Question

While living in and on the host species, the animal parasite has evolved certain adaptations. Describe these adaptations with examples.

Answer 1

Definition of parasitism

Parasitism is a relationship between organisms of different species where one organism (parasite) obtains its nutrition directly from the other organism (host) affect the host. In this interaction, one species is benefitted while the other is harmed.

Many parasites have evolved to be host-specific (they can parasitise only a specific species of host) in such a way that both host and the parasite tend to co-evolve.

Types of parasitism

There are two main types of parasites:-

● Endoparasites: These parasites live inside the host tissues or cells, deriving nutrition from the host. Examples include tapeworms that live inside the gut of the host, Plasmodium that lives and multiplies within liver cells and red blood cells of the host etc.

● Ectoparasites: These parasites derive nutrition by residing on the body surface of the host and not inside it. For example, ticks, fleas, Cuscuta etc.

Adaptations in endoparasites

Since endoparasites live inside the host they have the following adaptations:-

● Loss of sense organs: Sense organs are required for free living forms. Since parasites like tapeworms live inside the body, the sense organs are lost.

● Presence of adhesive organs: These organs are required for the parasite to get attached firmly to the tissues to derive nutrition from the host. For example, the presence of hooks and suckers in tapeworms and liver flukes.

● Presence of thick cuticle: The body of the endoparasite has a thick resistant cuticle to prevent the host’s digestive juices from destroying it.

● Loss of digestive system: Since parasites receive digested food from the host, they do not require a digestive system. For example, tapeworms lack a digestive system.

● High reproductive capacity: Parasites have a highly efficient reproductive system so that they can produce many progenies to ensure survival and propagation. Example Ascaris lumbricoides produces 2 lacs eggs/day.

Adaptations in ectoparasites

The following adaptations are present in ectoparasites:-

● Presence of haustoria: Parasitic plants like Cuscuta have parasitic roots called haustoria that invade the conducting tissue of the host plant to derive nutrition.

● Presence of specialised mouthparts: Ticks and lice have feeding parts that can penetrate the epidermis of the host to feed on the blood.