Some of the characteristics of living things are the ability to reproduce, active response and adaptation to the surrounding environment, cell composition and growth and development. Life forms have to exhibit all the characteristics to be considered a life form; spontaneous generation from chemical reactions is not an example of a life form.
Living things respond to their environment in various ways to survive and adapt. For example, if food is scarce, the organism might adjust its metabolism to use less energy and conserve for more abundant times. Some life forms, such as bears, go into hibernation during the winter to conserve their energy.
All life forms obtain and use energy to sustain life processes. The material for energy can be water and sunlight in the case of plants, or animals and plants in the case of animals. The energy is created through various biologial processes.
Reproduction is another characteristic of life forms. Two types of reproduction exist: sexual and asexual. Sexual reproduction occurs in more complex life forms; it involves a male and female of the species combining their genetic material, producing offspring that the female carries and births. Asexual reproduction involves a single life form creating a copy of itself, such as many single-celled organisms.