According to the theory of evolution, every animal species came from an earlier animal species. This means that all animals are somehow connected in a kind of “animal family tree.” Scientists have found that different kinds of animals share many things in common: the way their bodies grow, how their brains work, how they need air to breathe, etc. But one group of animals has surprised scientists completely—the comb jelly. A comb jelly is a sea animal that looks like a jellyfish—it’s clear and can glow or produce light—but it doesn’t have the ability to sting other animals. Another thing comb jellies don’t have is certain genes that every other animal does. Genes are the building materials of a body. They decide what cells the body will make and what these cells will do. Animals have a set of genes that make brain cells. Comb jellies use a different set of genes which scientists don’t quite understand yet. Leonid Moroz is a scientist who has been studying comb jellies for many years. According to his research, comb jellies develop completely differently from other animals. It’s no surprise that he calls these fascinating creatures “aliens of the sea.” If comb jellies are on the same animal family tree as all the other animals, they must have started their own branch millions of years ago.

A. to share similar interests
B. to be responsible for and lead a business
C. how we spend time: at a job, at home, doing our hobbies
D. to do things that could harm you but will hopefully benefit you
E. a person’s understanding of who they are and where they come from