Transfer of biomass

Different species in a habitat may depend on each other for food.

Several food chains may be linked together to form a food web.

Figure 10 shows a food web in a lake.

Most organisms in the food web get their energy by eating other organisms.

Where does the pondweed get energy from?

Tick (✓) one box.

Name one organism from Figure 10 that is a primary consumer.

There are four trophic levels in Figure 10.

Which is the correct pyramid of biomass for the food web in Figure 10 ?

Tick (✓) one box.

One of the food chains in Figure 10 is:

10% of the biomass in each trophic level is transferred to the next trophic level.

What percentage of the biomass in the algae is transferred to the fish?

Tick (✓) one box.

What are two ways that energy is lost from organisms in the food chain?

Tick (✓) two boxes.

Scientists counted the number of fish, snails and worms in a sample taken from the lake.

Table 3 shows the results.

Peat bogs are estimated to contain twice as much carbon as all the world’s forests.

Figure 2 shows a section through part of a peat bog.

Layer A contains a lot of air.

Layer B:

• contains the dead remains of plants

• has a low pH

• contains very little oxygen

• contains carbon dioxide and methane.

Explain why most of the dead remains of plants in layer B do not decay.

The peat bog in Figure 2 is a stable community.

The moss produces biomass at a rate of 340 g/m²/year.

What is the approximate biomass of the moss that becomes biomass in primary

Tick () one box.

The sundew plant shown in Figure 2 on page 4 has leaves with sticky hairs that

trap and digest insects.

Digestion of the insects releases phosphates and simple compounds of nitrogen that are used by the sundew plant.

What substance can the sundew plant make using the phosphates ?

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What substance can the sundew plant make using the nitrogen ?

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Humans have destroyed large areas of peat bog to collect peat.

The peat provides fuel and provides compost for gardeners to use.

The peat comes from layer B in Figure 2 on page 4.

Layer B:

• contains the dead remains of plants

• has a low pH

• contains very little oxygen

• contains carbon dioxide and methane.

Figure 3 shows the removal of peat from a peat bog.

Explain how the destruction of peat bogs and the use of peat affects the temperature of the Earth’s atmosphere.

Farmers can increase the growth rate of farm animals by controlling the animals’ diets.

A farmer has 1000 chickens.

• The farmer feeds the chickens on seeds from maize plants.

• 1 hectare of land produces 16.4 tonnes of maize seeds.

• The maize seeds have an energy content of 16 MJ per kg.

• Chickens can use 80% of the energy in maize seeds.

• Each chicken needs 46 MJ of energy to grow to full size.

Calculate the area of land needed to provide enough energy from maize seeds for 1000 chickens to grow to full size.

Give your answer in m².

Give your answer to 3 significant figures.

1 tonne = 1000 kg

Another farmer produced 4200 kg of maize seeds in a field.

The farmer fed the maize to 1000 chickens.

At full size, the mean mass of one chicken was 2.2 kg.

Complete Figure 11 to show a pyramid of biomass for the food chain from the maize seeds to 1000 chickens.

You should:

• label the x-axis

• use a suitable scale.

Calculate the ratio of chicken biomass to maize seed biomass.

Use data from Question 07.2.

Give your answer in its simplest form.

Chickens can use 80% of the biomass from the maize seeds they eat for respiration and growth.

What happens to the remaining 20% of the biomass in the maize seeds?

Protein is an important part of a chicken’s diet.

• Proteins contain 20 different types of amino acid.

• A chicken can make many of the 20 amino acids from other substances in the diet.

• Essential amino acids are amino acids the chicken cannot make.

• Essential amino acids must be included in the diet.

Maize seeds contain protein but the proportion of some essential amino acids is low.

Scientists have produced a type of maize called Quality Protein Maize (QPM).

Table 2 compares the proportions of seven essential amino acids in normal maize seeds and in QPM seeds.

Which amino acids are found in significantly higher proportions in the QPM seeds?

Tick () one box.

Table 2 shows that 1 kg of QPM contains less leucine than 1 kg of normal maize.

Suggest why a diet containing less leucine does not slow down the growth of chickens.

Different species in a habitat may depend on each other for food.

Figure 3 shows a food chain.

