iGCSE Biology (0610)-20.4 Conservation - iGCSE Style Questions Paper 4

Question

Fig. 5.1 shows the changes in the percentage of the total global fish stocks that are overfished and those that are sustainable.

(a) Use the information in Fig. 5.1 to:
(i) State the percentage of fish stocks that were sustainable in 2020.
(ii) State which five-year period had the greatest increase in sustainable fish populations

(b) Overfishing is one reason why populations of fish decline.
Explain the risks to a species if its population size decreases.

(c) Describe and explain how fish stocks can be managed sustainably and how overfishing can be prevented through conservation.

▶️ Answer/Explanation

Solution

(a)(i) 66%

Explanation: From Fig. 5.1, the sustainable fish stocks in 2020 correspond to 66%, as the graph shows the remaining percentage after accounting for overfished stocks.

(a)(ii) 1985 to 1990

Explanation: The steepest upward trend in sustainable fish populations occurred between 1985 and 1990, indicating the greatest increase during this period.

(b) Reduction in genetic variation, inbreeding, increased recessive alleles, extinction risk, difficulty finding mates.

Explanation: A smaller population reduces genetic diversity, leading to inbreeding and higher chances of harmful recessive traits. It also increases extinction risk due to challenges in reproduction and adaptation.

(c) Education, monitoring, regulated net types/mesh sizes, reduced demand, fish farms, quotas, protected areas, closed seasons, restocking.

Explanation: Sustainable management includes enforcing fishing regulations (e.g., mesh size limits), creating marine protected areas, promoting aquaculture, and public awareness to reduce overharvesting and allow fish populations to recover.

Question

Fig. 6.1 shows a boreal toad, Anaxyrus boreas. This toad is listed as an endangered species.

(a) State the genus of the boreal toad.

(b) One reason for the boreal toad’s recent decrease in population is a disease caused by chytrid fungus. State two reasons other than disease that could cause the boreal toad to become endangered.

(c) Scientists investigated whether increasing the number of beneficial bacteria that live on the toads’ skin could provide protection against the fungus. The scientists took 42 toads and placed 21 in group 1 and 21 in group 2.

• Group 1 – the toads’ skin was treated with beneficial bacteria.
• Group 2 – the toads’ skin was not treated with beneficial bacteria.

The scientists measured the number of toads that became infected with the fungus.

Table 6.1 shows the results.

(i) Calculate the percentage of the 21 toads that have the fungal infection after 100 days in group 1 in Table 6.1. Give your answer to two significant figures. Space for working.

(ii) Using the information in Table 6.1, describe the effect of treating the toads with beneficial bacteria.

(d) There are conservation programmes to reintroduce boreal toads into their natural habitat.
(i) Describe why conservation programmes are set up for animals like the boreal toad.

(ii) Conservation programmes for other endangered animals, such as birds, use artificial insemination as part of a captive breeding programme. Describe how artificial insemination is carried out as part of a captive breeding programme.

▶️ Answer/Explanation

Solution

Ans

(a) Anaxyrus

Explanation: The genus is the first part of the binomial name Anaxyrus boreas.

(b) Any two from: climate change, habitat destruction, pollution, introduced species, overharvesting

Explanation: These factors can reduce populations by altering habitats or directly harming toads.

(c)(i) 62%

Calculation: \[ \text{Percentage infected} = \left( \frac{13}{21} \right) \times 100 = 61.9\% \approx 62\% \text{ (to 2 s.f.)} \]

(c)(ii) Bacterial treatment reduces fungal infections after 40 days. By day 100, only 62% of treated toads were infected vs. 100% of untreated toads.

Explanation: Beneficial bacteria compete with or inhibit the fungus, providing protection.

(d)(i) Conservation programs maintain biodiversity, prevent extinction, preserve ecosystems, and protect genetic diversity.

Explanation: These efforts ensure ecological balance and potential future benefits (e.g., medical research).

(d)(ii) Artificial insemination involves:

Collecting and screening sperm from males
Inducing ovulation in females
Inserting sperm into the reproductive tract
Maximizing genetic diversity by selecting donors

Explanation: This technique boosts breeding success in captive populations.

iGCSE Biology (0610)-20.4 Conservation – iGCSE Style Questions Paper 4

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