Energy in ecosystems

Figure 13 shows the biomass of each population of organisms in a food chain.

Figure 13

Calculate the percentage efficiency of biomass transfer from the aphids to the ladybirds.

Use the equation:

Give your answer to the nearest whole number.

Give two reasons why the biomass of ladybirds is lower than the biomass of aphids in this food chain.

Aphids are a problem for rose growers as they damage the leaves of rose plants.

Explain how ladybirds could be used to reduce the number of aphids.

As human population rises, food security is an increasing problem throughout the world.

Give three factors that reduce the amount of food available for humans throughout the world.

Figure 4 shows a food chain in an oak woodland.

oak tree aphids ladybirds robins

State what the arrows in the food chain represent.

A robin in this woodland eats 6 g of food in a day.

The robin uses 15% of this food for growth.

Calculate the mass of food that is used for growth.

Temperatures in England have increased over the last 20 years.

State two human activities that have caused this temperature increase.

One new species of moth is now able to live in England because of the increased temperatures.

This moth feeds on oak leaves.

Explain how these moths may affect the number of aphids in the food chain shown in Figure 4.

A student investigated the decomposition of two different types of leaf.

The student placed 200 grams of holly leaves in a net bag.

The student placed 200 grams of oak leaves in another net bag.

The bags were left in a classroom.

The mass of the leaves in each bag was recorded every 10 days for 50 days.

State two variables that would need to be controlled in this investigation.

The results of this investigation are shown in Figure 16.

Calculate the rate of decomposition of holly leaves from 0 to 50 days.

Compare the trends shown in the data for holly leaves and oak leaves.

Explain why it is important for the environment that dead leaves are decomposed.

Name one type of organism that decomposes leaves.

Leaves are eaten by snails.

1 600 grams of leaves and 10 snails were kept in a container for one month.

A scientist measured the mass of the leaves and the mass of the snails at the start and end of one month.

Figure 17 shows the results.

Explain why the change in mass of the leaves is not the same as the change in mass of the snails.

4 A student investigated the decomposition of two different types of leaf. The student placed 200 grams of holly leaves in a net bag. The student placed 200 grams of oak leaves in another net bag. The bags were left in a classroom. The mass of the leaves in each bag was recorded every 10 days for 50 days.

(a) State two variables that would need to be controlled in this investigation.

(b) The results of this investigation are shown in Figure 4.

Figure 4

(i) Calculate the rate of decomposition of holly leaves from 0 to 50 days.

(ii) Compare the trends shown in the data for holly leaves and oak leaves.

(c) Explain why it is important for the environment that dead leaves are decomposed.

(d) Name one type of organism that decomposes leaves.

(e) Leaves are eaten by snails. 1 600 grams of leaves and 10 snails were kept in a container for one month. A scientist measured the mass of the leaves and the mass of the snails at the start and end of one month. Figure 5 shows the results.

Explain why the change in mass of the leaves is not the same as the change in mass of the snails.

Figure 13 shows part of a food web of organisms found in the cold Antarctic Ocean.

Which term describes phytoplankton in this food web?

Humans are removing large numbers of cod from the Antarctic Ocean.

State why the removal of cod could lead to a decrease in the numbers of squid and penguins.

Explain why the removal of cod could lead to an increase in the numbers of squid and penguins.

Figure 14 shows information about the biomass of some organisms in one part of the Antarctic Ocean.

Draw and label a pyramid of biomass for this food chain.

Seals are mammals.

Explain why the conversion of biomass from phytoplankton to shrimps is more efficient than the conversion of biomass from cod to seals.

Cod are being overfished in the Antarctic Ocean.

Suggest two actions that could be taken by humans to increase the number of cod in the Antarctic Ocean.

10 A student investigated the width of leaves on nettle plants growing in two areas next to a woodland. Figure 19a shows a nettle plant and Figure 19b shows a map of the woodland showing area A and area B. The woodland caused area A to be in the shade.

(Source: © Alila Medical Media/Shutterstock) Figure 19a Figure 19b The student measured the maximum width of leaves on five plants from each area. The student always measured one leaf from the fourth pair of leaves.

(a) Give one reason why the student always measured a leaf from the fourth pair of leaves.

(b) Figure 20 shows the results.

Figure 20

(i) Why did the student not include the circled width when calculating the mean for area B?

(ii) Explain the difference in the mean width of leaves in the shade and those in the sunlight.

(c) The student also studied some of the animals in areas A and B. The student saw caterpillars eating the leaves of some nettles. The student also saw a toad eating a large beetle. Large beetles eat ladybirds. Ladybirds eat caterpillars.

(i) Give the food chain for these feeding relationships.

(ii) Frogs also eat large beetles. Figure 21 shows the energy transferred between these animals.

Figure 21

Calculate the percentage efficiency of energy transfer from the large beetles to the frog.

(iii) Give two reasons why only some of the energy in the biomass of the large beetles is transferred to the biomass of the frog.

4 A student investigated the width of leaves on nettle plants growing in two areas next to a woodland. Figure 5a shows a nettle plant and Figure 5b shows a map of the woodland showing area A and area B. The woodland caused area A to be in the shade.

(Source: © Alila Medical Media/Shutterstock) Figure 5a Figure 5b The student measured the maximum width of leaves on five plants from each area. The student always measured one leaf from the fourth pair of leaves.

(a) Give one reason why the student always measured a leaf from the fourth pair of leaves.

(b) Figure 6 shows the results.

(i) Why did the student not include the circled width when calculating the mean for area B?