The grass needs energy to grow.

What is the source of energy for the grass?

Table 2 lists different types of feeding relationship.

Write the name of one organism from Figure 3 in each box in Table 2.

Each organism may be written in one box or in more than one box.

The first box has been completed for you.

Figure 4 shows the appearance of the snowshoe hare in the summer and in the winter.

Figure 4

Snowshoe hare in summer
Snowshoe hare in winter

The snowshoe hare has a different fur colour in the summer than in the winter.

Explain how the different fur colour increases the chance of survival of the snowshoe hare.

Figure 5 shows how the number of snowshoe hares and the number of lynx varied in one area between 1900 and 1935.

Figure 5 shows that the number of snowshoe hares and the number of lynx increase and decrease several times.

Suggest two reasons why the number of snowshoe hares increases.

The number of snowshoe hares increased and decreased four times between 1900 and 1935.

What effect does an increase in the number of snowshoe hares have on the number of lynx?

Suggest one reason why the number of lynx decreased from 1915 to 1919.

Use information from Figure 5.

When the snowshoe hare eats grass, about 90% of the biomass of the grass is lost.

Give two ways the biomass is lost.

Energy flows through an ecosystem and materials are recycled. Figure 6 shows the water cycle.

Name process X.

Name the process by which water is absorbed into plant roots.

Give two uses of water in plants.

Figure 7 shows the flow of energy through a food chain. The numbers are in kilojoules/m²/year.

The cow is more efficient than the grass at converting energy. The energy conversion efficiency of the cow is 4.098%. Calculate how many times more efficient the cow is at converting energy than the grass. The equation for energy conversion efficiency is:

Give your answer to 3 significant figures.

Number of times (3 significant figures) =

It is more energy-efficient to rear cows indoors than to rear cows outdoors. Give two reasons why.

Suggest two possible disadvantages of rearing cows indoors.

A food web contains several food chains. Figure 9 shows a food web.

The animals in Figure 9 get their energy by eating other organisms. Describe how the algae get energy.

Name one primary consumer in Figure 9.

Name one producer in Figure 9.

The different food chains in Figure 9 have different numbers of organisms. Complete Figure 10 to show a food chain in Figure 9 with five organisms, including the human.

Figure 9 shows that mackerel eat krill and squid. The biomass of mackerel is much less than the combined biomass of krill and squid. One reason for this is that the mackerel cannot digest all parts of the krill and squid. Give two other reasons.

Figure 11 shows how the biomass of adult herring in the North Sea has changed

between 1950 and 2010.

Calculate the percentage decrease in the biomass of herring between 1960 and 1977. Give your answer to the nearest whole number.

Too many herring were caught by fishermen between 1960 and 1977. Herring can live for up to 12 years and begin to reproduce when 3 to 4 years old. Laws have been introduced to help conserve herring:

• 1977 to 1981 – herring fishing was banned in the North Sea

• 1984 to present day – control of mesh size of fishing nets

• 1997 to present day – fishing quotas were introduced

• 1998 to present day – herring fishing was banned in breeding grounds during the breeding season.

Figure 12 shows how a minimum mesh size helps to conserve herring.

Figure 11 is repeated below.

Evaluate the effect of these laws on the conservation of herring stocks.

Use data from Figure 11 and information from Figure 12 in your answer.

A food for pet dogs contains meat from chickens.

Figure 1 shows the food chain.

What is the trophic level of the dog?

Tick (✓) one box.

Draw one line from each organism to the description of the organism’s position in the food chain.

Name the process wheat plants use to make glucose.

Some of the chicken biomass does not become part of the dog’s biomass.

What is one reason why?

Tick (✓) one box.

A new dog food has been developed.

The new dog food is made from insects.

The insects in the dog food factory are fed on vegetables.

Which pyramid of biomass represents the vegetables, insects and dogs in this food chain?

Tick (✓) one box.

Beef from cows is used to make some dog food.

Cows release methane.

The company that makes dog food from insects made the statement:

‘Dog food made from insects is more sustainable than dog food made from beef.’

Which are two reasons that support the company’s statement?

Tick (✓) two boxes.

