IGCSEScienceEdexcelScience (Double Award) (Modular)Biology Unit 2Exam Questions5. Ecology & the EnvironmentFeeding Relationships

Feeding Relationships (Edexcel IGCSE Science (Double Award) (Modular): Biology Unit 2): Exam Questions

Exam code: 4XSD1

1 hour8 questions
Easy
Medium
Hard
1a
1 mark

The diagram shows a food chain from a lake.

Food chain diagram drawn vertically as four labelled boxes joined by arrows pointing upwards. From the bottom of the chain to the top: microscopic plants, then small fish, then large fish, then birds.

Name the primary consumer in this food chain.

How did you do?

1b
5 marks

The microscopic plants convert light energy into chemical energy.

(i) Describe the process that converts light energy into chemical energy.

[3]

(ii) Give two reasons why some of the energy in the microscopic plants is not transferred to the small fish.

[2]

How did you do?

1c
2 marks

The birds do not have teeth.

The fish they eat is initially crushed in part of their digestive system called a gizzard.

Suggest why crushing the fish in the gizzard helps the birds to digest the fish.

How did you do?

2a
6 marks

The diagram shows an ocean food web.

Food web diagram for an ocean habitat, with arrows pointing in the direction of energy flow. Bladderwrack has arrows to grey mullet and to flat winkle. Microscopic algae has arrows to limpet and to sea urchin. Flat winkle has an arrow to crab. Limpet has an arrow to lobster. Grey mullet has an arrow to common seal. Sea urchin has an arrow to herring gull. Crab has an arrow to herring gull. Lobster has an arrow to common seal.

(i) Name the producers in this food web.

[2]

(ii) Name two secondary consumers in this food web.

[2]

(iii) Draw a food chain from this food web that contains four organisms and includes the herring gull.

[2]

How did you do?

2b
5 marks

This food chain is found in the food web.

microscopic algae → limpet → lobster → common seal

(i) Sketch and label the pyramid of energy for this food chain.

[2]

(ii) Explain why the amount of energy available to the organisms changes along this food chain.

[3]

How did you do?

3a
1 mark

The image below shows a simple food web.

Food web diagram with arrows showing the direction of energy transfer. Plankton has an arrow to Shrimp. Shrimp has arrows to Cod, Squid and Penguin. Cod, Squid and Penguin each have an arrow to Seal.

Identify which of the following statements best describes secondary consumers in this food web.

  • Carnivores that eat herbivores.

  • Herbivores that eats producers.

  • Carnivores that also eat producers.

  • Apex predators.

Choose your answer

3b
1 mark

Identify which of the following pyramids correctly shows the pyramid of biomass for one of the food chains in the food web in part (a).

Four pyramids of biomass labelled A, B, C and D, each drawn as four stacked horizontal bars of differing widths. In A the bottom bar is a narrow stub, with the widest bar above it, then a narrower bar, then the narrowest bar at the top. In B the bottom bar is a narrow stub, then a medium bar, then the widest bar, then a narrow bar at the top. In C the bottom bar is the widest and each bar above it is narrower than the one below. In D the bottom bar is wide, the next is narrower, then a narrow stub, then the widest bar of all at the top.

    Choose your answer

    3c
    2 marks

    Explain why a food chain rarely has more than five trophic levels.

    How did you do?

    3d
    2 marks

    In the food web in part (a) the biomass of the producer (plankton) is 10 000 kg. Only 8 % of this biomass is passed to the shrimp and, of that, only 7 % is passed onto the penguin. 

    Calculate the biomass that is gained by the penguin in this food web. 

    How did you do?

    3e
    2 marks

    The population of penguins in the food web shown in part (a) decreases after a harsh winter.

    Explain the effect this might have on the shrimp and seal populations.

    How did you do?

    1a
    4 marks

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

    Food web for a desert community. Arrows point from the acacia plant to the scarab beetle and to the desert rat. Arrows point from the scarab beetle to the monitor lizard, from the desert rat to the monitor lizard, and from the desert rat to the fennec fox. An arrow points from the fennec fox to the monitor lizard. Arrows point from the monitor lizard to the hawk and from the fennec fox to the hawk.

