Does a female red eared slider need a male to have babies?

A female red-eared slider will lay eggs regardless of whether or not there is a male turtle around.

But unless a male turtle fertilizes these eggs, the eggs will not grow into baby turtles. They will be like the chicken eggs you buy from the supermarket -- which are also unfertilized and therefore unable to grow into baby chickens (chicks).

A similar thing happens with humans. A woman's ovaries (egg sacs) release one egg cell into her uterus (womb) every month. But unless the egg is fertilized by a man's sperm, it will simply flush itself out at the end of the month, along with the protective cushioning of blood and tissue that the uterus builds for it. If a sperm cell does fertilize the egg, then a fetus (unborn baby) will begin to form.