CAIE IGCSE Biology 19.2 Food Chains and Food Webs Questions

Practise food-chain and food-web questions by naming trophic roles, interpreting pyramids and explaining energy losses between trophic levels.

Exam points

construct and interpret food chains with arrows from food to feeder, beginning with a producer
construct food webs, trace connected prey and predators, and predict linked population changes
identify producer, consumer and decomposer roles from feeding and organic-material evidence
label primary to quaternary consumers and trophic levels from feeding links and pyramids
recognise organisms feeding at multiple trophic levels and count named levels or consumers
draw and interpret pyramids of numbers or biomass, including bars, labels and missing values
explain when biomass represents a food chain better than numbers for large and small organisms
interpret energy pyramids and identify the greatest-energy trophic level at the base
calculate energy transferred, lost or the percentage transfer between adjacent trophic levels
explain energy losses through respiration, heat, movement or waste and why higher levels support less
compare energy pyramids with number or biomass pyramids using time and organism-size evidence
explain why eating crops directly is more efficient than eating crop-fed livestock

Covered syllabus points

19.2.1—Food chain as showing the transfer 19.2.2—Construct and interpret simple food 19.2.3—Food web as a network 19.2.4—Producer as an organism that makes its 19.2.5—Consumer as an organism that gets its 19.2.6—Consumers may be classed as primary 19.2.7—Herbivore as an animal that gets its 19.2.8—Carnivore as an animal that gets its 19.2.9—Decomposer as an organism that gets 19.2.10—Food chains and food webs to describe 19.2.11—Pyramids of numbers and pyramids 19.2.12—Pyramids of biomass 19.2.13—Trophic level as the position 19.2.14—Following as the trophic levels 19.2.15—Pyramids of energy 19.2.16—Pyramids of energy 19.2.17—Transfer of energy from one trophic 19.2.18—Explain, in terms of energy loss, why 19.2.19—It is more energy efficient for humans

[Maximum number: 1]

The diagram shows a food web.

Figure for Question 1 — CAIE IGCSE Biology

What do the arrows represent?

the absorption of oxygen

the absorption of water

the flow of energy

the release of carbon dioxide

[Maximum number: 7]

Coral reefs are important ecosystems.

(a)

Fig. 6.2 is part of a food web for a coral reef ecosystem which is similar to the one shown in Fig. 6.1.

Fig. 6.2

[ 7 ]

(i)

State the number of secondary consumers shown in Fig. 6.2.

[ 1 ]

(ii)

State the name of a species that feeds at more than one trophic level in Fig. 6.2.

[ 1 ]

(iii)

State the number of different organisms in the shortest food chain in Fig. 6.2.

[ 1 ]

(iv)

State the evidence from the food web in Fig. 6.2, that phytoplankton are producers.

[ 1 ]

(v)

It is rare for there to be more than five trophic levels in an ecosystem.

Explain what limits the number of trophic levels in food webs.

[ 3 ]

[Maximum number: 18]

(a)

A student recorded the information about an aquatic habitat.

Fig. 4.1 shows the student's notes.

Fig. 4.1

[ 13 ]

(i)

Construct a food web to show the feeding relationships described in Fig. 4.1.

Do not draw the organisms.

[ 4 ]

(ii)

Complete Table 4.1 using the information in Fig. 4.1 by identifying the names of the missing trophic levels and one organism at each different trophic level.

Table 4.1

[ 3 ]

(iii)

Outline how the energy in the primary consumers in this aquatic food web is used to produce biomass in the secondary consumers.

[ 3 ]

(iv)

Humans also eat salmon.

Predict the impact on the feeding relationships shown in Fig. 4.1 of overharvesting of salmon.

[ 3 ]

(b)

Describe what is meant by the term decomposer.

[ 1 ]

(c)

Animals such as salmon can be farmed for meat.

Explain why it is more energy efficient for humans to eat crop plants than to eat livestock that have been fed on crop plants.

[ 4 ]

[Maximum number: 1]

Coral reefs are important ecosystems.

Fig. 6.2 is part of a food web for a coral reef ecosystem which is similar to the one shown in Fig. 6.1.

Fig. 6.2

State the number of different organisms in the shortest food chain in Fig. 6.2.

[Maximum number: 4]

A student recorded the information about an aquatic habitat.