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

    [1]

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

    [3]

    How did you do?

    1b
    1 mark

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

    Food web for a desert community. Arrows point from the acacia plant to the scarab beetle and to the desert rat. Arrows point from the scarab beetle to the monitor lizard, from the desert rat to the monitor lizard, and from the desert rat to the fennec fox. An arrow points from the fennec fox to the monitor lizard. Arrows point from the monitor lizard to the hawk and from the fennec fox to the hawk.

    Identify how many organisms in this food web are secondary consumers.

    • 2

    • 3

    • 4

    • 5

    Choose your answer

    1c
    4 marks

    The photograph shows a fennec fox.

    Photograph of a fennec fox standing on stony desert ground. It has very large, broad, upright ears, a small pointed face, pale sandy fur, a slender body and long thin legs, and a long bushy tail.

    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.

    How did you do?

    2a
    2 marks

    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.

    How did you do?

    2b
    1 mark

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

    How did you do?

    2c
    10 marks

    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.

    Year

    Number of mice per km2

    Number of owls in the entire woodland

    1

    2 × 103

    10

    2

    2 × 103

    12

    3

    3 × 103

    12

    4

    5 × 103

    16

    5

    1 × 103

    14

    (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]

    How did you do?

    3a
    1 mark

    A student studies the organisms in a pond community.

    Identify which of these is the correct description of a community.

    • The living organisms together with their non-living environment

    • The area where organisms live

    • The organisms of all species in a habitat

    • The organisms of one species in a habitat

    Choose your answer

    3b
    5 marks

    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.

    Trophic level

    Number of individuals per m2

    Total biomass in g per m2

    secondary consumers

    100

    1.0

    primary consumers

    1.5 x 104

    2.5

    producers

    7.2 x 1010

    17.5

    (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]

    A blank grid of small squares with heavier lines marking larger squares, provided for drawing a pyramid of biomass.

    How did you do?

    3c
    4 marks

    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]

    How did you do?

    1a
    1 mark

    The diagram shows a food web from a woodland ecosystem.

    Food web diagram for a woodland ecosystem, with arrows showing the direction of energy transfer. Oak tree has arrows to earthworm and to woodlouse. Earthworm has an arrow to shrew. Woodlouse has arrows to ground beetle, to centipede and to blackbird. Ground beetle has arrows to shrew and to blackbird. Centipede has an arrow to blackbird. Shrew and blackbird each have an arrow to sparrowhawk.

    Which organism in the food web is the producer?

    • Blackbird

    • Centipede

    • Earthworm

    • Oak tree

    Choose your answer

    1b
    1 mark

    Which organism acts as both a secondary consumer and a tertiary consumer?

    Use the food web in part (a).

    • Blackbird

    • Earthworm

    • Ground beetle

    • Sparrowhawk

    Choose your answer

    1c
    4 marks

    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.

    Level

    Energy in each level in kJ per m2 per year

    Producers

    8.7 × 105

    Primary consumers

    1.4 × 104

    Secondary consumers

    1.6 × 103

    (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]

    How did you do?

    1d
    6 marks

    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.

    Two black and white photographs of a woodlouse. On the left the woodlouse is uncurled and walking on stony ground, showing its overlapping segmented armour plates, its legs and its head. On the right a woodlouse of the same kind is curled tightly into a ball, so that only the hard outer plates are exposed and the legs and head are hidden inside.

    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]

    How did you do?

    2a
    1 mark

    The diagram shows a food chain in the Antarctic ocean.

    Food chain in the Antarctic ocean, labelled not to scale. An arrow points upwards from microscopic plants to krill, and a second arrow points upwards from krill to a whale.

    Identify which term describes the trophic level of the krill.

    • Predator

    • Prey

    • Primary consumer

    • Secondary consumer

    Choose your answer

    2b
    2 marks

    The diagram in part (a) shows a food chain in the Antarctic ocean.

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

    How did you do?

    2c
    2 marks

    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.

    How did you do?

    2d
    4 marks

    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.

    How did you do?

    2e
    4 marks

    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.

    How did you do?