Which of the following is a parasitic worm? a. leeches b. hookworms c. planaria d. flukes

A parasitic organism is one that benefits from its host, but doesn't benefit the host, in fact, it has negative effects to the host.

In this case, we have 4 examples of worms, and we're supposed to find the parasitic one. And, I think this is something we can do without having to go deep into the subject, because at first sight, we can distinguish a worm, that we all know isn't paricularly good - leeches.

→ Leeches are an example of parasitic annelides that live in high-humidity environments, and live partly from the blood they suck from animals and sometimes humans.

Hope it helped,

BioTeacher101

not necessarily. higher fitness requires the organism to be reproductive successful. for example, an organism at age 10 with 15 offspring is much more fit than an organism at age 15 with only 5 offspring.