A new dog food has been developed that does not contain meat from cows, sheep or chickens. The new dog food contains insects. The insects in the dog food factory are fed on waste vegetables.

Sketch the pyramid of biomass for the food chain that produces food for dogs from insects. Label the pyramid.

Describe two reasons why the biomass of the insects eaten by dogs does not all become biomass of the dogs.

Explain how making dog food from insects could improve human food security in the future.

Figure 14 shows a food chain in a pond.

Which term describes the Daphnia in this food chain?

Tick (✓) one box.

Draw a pyramid of biomass for the food chain.

Label each trophic level.

Give one reason why the total biomass of the Daphnia in the pond is different from the total biomass of the algae.

Students investigated the size of the population of Daphnia in the pond.

This is the method used.

1. Collect 1 dm³ of pond water from near the edge of the pond.

2. Pour the water through a fine net.

3. Count the number of Daphnia caught in the net.

4. Repeat steps 1–3 four more times.

Table 3 shows the results.

Calculate the mean number of Daphnia in 1 m³ of pond water.

The pond was a rectangular shape, measuring:

• length = 2.5 metres

• width = 1.5 metres

• depth = 0.5 metres.

Calculate the estimated number of Daphnia in the pond.

Use your answer from Question 07.4.

Give your answer in standard form.

Rainfall can cause fertiliser to be washed from farmland into a pond.

The students investigated the effect of fertiliser on the population of Daphnia in water from the pond.

• The students put 20 Daphnia in each of five different concentrations of fertiliser.

• The students counted the total number of Daphnia in each concentration of fertiliser after 2 weeks.

Figure 15 shows the results.

A concentration of 5.0 mg/dm³ of fertiliser caused a large increase in the population of Daphnia.

Explain why.

Figure 14 is repeated below.

The population of Hydra will decrease when 20 mg/dm³ of fertiliser is added to the pond.

Explain why.

Figure 1 shows a food chain in a pond.

Which term describes the Daphnia in this food chain?

Tick (✓) one box.

Draw a pyramid of biomass for the food chain.

Label each trophic level.

Give one reason why the total biomass of the Daphnia in the pond is different from the total biomass of the algae.

Students investigated the size of the population of Daphnia in the pond.

This is the method used.

1. Collect 1 dm³ of pond water from near the edge of the pond.

2. Pour the water through a fine net.

3. Count the number of Daphnia caught in the net.

4. Repeat steps 1–3 four more times.

Table 1 shows the results.

Calculate the mean number of Daphnia in 1 m³ of pond water.

The pond was a rectangular shape, measuring:

• length = 2.5 metres

• width = 1.5 metres

• depth = 0.5 metres.

Calculate the estimated number of Daphnia in the pond.

Use your answer from Question 01.4.

Give your answer in standard form.

Rainfall can cause fertiliser to be washed from farmland into a pond.

The students investigated the effect of fertiliser on the population of Daphnia in water from the pond.

• The students put 20 Daphnia in each of five different concentrations of fertiliser.

• The students counted the total number of Daphnia in each concentration of fertiliser after 2 weeks.

Figure 2 shows the results.

A concentration of 5.0 mg/dm³ of fertiliser caused a large increase in the population of Daphnia.

Explain why.

Figure 1 is repeated below.

The population of Hydra will decrease when 20 mg/dm³ of fertiliser is added to the pond.

Explain why.

Figure 1 shows a food chain in a river.

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

Organism Scientific term

Table 1 shows the biomass of the organisms at each stage in the food chain.

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

Use the equation:

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

Complete the sentences.

Choose answers from the box.

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

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

These materials are broken down into carbon dioxide and

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

A disease kills many of the small fish.

Why does the number of invertebrate animals increase?

Figure 8 shows:

• a food chain for organisms in a river

• the biomass of the organisms at each trophic level.

Biomass in g/m²: 840
200 40 10

Draw a pyramid of biomass for the food chain in Figure 8 on Figure 9.

You should:

• use a suitable scale

• label the x-axis

• label each trophic level.

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

Give your answer to 2 significant figures.

Give one way that biomass is lost between trophic levels.

A large amount of untreated sewage entered the river. Many fish died.

Untreated sewage contains organic matter and bacteria.

Explain why many fish died.