Trophic levels

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.

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.

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.

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?