water loss?68. Compare the teeth of a carnivore and a herbivore?69. What adaptation is important for most animals?70. What surface area to volume ratio is good for colder climates?71. Compare the adaptations of animals to hot and cold climates

Hot climates Cold climates


72. Some animals are adapted to survive in very cold conditions such as the Arctic.Explain how the adaptations of Arctic animals help them to survive in cold conditions.“ The arctic is a harsh climate because……animals have adapted to survive it by….this helps because…for example..”

73. The Arabian oryx (Oryx leucoryx) is a mammal that was once extinct in the wild.

The image shows an Arabian oryx.

Describe the adaptations of the Arabian oryx to living in hot desert environments.

Use information from the image.

74. Figure 1 shows two types of seaweed which live in similar seashore habitats.

Most of the time the two seaweeds are covered with water.Bladder wrack has bladders filled with air.

Name the seaweed that will grow the fastest and explain why.

75. Figure 2 shows an angler fish.

Angler fish live at depths of over 1000 m.

In clear water, sunlight does not usually reach more than 100 m deep.Many angler fish have a transparent ‘lure’ containing a high concentration of bioluminescent bacteria.Bioluminescent bacteria produce light.

Suggest an advantage to the angler fish of having a lure containing bioluminescent bacteria.

Part 5: Feeding relationships

All species in an ecosystem live in a finely tuned balance. This interdependence requires biomass to be added by plants, algae and phytoplankton through photosynthesis. Biomass is the scientific name for all the matter in living things. Using sunlight absorbed by chlorophyll in the chloroplasts they turn carbon dioxide and water into glucose. They also produce oxygen, which they and all other aerobically respiring organisms require to survive.For these reasons’ photosynthetic organisms like plants, algae and phytoplankton are called producers. Their biomass forms the foundation of all feeding relationships.

Comprehension questions – each question should be attempted first from memory. Every five questions get your green pen and use the text to check your answers.

76. (prior knowledge) What is an ecosystem?77. (prior knowledge) What is biomass?78. (prior knowledge) Write the word equation for photosynthesis79. What does ‘aerobic’ mean?80. Write the word equation for aerobic respiration.81. Why do all organisms need to respire?The herbivores that feed off the producers are known as primary consumers. They range massively in size from aphids to hippos on land. In the oceans they range from microscopic zooplankton to fish.The carnivores that eat the primary consumers are known as secondary consumers. The tertiary consumers subsequently eat the secondary consumers and so on.


82. What is a consumer?83. What is a herbivore?84. Give 3 examples of herbivores85. What is a carnivore?86. Give 3 examples of carnivoresSimple feeding relationships are shown in a food chain. These are often over simplistic as a consumer might eat more than one organism from the level below. Instead we represent these as food webs.

Predators are organisms which hunt and kill their food. They are specially adapted to successfully capture and kill their prey. The prey also has adaptations which try to prevent their deaths and escape capture. As such over time a complex predator-prey relationship builds up. If conditions favour the prey, such as plentiful food, the prey will reproduce and increase in number. This then creates a large supply of food for the predator, so it is more successful and breeds increasing its number. This increase in predators causes over hunting of the prey, reducing their numbers. This in turn reduces the food supply for the predators so their numbers dwindle. The cycle continues.


87. Define food web88. Define predator and give an example from the diagram89. Define prey and give an example from the diagram90. Using the food web above write 3 food chains.91. What will happen to the number of owls and mice if the birds eat more

grasshoppers92. Why will the number of prey increase if the number of predators drops?93. Why will the number of predators increase if more prey are born?94. Use the cycle below to illustrate the predator prey cycle. Start with plentiful food

for the prey.


95. Explain why the population of a prey is linked to the population of a predator.

96. Look at the graph below

Describe the changes in the population of the arctic hare. Explain the role of the Canadian lynx in those changes.

97. A food chain in the North Atlantic Ocean is:

diatoms → small fish → large fish

The graphs show how over a year:

the population size of diatoms in the North Atlantic varies;

the light intensity alters; the concentration of nitrate

and phosphate minerals alters.

(a) Explain why the light intensity is a major factor in controlling the numbers of diatoms.

(b)

(i) Suggest two reasons why the population of diatoms decreases between spring and summer.

(ii) Give two reasons why the population of diatoms decreases in autumn.

(c) Use the information on the graph to suggest what change causes the number of diatoms to increase in the late summer. Give a reason for the change.

Part 6- Material Cycling

The earth is a closed system, there is a fixed amount atoms. All the new things that grow have to come from somewhere, so life has evolved to constantly recycle important nutrients like carbon and nitrogen. One of the biggest problems is what happens to all the dead organisms. One of the main outcomes of life is death. All species are constantly producing dead tissues, from the skin humans shed every day, to the leaves that fall in the autumn from trees. Decomposers play a vital role in the recycling of nutrients. They are a group of organisms which have adapted to feed on waste and dead animals and plants. They use them as food and in the process release the nutrients back into the environment as useful compounds like carbon dioxide into the air and nitrates into the water. Plants can then absorb the nitrates through their roots and carbon dioxide through their leaves. Most decomposers are microorganisms like bacteria and fungi. Others, called detritus feeders (or detritivores) start the process of

decay off. Examples include maggots, worms and beetles. Microorganisms can even live off the waste and corpses of detritivores


98. Why did nutrient cycles evolve?99. Give two examples of dead tissue which comes from living organisms

100. What do decomposers feed on?101. What do decomposers do with excess nutrients?102. How do plants absorb nitrates?103. What are decomposers who are not microorganisms called? Give two

examples

Carbon cycle

104.

