This was the less popular question this section. Many candidates defined parasites, saprophytes and symbionts/the organism rather than parasitism, saprophytism and symbiosis/the mode of life and so lost marks.
Most candidates performed poorly in describing the features of a named ecto parasite. Most candidates could however name the parasite e.g. tick, lice, flea but some candidates named tape worm which is an endo-parasite.
Expected answers include:
External Features
- Named ectoparasite (tick/lice/mite/flea)
- Dark; to hide in fur of host;
- Dorso-ventrally flattened to avoid falling off ;
- Biting/mouth parts; to attach to body of the host;
- Chitinous exoskeleton; to avoid drying up;
- Clawed digits for attachment
