Home / A level Biology 18.2 Biodiversity – Exam style question – Paper 4

A level Biology 18.2 Biodiversity – Exam style question – Paper 4

A level Biology Paper 4 - All Chapters
Question

The Asian common toad, Duttaphrynus melanostictus, arrived accidentally in eastern Madagascar in 2010 on a ship.

Fig. 9.1 shows an Asian common toad.

Asian common toad

The Asian common toad is now regarded as an invasive alien species because:

  • it breeds fast in the warm, wet conditions of eastern Madagascar
  • it can travel up to 2.5km per year
  • its skin contains poison, which is highly toxic to humans and predators.

Suggest ways in which the Asian common toad may affect the ecosystem of eastern Madagascar.

(b) Zoos work with local groups around the world to help conserve endangered species. One example of this is the use of assisted reproduction, such as IVF, with endangered mammals such as the eastern black rhino. Outline the process of IVF.

▶️ Answer/Explanation
Solution

(a) Any four from:

  1. Not predated (due to toxicity), leading to uncontrolled population growth.
  2. Preys on native species, reducing their numbers.
  3. Disrupts food webs by altering predator-prey dynamics.
  4. Rapid spread due to high mobility (2.5 km/year).
  5. Reduces biodiversity by outcompeting native species.
  6. May cause extinction of vulnerable native species.
  7. Competes for resources (food, water, breeding sites).
  8. Introduces new diseases to native fauna.

Explanation: The toad’s toxicity, rapid reproduction, and mobility allow it to dominate ecosystems, displacing native species and destabilizing ecological balance.

(b) Outline of IVF process (any four steps):

  1. Hormonal stimulation: Females are given FSH to induce superovulation (multiple egg maturation).
  2. Egg collection: Ova/oocytes are harvested surgically or via ultrasound-guided aspiration.
  3. Fertilization: Sperm (often from genetically diverse males) is introduced to eggs in vitro.
  4. Embryo screening: Healthy embryos are selected for implantation.
  5. Implantation: Embryos are transferred to the uterus of a surrogate or the same female.
  6. Cryopreservation: Excess embryos may be frozen for future use.

Explanation: IVF helps conserve endangered species by maximizing genetic diversity and reproductive success, especially in small populations like the eastern black rhino.

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