Water cycle

105. Write the following processes correctly on the diagram Precipitation – as water droplets in clouds get heavier they fall as rain, hail,

sleet & snow. Condensation – the moist air rises and the water vapour condenses and

cools, producing clouds. Evaporation – the Sun heats the Earth’s surface, water evaporates to form

water vapour. Percolation – water trickles through gaps in the soils and rocks Transpiration – water is lost from the leaves surface

106. List the processes that remove carbon dioxide from the atmosphere107. List the processes that add carbon dioxide to the atmosphere108. What is a decomposer?109. What is the difference between fungi and detritovores110. What aspect of the carbon cycle has been changed by human activity

111. Use the words in the box to fill in the gaps in the diagram. You may use each word once or not at all.

carbon burning decay eatennitrogen oxygen pollution respiration

(b) (i) Why are fungi called decomposers?

(ii) Give one other type of decomposer.


112. The diagram shows part of the carbon cycle.

Use the information in the diagram and your own knowledge to describe in detail how carbon is cycled between living organisms and the air.

Your answer should include the names of any processes involved.

113. The diagram shows the mass of carbon dioxide released into and removed from the air each year in billions of tonnes.

Describe the processes shown on the diagram that exchange carbon dioxide with the air.

Explain the overall effect of these processes on the mass of the carbon dioxide in the air.

114. Use words from the box to complete the sentences about the water cycle.

boils condenses evaporates freezes

melts rain sea Sun wind

Water _______________ from the surface of the ______________ . Heat from

the ________________ speeds up this process and so does the ____________.

Water vapour in the atmosphere cools down and ____________ to form billions

of tiny water droplets. Some of the droplets join together and fall as ____________ .

(b) The diagram shows some processes in the carbon cycle.

(i) What is the name of substance X?

(ii) Which process, A, B, C, D or E, takes the longest and approximately how long does it take?

Part 7- Rates of decomposition (TRIPLE)

The rate of decomposition, like any chemical process, is affected by the conditions it happens in. This is often exploited by humans with the storage of food in freezers, or other preservative techniques like pickling. Decomposition relies on decomposing organisms to digest the tissue. These organisms can digest the tissue faster under certain conditions:

Temperature: Decomposers use enzyme-controlled reactions. This means they are very sensitive to temperature changes. Too cold and the rate of reaction will be slow, too hot and the enzymes will denature killing the decomposers.

Moisture: Microorganisms grow much faster in moist conditions. Dead tissues are easier to digest when wet. This means decay happens much faster when there is enough water.

Oxygen: Nearly all decomposers respire aerobically. This means that they need a plentiful oxygen supply to allow them to respire efficiently. Decay happens faster if there is a plentiful supply of oxygen.


115. What does decomposition mean?116. List the three factors that effect the rate of decomposition117. Give two ways humans have invented to slow the decomposition process118. (prior knowledge) what is a microorganism? Give 3 examples119. (prior knowledge) True or false: all microorganisms are prokaryotes.120. What happens when enzymes get too hot?121. Why does wet tissue decay faster?122. Why is a temperature of 30-400C best for decomposition?123. What will happen to the rate of decomposition if there is not enough

oxygen?

The household compost bin is a common example of the value of decomposing in nutrient recycling. The compost bin is often a dark colour, which allows it to absorb infra-ed radiation from the sun, warming it up. It also has vents to allow oxygen in and a lid to prevent water loss.

Bacteria can decompose waste material anaerobically (in the absence of oxygen). When they do this, they produce biogas. Biogas is mainly methane and made in a biogas generator, a large pit designed to decompose animal and agricultural waste anaerobically. The gas produced is used to heat homes, cook or as a fuel for vehicles. This is a good strategy for agricultural communities in developing countries.

124. Why are compost bins dark in clour?125. (prior knowledge) define anaerobic respiration126. What decomposing organism can respire anaerobically?127. What are 3 benefits of biogas reactors?128. (prior knowledge) what environmental problem is caused by methane

being released into the atmosphere?


129. Why does compost rot down faster in the summer than the winter?

130. Look at the data below from a biogas generator

131. Compare the volumes of gas produced by each type of waste.

132. What does this data tell you about the amount of energy stored in each of these wastes?

133. What would happen to the volume of gas produced if the temperature doubled? Why?

134. The image below shows a model biogas generator.

Students used the model biogas generator to investigate which type of food waste produces the greatest yield of biogas.

Gas collects in the balloon. The gas is then released through the valve and is burned at the Bunsen burner.

The students:

• put 500 g of potato peelings in the plastic bottle with some water and sealed the apparatus

• released the gas from the balloon after day two and timed how long the gas burned for

• released the gas that had collected in the balloon from day two to day four and timed how long the gas burned for

• repeated the investigation using 500 g of cooked rice, then 500 g of cabbage leaves and then 500 g of cooked pasta.

