Question

Animals of which phylum have hooks and suckers and are endoparasite on other animals?
A. Platyhelminthes
B. Annelida
C. Aschelminthes
D. Arthropoda

Answer 1

Hint: Structures found in parasitic species are hooks and suckers. Hooks help the body get hooked to the host's organs and the suckers help it to absorb nutrients from the host tissues. A parasite which lives in its host's internal organs or tissues is an endoparasite.

Complete answer: 

> Platyhelminthes consists of organisms that have a dorsiventral flattened body and bear hooks and suckers. Their bodies are coated with a dense tegument, shielding them from the action of the host's digestive juices. The tegument also helps to absorb nutrients from the body of the host. A flat body is the most distinctive characteristic of these invertebrates. Since there are no cavities in the body, they are smooth. The body is also not segmented and there are no advanced structures available for them. Around eighty per cent of the flatworms in nature are parasitic, though there are also a few free-form flatworms. Scavengers or predators are the free-living forms. On the tissues of the host organism in which they live, the parasitic species feed.
a) Annelida: They have a body which is long and segmented. Annelids are symmetrical bilaterally.
Triploblastic, they are. They also exhibit organ system grade of organisation, demonstrating distinction of organs. It protects the body with a thin cuticle. They are coelomates. There is a corporeal cavity or coelom. In wet habitats, moist soil, freshwater and seawater, is where annelids are found. Used for locomotion, they have parapodia and chitinous setae. Because of the presence of haemoglobin, the body looks bright.
b) Aschelminthes: Aschelminthes can be parasitic or free-living. In soils and sediments, free-living species are highly common and they feed on bacteria. While some others are pests of plants and may cause disease in economically valuable crops. The rests are parasites in animals and human beings that can be found. Hookworms, pinworms, Guinea worms, and intestinal roundworms are some of the parasitic worms.
c) Arthropoda: They have a body which is long and segmented. Annelids are symmetrical bilaterally. They also exhibit organ system grade of organisation, demonstrating distinction of organs. It protects the body with a thin cuticle. They are coelomates. There is a corporeal cavity or coelom. In wet habitats, moist soil, freshwater and seawater, the Annelids live. Used for locomotion, they have parapodia and chitinous setae. Because of the presence of haemoglobin, the body looks bright. 

Hence, the correct answer is option A.

Note: Platyhelminthes are a group of spineless creatures and are often referred to as flatworms. So, they seem like animal-like strips. They are usually simple invertebrates, bilateral, unsegmented and delicate bodied.