The basic unit of structure and function in living things.
A group of similar cells that perform a specific function.
A structure that is composed of different kinds of tissue.
A characteristic that helps an organism survive or reproduce in its environment.
The process by which a new organism develops from the joining of two sex cells.
The joining of an egg cell and a sperm cell.
The process by which a single organism produces a new organism identical to itself.
One of about 35 major groups into which biologists classify members of the animal kingdom.
an animal with a backbone
an animal without a backbone