(a) Table 1 shows the students’ results.

Table 1 (i) Suggest why the gas collected in the balloon and released after day two did not burn.

(ii) Suggest why potato peelings produced the most biogas.

(b) Scientists investigated the production of biogas from different types of animal manure.

Table 2 shows the scientists’ results.

Table 2

Type of mannure

Volume of biogas produced

Methane in the biogas

Type of food waste

Length of time the gas burned in seconds

After day two From day two to day four

Potato peelings 0 175

Cooked rice 0 100

Cabbage leaves 0 150

Cooked pasta 0 160

in m3

per kg of manureas % of total

volume

Cow 0.34 65

Pig 0.58 68

Hen 0.62 60

Horse 0.30 66

Sheep 0.61 67

(i) Calculate the volume of methane produced from 1 kg of cow manure.

(ii) One scientist concluded that it would be better to use sheep manure in a biogas generator than to use cow manure.

What is the evidence for this conclusion?

Use information from Table 2 in your answer.

135. Some students investigated the production of biogas from animal manure.

They used the apparatus shown in the diagram.

In their first investigation, the students collected the biogas in the gas syringe.

The table shows the percentage composition of the biogas.

To make the biogas a more efficient fuel, the percentages of two of the gases in the table should be reduced.

(a) Which two gases should these be?

(b) The students then used the apparatus for a second investigation.

They bubbled oxygen through some fresh manure and water for one hour.They then set up the apparatus again and collected a second sample of biogas in the gassyringe.

Predict the effect of this procedure on the composition of the second sample of biogas. Explain your answer.

136. The table shows the sources of some of the energy used in India between 1960 and 1970.

Gas Percentagecomposition

Methane 55

Carbon dioxide 40

Water vapour 5

Source of energy in millions of tonnes

Non-renewable fuels Renewable fuels

Year Coal Oil Cow dung Vegetable waste

1960 47 7 101 31

1965 64 10 112 34

1970 71 15 123 38

(a) The change in the use of renewable fuels differs from that of non-renewable fuels. Calculate the percentage of renewable fuels used in 1960 and in 1970. Show clearly how you work out your final answer.

(b) The Indian government suggested that villagers should make better use of renewable resources.

They introduced biogas generators. The diagram shows one type of biogas generator.

The table shows the economic costs and benefits of using this type of generator.

Feature Cost or profit in £s

Cost of generator and fitting

250

Annual maintenance costs

40

Annual profit from gas produced

30

Annual profit from fertiliser produced

40

Evaluate the advantages and disadvantages of using this type of generator.

(c) The table shows how temperature affects the rate of biogas production in the generator.

Temperature in °C 10 15 20 25 30 35 40

Volume of biogas producedeach day in m3 0.50 0.55 1.50 1.70 3.00 3.45 3.30

(i) Use the grid to draw a graph to show how temperature affects the rate of biogas production.

(ii) Temperatures in India may reach over 35 °C. Explain the advantage of the generator being mainly underground.

Part 8- Human population and biodiversity

Modern humans have existed on earth for less than one million years. This is less than 0.02% of the entire time life has been on earth. Yet in that tiny fraction of time our actions have made huge and permanent changes to the earth.Biodiversity is the measure of the variety of all species on earth, or in a particular ecosystem. In general, high biodiversity is good for the stability of ecosystems. It reduces the risk of collapse that would happen if an ecosystem was dependent on one species for food or shelter. The success of the earth to maintain viable for life is dependent on maintaining a high level of biodiversity.In 2019 there are 7.7 billion (7.7x109) people on the earth, with an increase of 82 million (8.2x107) people each year. This was not always the case 200 years ago the global population was under 1 billion people. The increase in the population is mainly due to the increase in medical technology and the availability of food. This had led to a large rise in

life span and a huge reduction in infant mortality (the rate at which new-born children die) Comprehension questions – each question should be attempted first from memory. Every five questions get your green pen and use the text to check your answers.

137. What is biodiversity?138. (prior knowledge) what is an ecosystem?139. Why has human population expanded so much? Give 2 reasons.

As the population has grown the demand humans place on the environment have increased. We have reduced biodiversity and destroyed ecosystems by using the land for:

1. Building of houses, roads and other infrastructure.2. Farming to provide us with the plants and animals we eat.3. Mining to remove the vast quantities of oil and metal ores needed to build the

modern worldPeat bogs are a good example of this. Humans remove the peat to use as a compost in their gardens. The peat bogs formed over thousands of years and once dug up it can take over 100 years to grow back. This destroys the habitat of peat-dwelling organisms, reducing biodiversity.Palm oil is another example. Jungles are cut down to plant palm trees to sell the oil, reducing the size of the jungles in countries like Burma, which are home to Orangutans. The palm oil is used in foods and to make biofuelsHumans don’t just affect the environment by what we remove. Humans also release a huge amount of waste as sewage, litter and as a by-product of industrial processes. These can have a massive effect on ecosystems and biodiversity.As the population rapidly increases it is becoming harder and harder to manage the amount of waste we produce. We risk damaging the water and air supply, affecting both the lives of the humans and the native species that reside in a particular habitat. Comprehension questions – each question should be attempted first from memory. Every five questions get your green pen and use the text to check your answers.

