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CIE iGCSE Co-Ordinated Science B18.1 Energy flow Exam Style Questions Paper 3

CIE iGCSE Co-Ordinated Science Paper 3 - All Chapters

Question

Fig. 4.1 shows part of a food web on a remote island.
(a) State the principal source of energy input to the food web in Fig. 4.1.
(b) Identify the two organisms in Fig. 4.1 that the lapwing bird eats.
(c) Identify all the producers in the food web in Fig. 4.1.
(d) Hedgehogs are introduced to the island by humans.
Use Fig. 4.1 to describe how hedgehogs affect the population of lapwing birds.
(e) When organisms in the food web die, other organisms like earthworms get their energy from the dead organic material.
State the type of organism that gets its energy from dead organic material.
(f) Hedgehogs hunt at night when it is dark.
Complete the sentences about how hedgehogs detect their prey.
Choose words from the list.
ciliated       chemicals       light       motor       receptor       sound
Hedgehogs use their sense of smell to detect …………………… in the air.
Their nose contains groups of …………………… cells which detect the smell.

Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):

• Topic B18.1 — Energy flow (Part (a))
• Topic B18.2 — Food chains and food webs (Part (b), (c), (d), (e))
• Topic B13.1 — Coordination and response (Part (f))

▶️ Answer/Explanation

(a) Sun
The Sun is the principal source of energy input to all food webs. Plants capture light energy from the Sun and convert it into chemical energy through photosynthesis.

(b) caterpillar and leaf beetle
The lapwing bird eats both caterpillars and leaf beetles, as shown by the arrows pointing from these organisms to the lapwing bird in the food web.

(c) Primrose plants and buttercup plants
Producers are organisms that make their own food by photosynthesis. In this food web, the primrose plants and buttercup plants are the producers at the base of the food web.

(d) Hedgehogs cause the population of lapwing birds to decrease.
Hedgehogs directly eat lapwing birds, reducing their numbers. Additionally, hedgehogs eat caterpillars, which are also a food source for lapwing birds. This increases competition for food, further reducing the lapwing population.

(e) Decomposer
Decomposers such as earthworms, bacteria and fungi obtain their energy from dead or waste organic material, breaking it down and releasing nutrients back into the ecosystem.

(f) Hedgehogs use their sense of smell to detect chemicals in the air.
Their nose contains groups of receptor cells which detect the smell.
Receptor cells are specialised cells that detect specific stimuli such as chemicals (for smell), light, or sound. In the nose, chemoreceptors detect chemical molecules in the air.

Question

Fig. 4.1 is a picture of a rhino.
(a) Rhinos only eat plants.
Tick (✓) two boxes that describe rhinos.
☐ carnivore
☐ decomposer
☐ herbivore
☐ primary consumer
☐ producer
☐ secondary consumer
(b) There are different species of rhino.
Describe what is meant by the term species.
(c) Some of the rhino species are endangered.
One reason the rhinos are endangered is because their habitat has been destroyed.
(i) Suggest two other reasons why rhinos are endangered.
(ii) Describe one reason why habitats are destroyed.
(d) Scientists are working to conserve all the rhino species.
They use different conservation methods for different species of rhino.
The method they use depends on how many rhinos are still alive in the wild.
Fig. 4.2 is a graph showing the population of each rhino species in 2023.
(i) Identify the rhino species in Fig. 4.2 with the highest population.
(ii) Use Fig. 4.2 to calculate how many times bigger the population of white rhino is compared to the population of black rhino.
(iii) Black rhinos and white rhinos are kept in protected reserves where they can be monitored 24 hours a day.
Suggest one different conservation method that can be used for the Sumatran and Javan rhinos.

Topic codes:

• Topic B18.1 — Energy flow (Part (a))
• Topic B18.2 — Food chains and food webs (Part (a))
• Topic B19.1 — Habitat destruction (Part (c)(ii))
• Topic B19.2 — Conservation (Part (b), (c)(i), (d)(i), (d)(ii) & (d)(iii))

▶️ Answer/Explanation

(a) Herbivore and primary consumer
Rhinos eat only plants, making them herbivores. In a food chain, herbivores that feed directly on producers (plants) are primary consumers. Producers make their own food through photosynthesis, while carnivores and secondary consumers eat other animals.

(b) A species is a group of organisms that can reproduce to produce fertile offspring.
Organisms belong to the same species if they can interbreed and produce viable offspring that can also reproduce. Individuals of different species cannot produce fertile offspring due to reproductive barriers.

(c)(i) Two other reasons why rhinos are endangered:

  • Hunting/poaching – Rhinos are killed for their horns, which are valued in some cultures for traditional medicine or as status symbols.
  • Climate change – Changes in temperature and rainfall patterns can affect the availability of food and water sources for rhinos.
  • Pollution – Contamination of water sources and habitats with chemicals can harm rhino health and reduce their food supply.
  • Competition from introduced species – Non-native species may compete with rhinos for food and water resources.

(c)(ii) Habitats are destroyed due to:
Land being cleared for housing, industry, crop plant production, livestock production, or extraction of natural resources such as mining and logging. Pollution can also contaminate and destroy habitats.

(d)(i) White rhino
From Fig. 4.2, the white rhino population is approximately 16,000, which is the highest among all rhino species.

(d)(ii) White rhino population = 16,000; Black rhino population = 6,000
\(\frac{16,000}{6,000} = 2.7\)
The white rhino population is 2.7 times bigger than the black rhino population.

(d)(iii) Captive breeding programmes
For critically endangered species like Sumatran and Javan rhinos with very small populations, captive breeding programmes can be used. These involve breeding rhinos in controlled environments to increase their numbers before releasing them back into protected areas. Education programmes can also help raise awareness and reduce demand for rhino products.

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