<P> Parasites are divided into two groups: 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 . Due to the different strategies of endoparasites and ectoparasites, they require different adaptations to derive nutrients from their host . </P> <P> 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 . 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 . </P> <P> Endoparasites live inside the body of the host . This group includes helminths, trematodes and cestodes . Endoparasites are two groups of parasites: intercellular and intracellular parasites . Intercellular parasites live in spaces within the host e.g. the alimentary canal, whereas intracellular parasites live in cells within the host e.g. erythrocytes . Intracellular parasites typically rely on a third organism, a vector, to transmit the parasite between hosts . Rather than requiring adaptations to penetrate the host, as ectoparasites do, endoparasites are in a nutrient - rich location so they instead have adaptations to maximise nutrient absorption . Endoparasites have a readily available and renewable supply of nutrients inside the host, which in some cases is pre-digested by the host, so mechanisms of nutrient absorption across their body surface is a common feature . As part of their life cycle strategy, endoparasites must also be able to transmit from within the host body and survive the hostile environment within the host . Only by achieving this can they benefit from acquiring nutrition in this way . </P> <P> Endoparasites have various anatomical and biochemical adaptations, typically at the host - parasite interface, to maximise nutrient acquisition . One such adaptation is the tegument, a metabolically active external cover that plays an important role in nutrient extraction from the host . The parasite tegument is permeable to various organic solutes and has transporters for the facilitated or active uptake of nutrients . Various studies have attempted to characterise these transporters in a number of parasites e.g. the amino acid transporter molecules in protozoa . Cestodes do not have a gut so the tegument is therefore critical for nutrient uptake . In cestodes the tegument is highly efficient with spine - like microtriches, similar to microvilli, to increase the surface area available for nutrient acquisition . In many parasites the tegument structure has folds or microvilli to maximise the surface area available for diffusion and uptake of nutrients . The tegument also commonly has additional organelles and features with important functions in metabolism including the glycocalyx . The glycocalyx is a carbohydrate - rich layer that enhances nutrient absorption and secretes enzymes to aid primary digestion . </P>

Who derives nutrition from plants as a parasite