96. (prior knowledge) What is a habitat?97. Give three examples of ways humans reduce biodiversity98. List 5 ways the quality of life has improve in the last 200 years99. Give two examples of waste products that humans contribute to the environment

that reduce biodiversity100. (maths question) What will be the global population in 2020?101. (maths question) Calculate the percentage increase in population from

2019 to 2020


102. Use the graphic organiser below to illustrate the various ways humans can reduce biodiversity the first one has been done for you.

Use of pesticides

One type of crop grown

Woods cut down

Farming:

Reduced biodiversity

103. Write a paragraph to explain the different ways humans reduce biodiversity. Include both the things we remove and the things we add to the environment.

104. Improving the quality of life for everyone without damaging the planet for the future is known as sustainable development.One problem is the rapid growth in the Earth’s population of humans during the last 500 years. This is shown by the graph.

(a) When the Earth’s population was much smaller, the effects of human activities on forests were usually small and local.In the past 500 years there has been large-scale deforestation in some areas. Give tworeasons for this.

(b) Look at the bar chart. It shows the average amount of energy used by each person in one year in the USA, Japan and Bangladesh. (i) Suggest one reason why so much more energy is used per person in the USA than in Bangladesh.

(ii) Using a lot of resources for energy harms the Earth.Explain why.

(c) As we are using more resources, waste management is becoming more important. In the UK much of the solid waste is still being dumped in landfill sites. In 1996, the UK government introduced a landfill tax because landfill sites were being used up. However, the year after the landfill tax was introduced it was estimated that 18 million tonnes of landfill waste was not reported. The government was trying to encourage other forms of waste management, such as:

• reduce waste• reuse waste• recycle waste

(i) Explain the main problem caused by the landfill tax.

(ii) Describe one example of how each of the different forms of waste management can be put into practice.

• reduce waste• reuse waste• recycle waste

105. The figure below shows the amount of forest cover on an island in Asia, in 1973 and in 2010.

(a)(i)Deforestation has decreased the amount of forest cover on the island.

Describe the change in the pattern of forest cover on the island.

(ii)Give two possible reasons why the amount of forest has decreased between 1973 and 2010.

(b)Scientists are concerned about the effects of a decrease in forest cover on ecosystems. Give two possible negative effects of the decrease in forest cover on ecosystems.

106. Human activities have many effects on our ecosystem.

The graph shows the volume of peat compost and peat-free compost used in gardening from 1999 to 2009.

(a) Describe the trends shown in the graph.

(b) What effect does the destruction of peat bogs have on the gases in the atmosphere?

(c) Deforestation is also damaging ecosystems.

Describe one effect of deforestation on ecosystems.

Part 9- land and water pollution

Land pollution:Human activities often pollute the land. Most land pollution is either the result of deliberate pollution from toxic industrial by-products, human sewage or from farming.Use of fertilisers, pesticides (chemicals the kill insects) and herbicides (chemicals that kill weeds) can significantly pollute the land if used in high levels.

Water pollution:

Everything that humans do to the land in time will end up in the water. This is due to rainfall causing water run off the land into the rivers and streams. If fertilisers build up in a lake, they can cause the algae to grow incredibly quickly. They cover the surface of the pond blocking out the light to the plants at the bottom. These underwater plants die and are fed on by decomposers which use up all the oxygen in the water. The lack of oxygen kills the fish and other aquatic animal life. This process is called eutrophication.

Pesticides and Herbicides can cause a problem due to bioaccumulation. This is when the chemicals that are in low levels in the water begin to build up in producers and primary consumers. These levels are still too low to kill the organisms, but the consumers above them eat many and the toxins begin to build up as they flow up the food chain. By the time the top carnivore has fed the amount of chemical is in much higher concentration and kills them.

Some species are very sensitive to pollutants. These species can either die out quickly or thrive in poor water and air conditions. Scientists use these bioindicator species to quickly judge the quality of air and water.


170. What are fertilisers?171. What do herbicides do?172. What are pesticides?173. Give 2 ways humans can pollute the land174. Explain why land pollution often leads to water pollution175. Why could sewage lead to eutrophication in a similar way to fertilisers176. Why do farmers use herbicides and pesticides on their crops?


177. Freshwater streams may have different levels of pollution. The level of pollution affects which species of invertebrate will live in the water.

Table 1 shows the biomass of different invertebrate species found in two different streams, X and Y.

(a) The bar chart below shows the biomass of invertebrate species found in Stream X.

i. Complete the bar chart by drawing the bars for water louse, bloodworm and sludge worm in Stream Y.

Species present

Biomass in g

Invertebrate species Stream X Stream Y

Mayfly nymph 4 0

Caddis fly larva 30 0

Freshwater shrimp 70 5

Water louse 34 10

Bloodworm 10 45

Sludge worm 2 90

Total 150 150

ii. Table 2 shows which invertebrates can live in different levels of water pollution.

Table 2

Pollution level Invertebrate species likely to be present

Clean water Mayfly nymph

Low pollution Caddis fly larva, Freshwater shrimp

Medium pollution Water louse, Bloodworm

High pollution Sludge worm

Which stream, X or Y, is more polluted? Use the information from Table 1 and Table 2 to justify your answer.

