Earth Science: Types of Cohabitation – Parasitism
Parasites are organisms that withdraw nutrients from other species (hosts). This may damage the host but it will not, at least during the early stage, kill it. Parasites are mostly specialized for a specific host (host specificity).
Parasites are intricate organisms who have complex relationships to their hosts. Some parasites (phytoparasites) are parasitic on plants, while others (zooparasites) use animals as hosts.
There is a futher separation between ectoparasites (internal) and endoparasites (external) among animal parasites, as well as between full and partial plant parasites.
Animal ecto and endoparasites
Ectoparasites, which live outside the host’s body, frequently feed on the blood of the host, for instance, fleas, lice, or ticks. Some of these (such as the head louse in humans) are host specific, while ticks do not have a particular host specificity. These parasites often display special adaptations, for example, lice are not only wingless, but they also have a flattened body and special oral tools adapted to their mode of feeding.
Temporary parasites, such as mosquitoes, carry out non-permanent attacks. Animal endoparasites, on the other hand, include all parasites that live inside a host. They are found most commonly in the digestive tract and in the blood; however, they can also occur in muscle tissue. Endoparasites show even greater adaptations to their particular mode of life. For instance tapeworms do not have a digestive tract and absorb the food digested by the host directly along their body surface.
Partial and full plant parasites
Among plant parasites, partial parasites (hemiparasites) differ from full parasites (holoparasites). The latter no longer use photo-synthesis because they remove all of their required nutrients from a host plant. An example is the toothwort (Lathraea), which forms a long, heavily branched subterranean root system to which numerous suction organs (haustoria) are attached.
They are used by the parasite to tap into the roots of other plants, specifically trees like alders and beeches. Partial para- sites, however, still photosynthesize, but they remove water and nutrient salts from their host plants. A typical semiparasite is the evergreen mistletoe, which lives on trees and is normally not a threat to its host.
NEST (BROOD) PARASITISM
In nest parasitism, animals take advantage of the brood behavior of another species, whereby the progeny of the host species is adversely affected in favor of their own progeny. This form of parasitism is found among birds and insects. For instance larvae of the ichneumon wasp parasitize the bodies of certain caterpillars.
However, the most well-known example is that of the cuckoo, which lays its eggs in the nests of other birds. These birds then raise the cuckoo’s chicks as one of their own. After hatching, the young cuckoo usually throws the eggs or the chicks of the host parents out of the nest.
BASICS
SAPROPHYTES are organisms that obtain their nutrients from dead and decaying organic plant or animal matter.
Typical saprophytes include many fungi and bacteria, and, among plants, the rare ghost plant (or indian pipe).