(a) Name the disorder and any two symptoms caused by the gain of an extra copy of Chromosome 21.

Explain giving reasons why bee-keeping practices are carried out a large scale. Give the scientific name of the most commonly cultured species of honey bee.

How do ‘implants’ act as an effective means of contraception in human females? Mention one advantage of the implants over the pills.

The collection of certain moths after industrialisation in England (1920), showed population of light winged less than that of dark winged moths, which was reverse of the observation made prior to industrialisation (1850s). Explain the observation made, with reference to Darwinian natural selection.

List any four devices that develop in angiosperms to encourage cross pollination. Mention the advantage of such devices.