(b) There is a sewage works near another stream, Z.

An accident caused sewage to overflow into Stream Z.Two weeks later scientists took samples of water and invertebrates from the stream.They took samples at different distances downstream from where the sewage overflowed.The scientists plotted the results shown in Graphs P and Q.

Graph P: change in water quality downstream of sewage overflow

Graph Q: change in invertebrates found downstream of sewage overflow

I. Describe the patterns shown in Graph P.II. Describe the relationship between dissolved oxygen and the survival of

mayfly nymphs in Stream Z. Suggest a reason for the pattern you have described.

(b) Many microorganisms are present in the sewage overflow. Explain why microorganisms cause the level of oxygen in the water to decrease.

178. Two groups of students, Group 1 and Group 2, were monitoring the oxygen concentration in a river.

They measured the oxygen concentration of the water at points W, X, Y and Z. The measurements were taken on the same day, but the two groups used different oxygen sensors.

The sensors for both groups were working properly.

The results for the two groups are shown in the table.

Concentration of oxygen in arbitrary units

Sampling position W X Y Z

Group 1 9.4 9.3 9.4 8.5

Group 2 9 9 9 9

(a) The results of Group 2 did not show any difference in the concentration of oxygen at the four different sampling positions. The results of Group 1 did show differences. Suggest why.

(b) The results of Group 1 show the lowest concentration of oxygen was at sampling position Z. Suggest why.

(c) The students also counted the number of different invertebrates living in the river at points W, X, Y and Z. The results are shown in the table.

InvertebrateSampling position

W X Y Z

Stonefly larva 4 5 4 0

Water snail 16 15 16 10

Bloodworm 0 0 0 25

Freshwater louse 6 5 7 5

From these results, which invertebrate is not suitable as an indicator of oxygen concentration in water? Give a reason for your choice.

177. Human activities affect the environment.

(a) Deforestation results in an increase in carbon dioxide levels in the atmosphere. Give two reasons why.

(b) In this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate.

A dairy farmer washes out his cow shed each day. The waste water contains urine and faeces. The waste water overflows into a stream by mistake.

The waste water will have an effect on the plants and invertebrates living in the stream.

Explain why.

Part 10- Air pollution

Most air pollution is the result of humans burning fossil fuels. The exhaust gases cause problems like acid rain, smoke, smog and global warming.Acid rain:Acid rain is caused by gases that come from vehicles and factories. Sufur dioxide and nitrous oxides dissolve into the water in clouds forming acidic compounds. When the rain falls its kills the trees, hurts water-based life and destroys marble and limestone buildings. Acid rain is being reduced by countries burning less coal and fitting catalytic converters on their vehicles. This is harder to do in less economically developed countries.Smoke pollution:The tiny particulates of soot travel in the air they reflect the sunlight causing a global temperature to drop, known as global dimming. It also has a short term effect in that it irritates human lungs leading to breathing problems.Smog:Smog is caused by all the chemicals above. It forms a cloudy haze that is seen over major cities and has been suggested that it contributes to lower life expectancy for people that live in cities compared to those that live in the countryside.Global warming:Carbon dioxide, methane and water vapour are gases which are all able to reflect infra-red radiation. When the light from the sun strikes the earth it warms it and bounces off. He greenhouse effect is when the gasses reflect the heat back to the surface warming it. This small change creates significant differences to the global climate.

Climate change is linked to changes in:1. Habitat. As flooding by rising sea levels will destroy valuable coastal ecosystems

2. Weather changes. Wind patterns, rain fall and seasonal changes will lead to some species finding it hard to survive in their existing ecosystem.

3. Migration patterns. As climates become hotter and colder migrating patterns of birds, insects and mammals could change as their previous locations become inhospitable

4. Reduced biodiversity. Extinction is a major threat to many species that live in areas which will suffer the greatest change. For example, polar bears are at risk if the ice melts.


178. Name the waste gases made by burning coal is a power station179. What gas is made in large amounts from farming cattle? 180. Which gas produces acid rain?181. What is smog and what are it’s effects?182. Name the two greenhouse gases that forms a layer in the atmosphere183. Why can’t the sun’s radiation leave the Earth’s atmosphere?


184. In the last 200 years the concentration of carbon dioxide in the Earth’s atmosphere has risen.

Explain how a rise in carbon dioxide concentration in the atmosphere can decrease biodiversity.

185. Scientists have observed changes in the migration patterns of some species of birds.

The graph shows the arrival dates in the UK of two species of birds, the Sand martin and the Barn swallow.

Both birds feed on flying insects.

(a) Give two changes in migratory patterns shown in the data.

(b) Suggest reasons for the change in the migration pattern of the Sand martin.

3. The figures below show the levels of carbon dioxide in air from 150 000 years ago.

TIME CARBON DIOXIDE CONCENTRATION

1500 years ago 270 parts per million

1800 AD 290 parts per million

1957 315 parts per million

1983 340 parts per million

(a) Explain why carbon dioxide levels in the atmosphere are changing.

