Which is a characteristic of the part of the atom marked "A"?
It contains most of the mass.
It is negatively charged.
It is mostly empty space.
It is composed of electrons.

Order can include highly organized structures such as cells, tissues, organs, and organ systems.

Interaction with the environment is shown by response to stimuli.

The ability to reproduce, grow and develop are defining features of life.

The concepts of biological regulation and maintenance of homeostasis are key to survival and define major properties of life.

Organisms use energy to maintain their metabolic processes.

Populations of organisms evolve to produce individuals that are adapted to their specific environment.

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the skeletons of most mammals reach a certain size and then stop growing. however, many animals, including some mammals, keep growing throughout their lives. kangaroos, for example, just keep growing and growing until they die. also, the longer an animal lives the greater the chance it might catch some deadly disease.