(ii) Explain the difference in the mean width of leaves in the shade and those in the sunlight.

(c) The student also studied some of the animals in areas A and B. The student saw caterpillars eating the leaves of some nettles. The student also saw a toad eating a large beetle. Large beetles eat ladybirds. Ladybirds eat caterpillars.

(i) Give the food chain for these feeding relationships.

(ii) Frogs also eat large beetles. Figure 7 shows the energy transferred between these animals.

Calculate the percentage efficiency of energy transfer from the large beetles to the frog.

(iii) Give two reasons why only some of the energy in the biomass of the large beetles is transferred to the biomass of the frog.

A student investigated fish food.

The student added some fish food to a blue liquid in a test tube.

The solution turned from blue to purple.

Use words from the box to complete the sentences.

The blue liquid was_........ solution.

The purple colour showed that the fish food contained_........ .

The blue solution may be harmful if swallowed.

Which procedure is a health and safety precaution needed for this investigation?

Fish eat fish food.

The fish food contains energy.

Some of this energy is used by the fish for growth.

Figure 6 shows this energy transfer.

Each square in Figure 6 represents 1 kJ of energy.

Calculate the percentage of energy from the fish food that has been used in the growth of fish.

Describe what happened to the fish food that was eaten but was not used in the growth of the fish.

Figure 24 shows the world human population from 1800 to 2015.

In 2015, 13% of the world human population were classified as malnourished.

Calculate, using Figure 24, how many people were classified as malnourished in 2015.

Protein is an important nutrient in meat.

Describe the laboratory test for protein.

Figure 25 shows the mass of meat eaten in the world from 1980 to 2010.

Calculate the rate of increase in the mass of meat eaten in the world from 2000 to 2010.

_........ millions of tonnes per year

Figure 26 shows an energy pyramid.

Explain why the area labelled cattle is smaller than the area labelled plants.

The World Health Organisation uses this definition of food security.

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

Figure 7 shows the world human population from 1800 to 2015.

In 2015, 13% of the world human population were classified as malnourished.

Calculate, using Figure 7, how many people were classified as malnourished in 2015.

Protein is an important nutrient.

Describe the laboratory test for protein.

Figure 8 shows the mass of meat eaten in the world from 1980 to 2010.

Calculate the rate of increase in the mass of meat eaten in the world from 2000 to 2010.

_........ millions of tonnes per year

Figure 9 shows an energy pyramid.

Explain why the area labelled cattle is smaller than the area labelled plants.

The World Health Organisation uses this definition of food security.

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

Figure 8 shows an area of nettle plants.

Grass does not grow among the nettles.

Explain why grass does not grow where there are nettles.

Figure 9 shows caterpillars eating nettle leaves.

A caterpillar has a body mass of 6.0 grams. One week later, its body mass had increased to 7.5 grams. Caterpillars convert 10% of food eaten into body mass.

Calculate the mass of nettles that the caterpillar ate.

Describe what happens to food eaten that is not converted into the body mass of the caterpillar.

Devise a method a scientist could use to investigate how temperature affects nettle growth.

Since 2003, in France, people have been buying Siberian chipmunks as pets but then releasing them into the wild when they are no longer wanted.

They are now classified as an invasive species.

Figure 25 shows a Siberian chipmunk (Tamias sibiricus).

Figure 25

Siberian chipmunks eat acorns, which are the seeds of oak trees.

In Siberia, the natural predators of Siberian chipmunks are wild dogs.

Figure 26 shows the biomass of three organisms in a food chain from one area of Siberia.

Draw a pyramid of biomass for this food chain.

In France, Siberian chipmunks have very few natural predators.

Describe how this affected the Siberian chipmunk population in France.

The percentage of energy transferred from the acorns to the chipmunks is 9.5%.

The energy contained in the acorns is 97 500 kJ.

Calculate the amount of energy transferred to the chipmunks.

Give your answer to the nearest whole number.

The black-legged tick (Ixodes scapularis) is a parasite that feeds on the blood of animals including Siberian chipmunks and humans.

The tick transmits the Lyme disease pathogen.

Figure 27 shows the number of cases of Lyme disease in humans in France in 2003 and 2015.

Calculate the percentage increase in the number of cases of Lyme disease in humans in France from 2003 to 2015.

Explain why there has been an increase in the number of cases of Lyme disease in humans in France.

Since 2003, in France, people have been buying Siberian chipmunks as pets but then releasing them into the wild when they are no longer wanted.

They are now classified as an invasive species.

Figure 7 shows a Siberian chipmunk (Tamias sibiricus).

Siberian chipmunks eat acorns which, are the seeds of oak trees.

In Siberia, the natural predators of Siberian chipmunks are wild dogs.

Figure 8 shows the biomass of three organisms in a food chain from one area of Siberia.

Draw a pyramid of biomass for this food chain.

In France, Siberian chipmunks have very few natural predators.

Describe how this affected the Siberian chipmunk population in France.

The percentage of energy transferred from the acorns to the chipmunks is 9.5%.

The energy contained in the acorns is 97 500 kJ.

Calculate the amount of energy transferred to the chipmunks.

Give your answer to the nearest whole number.

The black-legged tick (Ixodes scapularis) is a parasite that feeds on the blood of animals including Siberian chipmunks and humans.

The tick transmits the Lyme disease pathogen.

Figure 9 shows the number of cases of Lyme disease in humans in France in 2003 and 2015.

Calculate the percentage increase in the number of cases of Lyme disease in humans in France from 2003 to 2015.

Explain why there has been an increase in the number of cases of Lyme disease in humans in France.