(b) It is suggested that the increased level of carbon dioxide in the air is causing the atmosphere to warm up (the “Greenhouse Effect”).

Describe, as fully as you can, two major effects of global warming and how these may affect the human population.

186. Human activities can affect our ecosystem.

The graph shows information about how the area of ocean with sea ice in the arctic has changed between 1979 and 2016.

(a) Give two conclusions you can make from the data shown in the graph.

(b) The area of ocean with sea ice in the arctic has changed. Most scientists believe this is due to the activities of humans.

Explain the activities of humans that have led to the changes in sea ice from 1979 to 2016.

Part 11 Trophic levels in an ecosystem (triple only)

As you will recall from previous studying of Biology, Organisms exist in food chains and food webs. Each level on a food chains (producer, primary consumer, secondary consumer etc..) is known as a trophic level. Trophic levels can be represented by numbers as follows:

Level 1: Plants and algae make their own food and are called producers. Level 2: Herbivores eat plants/algae and are called primary consumers. Level 3: Carnivores that eat herbivores are called secondary consumers. Level 4: Carnivores that eat other carnivores are called tertiary consumers.

Apex predators are carnivores with no predators. Decomposers break down dead plant and animal matter by secreting enzymes into the environment. Small soluble food molecules then diffuse into the microorganism.Comprehension questions – each question should be attempted first from memory. Every five questions get your green pen and use the text to check your answers.

187. Define ‘producer’ in terms of food chains188. What is a herbivore? Give two examples189. What is a carnivore? Give two examples190. What is a trophic level?191. What is the difference between a tertiary consumer and a secondary

consumer?192. What trophic level will a duck be on? Give a reason for your answer.193. What is a apex predator? Give an example194. What are decomposers? Give two examples


195. Boris says “all organism that are tertiary consumers must be herbivores”. Is he correct? Explain your answer

196. True of false: There is always a 4th trophic level. Explain you answer.197. (prior knowledge) What cell organelle must be present in all producers?

Give a reason for your answer.198. Complete the sentences below in your book

Decomposers are vital to the survival of all life on the planet because…Decomposers are vital to the survival of all life on the planet but…Decomposers are vital to the survival of all life on the planet so…

Pyramids of biomass

Biomass is the mass of all the organisms in a particular area. When we look at the biomass of the different trophic levels of a food web we notice that as you move up the trophic levels the biomass decreases. This is best visualised in a pyramid of biomass. In a pyramid of biomass, the trophic levels increase as you go up the pyramid. The width of the bars shows the total biomass for that trophic level. The diagram to the right shows how the pyramid of biomass, the food chain and the trophic level are related.

Why is there always less biomass as you go up the trophic levels?Explaining why this shape is always found needs us to understand the point of feeding. When we study producers, we notice that most of the energy from the sun does not get converted to biomass. Only about 1% of the sun’s energy is captured. The rest is either the wrong frequency, is reflected or misses the leaf completely. Feeding is all to do with transferring energy from the food into the organism eating the food. But the food does not just sit around waiting to be eaten. It is constantly respiring, moving, reproducing and excreting. All these processes require the transfer of energy and often transfer waste energy as heat to the

surroundings. All this energy is not converted into new biomass by growth so cannot be passed up the trophic levels. As a rule only 10% of the energy is passed up the trophic levels of a food chain or web.


178. The sun shines 1000J on a patch of grass. How many Joules of energy are transferred into biomass?

179. What percentage of the energy is lost between the moose and the lion (which for the record do not live in the same continent)?

180. List the ways energy is transferred that do not cause biomass to be made.181. Which living process does cause biomass to be increased? 182. (prior knowledge) What are the two waste products from respiration?183. (prior knowledge) What organelle is in all cells and the site of respiration?


184. A field of grass has a store of 1x105 joules of energy. A herd of cows feed on the field. Calculate the maximum amount of energy that can be transferred to the herd. Give your answer in standard form.

185. Joe, a zookeeper, buys the herd of cows in the Q above to feed his tigers. Calculate the maximum energy that can be transferred to his tigers. Give your answer in standard form.

186. A fox gains 15J from eating a chicken. The chicken ate corn. The corn gained its energy from the sun. Using the rule we have discussed calculate the amount of energy that was shone on the corn by the sun.

187. The diagram below shows a food chain in a river.

(a) Draw one line from each scientific term to the correct organism in the food chain.

Scientific term Organismin the food chain

Algae

Apex predator

Invertebrate animals

Primary consumer

Large fish

Producer

Small fish

(b) The table below shows the biomass of the organisms at each stage in the food chain.

Organism Biomass in arbitrary units

Algae 840

Invertebrate animals 200

Small fish 40

Large fish 10

Calculate the percentage of the biomass of the invertebrate animals that is transferred to the large fish.

Use the equation:

(c) A large amount of biomass is lost from the food chain.

Complete the sentences.

Choose answers from the box.

coordination digestion excretion

filtration ingestion respiration

When the small fish eat the invertebrate animals, not all of this material is

broken down during _________________________ .

Materials absorbed from the gut may enter the body cells of the small fish.

These materials are broken down into carbon dioxide and

water by _________________________ .

The carbon dioxide and other waste materials from the body cells are removed

from the small fish by _________________________ .