Fig. 4.1 shows the student's notes.

Fig. 4.1

Construct a food web to show the feeding relationships described in Fig. 4.1.

Do not draw the organisms.

[Maximum number: 1]

Coral reefs are important ecosystems.

Fig. 6.2 is part of a food web for a coral reef ecosystem which is similar to the one shown in Fig. 6.1.

Fig. 6.2

State the evidence from the food web in Fig. 6.2, that phytoplankton are producers.

[Maximum number: 1]

Fig. 6.1 shows part of the carbon cycle in the ocean.

Fig. 6.1 (not to scale)

Suggest the role of zooplankton in this ecosystem.

[Maximum number: 1]

The diagram shows the feeding relationships in a food web.

Figure for Question 8 — CAIE IGCSE Biology

Which organism may feed as both a secondary and a tertiary consumer?

fox

owl

blackbird

rabbit

[Maximum number: 1]

Describe what is meant by the term decomposer.

[Maximum number: 3]

A student recorded the information about an aquatic habitat.

Fig. 4.1 shows the student's notes.

Fig. 4.1

Humans also eat salmon.

Predict the impact on the feeding relationships shown in Fig. 4.1 of overharvesting of salmon.

[Maximum number: 3]

(a)

A scientist studied communities in different parts of a desert and estimated the biomass of the organisms in each area.

He divided the organisms into four groups according to their roles in the food web as shown in Table 2.1.

Detritivores are animals that eat dead organisms or parts of organisms.

Table 2.1

Some of these results are shown as a pyramid of biomass in Fig. 2.2.

Fig. 2.2

[ 3 ]

(i)

Use the information in Table 2.1 to complete the pyramid of biomass in Fig. 2.2.

[ 2 ]

(ii)

The scientist observed the detritivores and decided to include them with herbivores in this pyramid of biomass.

Suggest what the scientist discovered about the detritivores that made him make this decision.

[ 1 ]

[Maximum number: 3]

Table 2.1

Some of these results are shown as a pyramid of biomass in Fig. 2.2.

Fig. 2.2

Explain the advantages of presenting information about food webs as a pyramid of biomass and not as a pyramid of numbers.

[Maximum number: 1]

The diagram shows a pyramid of numbers.

Figure for Question 13 — CAIE IGCSE Biology

What is the correct description of the trophic levels?

producers

primary consumers

secondary consumers

producers

secondary consumers

tertiary consumers

secondary consumers

primary consumers

producers

secondary consumers

tertiary consumers

producers

[Maximum number: 1]

Fig. 6.2 shows the pyramid of energy for a food chain in an ocean ecosystem.

Fig. 6.2

On Fig. 6.2, label the trophic level containing herbivores.

[Maximum number: 1]

Which statement about a pyramid of energy for a food chain is correct?

It shows how energy is lost at each trophic level.

It shows the energy stored at each trophic level.

It shows the input of energy from the principal source.

It shows the total energy stored within an ecosystem.

[Maximum number: 2]

Fig. 6.2 shows the pyramid of energy for a food chain in an ocean ecosystem.

Fig. 6.2

State two advantages of using a pyramid of energy rather than a pyramid of biomass to represent a food chain.

1

2

[Maximum number: 3]

A student recorded the information about an aquatic habitat.

Fig. 4.1 shows the student's notes.

Fig. 4.1

Outline how the energy in the primary consumers in this aquatic food web is used to produce biomass in the secondary consumers.

[Maximum number: 3]

Fig. 6.2 shows the pyramid of energy for a food chain in an ocean ecosystem.

Fig. 6.2

Explain why pyramids of energy usually have fewer than five trophic levels.

[Maximum number: 4]

Animals such as salmon can be farmed for meat.

Explain why it is more energy efficient for humans to eat crop plants than to eat livestock that have been fed on crop plants.

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Covered syllabus points

Question 1

Question 2

Question (a)

Question (i)

Question (ii)

Question (iii)

Question (iv)

Question (v)

Question 3

Question (a)

Question (i)

Question (ii)

Question (iii)

Question (iv)

Question (b)

Question (c)

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9

Question 10

Question 11

Question (a)

Question (i)

Question (ii)

Question 12

Question 13

Question 14

Question 15

Question 16

Question 17

Question 18

Question 19