So here we have an example problem that asks, which of the following is an example of a parasitoid? And we've got these 4 potential answer options down below. Now of course, recall from our last lesson video that a parasitoid is an organism that lives as a parasite early on in its development during the larval stage. And often these parasitoids are fatal to their hosts. Now keeping that in mind, notice option a says, a tapeworm living inside a human's intestine, feeding on the food ingested by the human.
Now this is an example of an endoparasite, not an example of a parasitoid. And so for that reason, we can eliminate answer option a. It's an endoparasite because this parasite is living inside of the human's intestine. And although the tapeworm is negative to its host, negative to the human, it's not immediately fatal to the human. And the tapeworms can live inside the human's digestive systems for extended periods of time.
So again, it's not a parasitoid, and we can move on to option b. Now option b says a nematode, which is a type of roundworm, inside an ant causing the ant to display its reddened posterior area in the hope a bird eats it, which completes the complex life cycle of the nematode. Once again, here we have an endoparasite because the nematode is a parasite living inside of the organism, its host. But again, it's not a parasitoid as it's not living as a parasite only during its early developmental stage as a larva. Now moving on, option c says a tick that bites a dog and extracts its blood.
We know from our last lesson video that a tick is an example of an ectoparasite because it lives on the outside of its host, the dog. So again, we can eliminate option c. And, of course, this leaves answer option d, which says a wasp that lays its eggs on or in a caterpillar. And the larva that hatch from those eggs then eat the caterpillar when they hatch, again, killing the caterpillar. It's fatal to it.
This example here we covered in our last lesson video and it is the correct answer here for a parasitoid. So, we can indicate that d here is the correct answer. That concludes this example, and I'll see you all in our next video.