(d) A disease kills many of the small fish.

Why does the number of invertebrate animals increase?188.

Figure 1 shows:• a food chain for organisms in a river• the biomass of the organisms at each trophic level.

Figure 1

(a) Draw a pyramid of biomass for the food chain in Figure 1 on Figure 2.

You should:• use a suitable scale• label the x-axis• label each trophic level.

Figure 2

(b) Calculate the percentage of the biomass lost between the algae and the large fish.

Give your answer to 2 significant figures.

(c) Give one way that biomass is lost between trophic levels.

189.

Food chains show the flow of energy through the organisms in a habitat.

(a) The diagram below shows a food chain.

grass sheep human

The biomass in each stage of the food chain changes as food passes along the food chain.

Draw a pyramid of biomass for this food chain.

Label the pyramid.

(2)

(b) The table below shows three food chains, A, B and C.

Food chain

A plants sheep human

B plants grasshoppers frogs trout human

C plants human

(i) In which food chain, A, B or C, will the greatest proportion of

biomass and energy of the plants be passed to humans? (1)

(ii) Give reasons why the food chain that you chose in part (b)(i) passes on the greatest proportion of biomass and energy to humans.

190.

The photographs show a food chain from a seashore. The photographs are not to the same scale.

© Getty Images/ © Paul Williamson/iStock/ © twobluedogs/iStock/ © Gabriela Insuratelu/ Thinkstock Thinkstock Thinkstock iStock

Students estimated the population and biomass of each of the organisms on part of a seashore.

The table shows the students’ results.

Organism Population Mean mass of oneorganism in grams

Biomass ofpopulation in

grams

Seaweed 50 4000 200 000

Limpet 1200 30 36 000

Crab 100 90 9 000

Gull 2 900

(a) (i) Use the data in the table to calculate the biomass of the gull population.

(ii) Draw a pyramid of biomass for this food chain.Label the pyramid.

(b) The biomass of the crab population is much less than the biomass of the limpet population.

Suggest two reasons why.

191. Students investigated a food chain in a garden.

lettuce → snail → thrush (bird)

The students:• estimated the number of lettuce plants in the garden• estimated the number of snails feeding on the lettuces• counted two thrushes in the garden in 5 hours.

The table below shows the students’ results and calculations.

Organism Population size

Mean mass of

each organism

in g

Biomass of population

in g

Biomass from

previous organism

that is lost in g

Percentage of biomass

lost

Lettuce 50 120.0 6000

Snail 200 2.5 500 5500 91

Thrush 2 85.0 170 330 66

(a) (i) Give two ways that biomass is lost along a food chain.

(ii) Scientists estimate that about 90% of the biomass in food is lost at each step in a food chain.

Suggest one reason why the students’ value for the percentage of biomass lost between the snails and the thrushes is only 66%.

(b) European banded snails have shells with different colours (light or dark) and with stripes or with no stripes.

Figure 1 shows two examples of European banded snails.

Figure 1

© Eric Lsselee/iStock © filipfoto/iStock

Figure 2 shows results from surveys in woodlands and in grasslands of the percentage of snails with light-coloured shells and the percentage of snails with no stripes.

Each point on the graph represents the results of one survey in one habitat.

Figure 2

(i) Figure 2 is a scatter graph.

Why is a scatter graph used for this data?

(ii) Compare the general appearance of snails that live in woodlands with the general appearance of snails that live in grasslands.

(iii) Suggest a reason for the general appearance of snails that live in woodlands.

192. The diagram shows the annual energy flow through 1 m2 of a habitat.

The unit, in each case, is kJ per m2 per year.

(a) Calculate the percentage of the energy absorbed by the grass from sunlight that is transferred to the frog.

Show clearly how you work out your answer.

(c) All of the energy the grass absorbs from the sun is eventually lost to the surroundings.

In what form is this energy lost?

(c) Food chains are usually not more than five organisms long.

Explain why. To gain full marks you must use data from the diagram.

(d) In this habitat microorganisms help to recycle materials. Explain how.

Part 12 Food security (Triple only)Food security is having enough food to feed a population.Biological factors which are threatening food security include:

The increasing birth rate has threatened food security in some countries As the global population grows there are more people to feed. Not all countries can grow enough food to feed their population. If the country is rich then it will be able to buy food to be imported, but poorer countries cannot do this.

Changing diets in developed countries means scarce food resources are transported around the world

People in the UK have developed more global tastes. The avocado for example needs to be imported. To provide summer fruits all year round they are imported from the southern hemisphere when we are in winter.

New pests and pathogens that affect farmingFusarium fungus is attacking Banana plants greatly reducing the available crops.

Environmental changes that affect food production, such as widespread famine occurring in some countries if rains fail

In the 1983-1985 Ethiopia suffered record low rainfall. This resulted in a devastating famine that killed 1.2 million people.

The cost of agricultural inputs

To make fields fertile all year-round farmers spread fertilisers, pesticides and herbicides. These cost money, but also have an environmental cost in terms of reduced biodiversity.

