Feeding Relationships (Edexcel IGCSE Science (Double Award): Biology)

The diagram shows part of a food web for a desert community.

(i) How many organisms in this food web are secondary consumers?

(1)

(ii) Draw the longest food chain in this food web.

(1)

(iii) Explain why most of the energy in the producers is not transferred to the hawk.

(3)

The photograph shows a fennec fox.

Drew Avery, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons

Fennec foxes live in the Sahara Desert, which is very hot. They have very large ears and a thin body.

Explain how the body shape of the fennec fox has evolved by natural selection.

The plants in a woodland are eaten by mice and caterpillars.

The mice also eat the caterpillars.

The mice are eaten by birds called owls.

Draw a food web showing these feeding relationships.

Give the term that describes the trophic level of a caterpillar.

The woodland covered a total area of 5 km².

A scientist investigates the number of mice and owls in the woodland.

He counts the number of mice and owls on the same summer day each year for five years.

The table shows the scientist’s results.

(i) Calculate the number of mice in the total area of woodland in year 3.

(2)

(ii) Suggest why there were more mice in year 4 than in the other years.

(3)

(iii) Suggest why the number of owls was fairly constant each year.

(2)

(iv) Suggest a method you would use to estimate the number of mice in the woodland.

(3)

A student studies the organisms in a pond community.

Which of these is the correct description of a community?

The table shows the number of organisms per m² at different trophic levels in a pond community.

It also shows the total biomass of these organisms per m².

(i) Calculate the mean mass in g of a single primary consumer.

Give your answer in standard form.

(3)

(ii) Use the grid to draw a pyramid of biomass for the pond community.

(2)

The number of secondary consumers is low because energy transfer is not 100 % efficient.

(i) Explain why egestion is one reason why energy transfer is not 100 % efficient.

(2)

(ii) Give two other reasons why energy transfer is not 100 % efficient.

(2)

Pyramids of biomass and energy transfer are ways of representing what happens in an ecosystem.

Diagram 1 shows pyramids of biomass for a crop field ecosystem and for a coral reef ecosystem.

(i) Use data from Diagram 1 to calculate the efficiency of the transfer of biomass from producers (P) to primary consumers (C1) in the coral reef.

(1)

(ii) The efficiency of the transfer of biomass from primary consumers (C1) to secondary consumers (C2) in the crop field is 1%.

Calculate the biomass of the secondary consumers in the crop field in g per m².

(1)

(iii) Suggest why the biomass transfer is different in the coral reef compared to the crop field.

(1)

Diagram 2 shows pyramids of biomass for an ocean and a lake.

Explain the shape of the pyramid of biomass for the ocean.

The diagram shows a food web from a woodland ecosystem.

(i) Which organism in the food web is the producer?

(1)

(ii) Which organism acts as both a secondary consumer and a tertiary consumer in the food web?

(1)

The amount of energy transferred changes as you move along a food chain.

The data comes from an ecosystem containing producers, primary consumers and secondary consumers.

(i) The light energy reaching the producers is 7.1 × 10⁶ kJ per m² per year.

Explain why the plants cannot absorb all of this energy.

(2)

(ii) The table shows that energy is transferred between producer and primary consumer and between primary consumer and secondary consumer.

A student states that the energy transfer between producer and primary consumer is the most efficient.

Determine whether the student’s statement is correct.

(2)

Woodlice feed on dead and decaying plant material in the soil. The photographs show how a woodlouse can curl up into a ball.

This behaviour is an example of a reflex response.

Franco Folini, CC BY-SA 3.0 <http://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons

DinaKuzia, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons

(i) State what is meant by a reflex response.

(1)

(ii) Give a reason why this reflex response benefits the woodlouse.

(1)

(iii) Describe how this reflex response could have evolved by natural selection.

(4)

The diagram shows a food chain in the Antarctic ocean.

(i) Which term describes the trophic level of the krill?

(1)

(ii) Draw a labelled pyramid of biomass to represent this food chain.

(2)

The microscopic plants float in seawater, but also grow on the lower surface of ice.

The krill feed on the microscopic plants.

They remove microscopic plants from the lower surface of the ice at a rate of 1.6 cm² per second.

Calculate the time taken for the krill to remove microscopic plants from one square metre of ice.

Give your answer in minutes.

A student investigates the rate that krill feeding removes microscopic plants floating in seawater.

Suggest how the student could do this investigation in a laboratory.

Krill obtain most of their food from microscopic plants growing on the lower surface of ice.

Explain how global warming could affect the whale population in the Antarctic ocean.