The Asian common toad, Duttaphrynus melanostictus, arrived accidentally in eastern Madagascar in 2010 on a ship. [Figure 9.1] shows an 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.

Mark scheme

Marking points from the official mark scheme (May/June 2024). The mark or mark type is shown in brackets.

1. [4] (a) any four from:
2. [4] (a) 1 not predated / predators killed (as toxic) ;
3. [4] (a) 2 eats / decreases numbers, of, native / local, species ;
4. [4] (a) 3 disrupts, food web / food chain / ecosystem ;
5. [4] (a) 4 can spread to other areas / numbers increase rapidly ;
6. [4] (a) 5 reduces biodiversity ;
7. [4] (a) 6 can cause extinction (in, native / local, species) ;
8. [4] (a) 7 competes (with native species) for, space / breeding areas / food / water / resources ;
9. [4] (a) 8 introduces / new, disease ;
10. [4] (b) A eggs for ova/oocytes
11. [4] (b) any four from:
12. [4] (b) 1 (females) given, hormones / FSH, to stimulate maturation of, ova / oocytes or (females) given, hormones / FSH, to stimulate superovulation ;
13. [4] (b) 2 ova/oocyte, collection / harvesting ;
14. [4] (b) 3 sperm added to, ova / oocytes or ref. to fertilisation ;
15. [4] (b) 4 sperm from genetically distant male / AW ;
16. [4] (b) 5 embryos, checked / selected ;
17. [4] (b) 6 embryo placed into uterus ;
18. [4] (b) 7 some embryos can be frozen ;