Conflicts that have arisen in some parts of the world which affect the availability of food and water

South Sudan has suffered famine due to the constant civil war that has waged since 2011.One of the early ways of increasing food production was to use factory farming. To increase the rate of growth animals are kept in close confinement and over fed. This allows for a large amount of food to be grown in a small space. By reducing movement less energy is wasted and more growth occurs. An increasing number of people are now against factory farming due to the way it treats the animals.Sustainable methods must be found to feed all people on Earth. These could include improvements in agricultural technology, changes to peoples eating habits and genetically modified crops which can grow in more food in hostile conditions.The fungus fusarium is one possible solution. It can be grown in vats of glucose syrup as long as oxygen is pumped in. This means that it can produce a large amount of biomass in a short time and a small space. The fungus provides a source of protein called mycoprotein which is suitable for vegetarians. Golden rice is a genetically modified organism (GMO) which can produce beta-carotene, which can be used by the body to make vitamin A. This rice will prevent vitamin A deficiency which can affect the eyes, skin and rate of growth. GMO’s are controversial as some people believe that food should not be altered as it might have unforeseen circumstances. Scientists are confident that they have tested the foods well and they show no signs of being dangerous for consumption or the ecosystem.Comprehension questions – each question should be attempted first from memory. Every five questions get your green pen and use the text to check your answers.

193. What is food security?194. Why does the world need to produce more food each year than the year

before?195. Why might pests be a threat to food security?196. Give two possible reasons for famine197. What is a GMO?198. Give two ways GMOs can help improve food security?199. What do farmer add to fields to increase food production?200. Quorn is a brand of meat free mycoprotein. What is it made from?201. What are the two conditions needed in the vats to make Quorn?


202. Mycoprotein is a protein-rich food. Mycoprotein is made from the fungus Fusarium. The diagram below shows a fermenter used for growing Fusarium.

(a) Explain why the fermenter is sterilised before use.

(b) Cold water is pumped through the cooling coil at point X.

This maintains a constant temperature inside the fermenter.

Suggest the temperature at which Fusarium grows fastest.Choose from 5oC, 20 oC, 30 oC, 85 oC

(c) Glucose and bubbles of air enter the fermenter.

The bubbles of air supply oxygen. Explain why Fusarium needs glucose and oxygen.

(d) The bubbles of air also move materials around the fermenter.

Suggest why it is useful for bubbles of air and materials to move around inside the fermenter.

(e) 100 grams of chicken meat contains 22 grams of protein.

100 grams of mycoprotein contains 11 grams of protein.

A man ate 100 grams of chicken in one meal.

How many grams of mycoprotein would the man need to eat to get the same mass of protein as in 100 grams of chicken?

203. The number of fish in the oceans is decreasing.

The table below shows information about the mass of fish caught by UK fishermen between 2002 and 2010.

Year

Mass of fish caught byUK fishermen from

ALL SOURCESin thousands of

tonnes

Mass of fish caught byUK fishermen from

SUSTAINABLE SOURCES

in thousands of tonnes

Percentage offish caught from

sustainablesources

2002 690.0 427.8 62.0

2004 655.0 396.6 60.5

2006 619.0 386.0 62.4

2008 589.0 436.1 74.0

2010 611.5 465.0

(a) (i) Calculate the percentage of fish caught from sustainable sources in 2010.

(ii) Describe the pattern in the table above for the mass of fish caught from all sources.

Suggest reasons for this pattern.

(iii) Suggest why the percentage of fish caught from sustainable sources is increasing.

(b) Give two methods of maintaining fish stocks at a sustainable level.

(c) The image below shows a fish farm.

© debsthelio/iStock/Thinkstock

In a fish farm, large numbers of fish are grown in cages in the sea.

Why do fish in the cages grow faster than fish of the same species that are free in the sea?You should refer to energy in your answer.

204. Tomatoes are grown in greenhouses in the UK and outdoors in the UK and the Canary Islands.

The chart shows in which months these tomatoes can be bought in shops in the UK.

The Canary Islands are about 3000 km from the UK. Some people prefer to buy tomatoes grown in the UK. What are the advantages and disadvantages of buying tomatoes grown in the UK, instead of buying tomatoes grown in the Canary Islands?

205. A fish farmer keeps trout in a large net in a lake.

The fish farmer feeds the trout on food made from soya beans.

When the trout are large enough the farmer sells them for food for people.

(a) Draw a pyramid of biomass for the three organisms in this food chain. Label the pyramid.

(b) It would be more energy efficient if people ate the soya beans rather than eating the trout. Suggest two reasons.

(c) Suggest one advantage to the fish farmer of keeping the trout in a large net instead of letting them swim freely in the lake.

(d) Some trout die before they are large enough to be sold.The dead trout contain carbon. Use your knowledge of the carbon cycle to describe how this carbon is returned to the atmosphere after the trout die.

206. The diagram shows what happens to some of the energy in the food that a chicken eats.

(a) Calculate the percentage of energy used for growth.

Show clearly how you work out your answer.

(b) The energy that is not transferred into growth is lost. Give three ways in which this energy is lost.

(c) The pictures show two ways of keeping chickens to produce eggs.

Battery chickens produce more eggs per year than free-range chickens. Suggest one reason why.

(d) The animals that we raise for food are usually herbivores (plant eaters) rather than carnivores (flesh eaters). Explain why.

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