Pyramids of number, biomass & energy

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.

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.

People eat fish caught in the North Sea. Figure 4 shows a food chain.

The algae make glucose by photosynthesis. Which two substances do the algae need for photosynthesis?

Tick (✓) two boxes.

What is the source of energy for photosynthesis?

Tick (✓) one box.

Which pyramid of biomass is correct for the food chain shown in Figure 4 ?

Tick (✓) one box.

Figure 5 shows the biomass of adult herring in the North Sea between

1950 and 1990.

Too many herring were caught in the 1960s. Calculate the percentage decrease in the biomass of adult herring between 1960 and 1970. Use the equation:

Give your answer to the nearest whole number.

From 1977, laws were introduced to help conserve herring.

Describe the change in biomass of adult herring from 1977 to 1990. Use data from Figure 5 in your answer.

One of the laws was to control mesh size of fishing nets. Figure 6 shows a fishing net with a legal mesh size.

Herring can live for up to 12 years. Herring start to reproduce when they are 3 to 4 years old. Explain how the control of mesh size of fishing nets has helped to conserve stocks of herring.

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 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.