When an organism is sessile, or slow moving it might be very hard for that organism to find food, shelter and a reproductive mate.
One of many solutions to the problem of finding a mate is hermaphroditism.
When an organism is hermaphroditic it means that it has the reproductive organs of both sexes and that it is able to self-fertilize.
This solution, although sometimes very useful, if used all the time can lead to inbreeding and have negative effects on the genetic diversity of the population. Therefore, hermaphroditic organisms self-fertilize only in cases where there is no available mate to be found.
That population will eventually face extinction due to the lack of organisms that has the ability to survive
Also, intersexual selection, or mate choice, occurs when females choose between male mates. Traits selected by male combat are called secondary sexual characteristics (including horns, antlers, etc.), which Darwin described as "weapons", while traits selected by mate (usually female) choice are called "ornaments".
Euglena is a large genus of unicellular protists: they have both plant and animal characteristics. All live in water, and move by means of a flagellum. This is an animal characteristic. Most have chloroplasts, which are characteristic of algae and plants