Question

comment on the mechanism called digestion in different organism

Answer 1

The food passes through a continuous canal called alimentary canal. The canal can be divided into various compartments: (1) the buccal cavity, (2) foodpipe or oesophagus, (3) stomach, (4) small intestine, (5) large intestine ending in the rectum and (6) the anus.The activities of the gastro-intestinal tract [alimentary canal] are under neural and hormonal control for proper coordination of different parts.The sight, smell and/or the presence of food in the oral cavity can stimulate the secretion of saliva.Gastric and intestinal secretions are also, similarly, stimulated by neural signals.The muscular activities of different parts of the alimentary canal can also be moderated by neural mechanisms.

Parasitic nutrition is a mode of heterotrophic nutrition where an organism (known as a parasite) lives on the body surface or inside the body of another type of organism (known as a [Host (biology)]|[host]). The parasite obtains nutrition directly from the body of the host. Since these parasites derive their nourishment from their host, this symbiotic interaction is often described as harmful to the host. Parasites are dependent on their host for survival, since the host provides nutrition and protection. As a result of this dependence, parasites have considerable modifications to optimise parasitic nutrition and therefore their survival.

Parasites are divided into two groups: [List of parasitic organisms|endoparasites]] and ectoparasites. Endoparasites are parasites that live inside the body of the host, whereas ectoparasites are parasites that live on the outer surface of the host and generally attach themselves during feeding.[1] Due to the different strategies of endoparasites and ectoparasites they require different adaptations in order to acquire nutrients from their host.

Parasites require nutrients to carry out essential functions including reproduction and growth. Essentially, the nutrients required from the host are carbohydrates, amino acids and lipids. Carbohydrates are utilised to generate energy, whilst amino acids and fatty acids are involved in the synthesis of macromolecules and the production of eggs.[2] Most parasites are heterotrophs, so they therefore are unable to synthesise their own 'food' i.e. organic compounds and must acquire these from their host.