Which of the following organisms is an endo-parasite?

Step 1: Analyze the question We need to find the organism that is an endo-parasite, meaning a parasite that lives inside the body of its host.

Step 2: Explain the concept

• Endo-parasite: lives inside the host's body (in the gut, blood, liver, and so on). Endo- means "inside."
• Ecto-parasite: lives on the outside surface of the host (skin, fur, feathers). Ecto- means "outside."

Step 3: Examine each option

• A. Tapeworm: lives in the intestine of humans, pigs and cattle, attached to the gut wall by hooks and suckers. It absorbs digested food directly. This is an endo-parasite.
• B. Flea: lives on the skin or fur of mammals and birds and sucks blood. This is an ecto-parasite.
• C. Tick: attaches to the skin of animals such as cattle and dogs to suck blood. This is an ecto-parasite.
• D. Aphid: lives on the outside of plants (stems and leaves) and sucks sap. This is an ecto-parasite.

Step 4: Answer The tapeworm is the only one that lives inside its host, so the answer is A.

Exam tip: Remember "Endo = Enter". Endo-parasites include tapeworm, roundworm, liver fluke, hookworm and Plasmodium. Ecto-parasites include flea, tick, louse, bedbug and aphid. If a parasite sits on the surface, it is ecto. If it is in the gut or blood, it is endo.