Final answer:
Most scientists agree that to classify something as living, it must demonstrate seven characteristics, including responding to the environment, growth, reproduction, homeostasis, complex chemistry, cellular structure, and energy use. Nonliving examples that may exhibit some of these traits include flames and crystals, but they do not meet all required criteria to be classified as living.
Step-by-step explanation:
Characteristics of Living Things
To classify a substance as a living thing, most scientists agree that an object must exhibit seven characteristics. These characteristics are necessary to consider an organism 'alive.' They include:
- Response to the environment
- Growth and development
- Reproduction
- Maintenance of homeostasis
- Complex chemistry
- Cellular structure
- Energy usage
For example, a nonliving object like a flame responds to the environment and uses energy but does not meet all the other criteria such as growth, development, and reproduction. Similarly, a crystal may grow but lacks complex chemistry and cellular structure that are essential for life.
Classifying Substances Using Models
Another aspect of classification comes from chemistry, where substances can be classified as elements, compounds, or mixtures. One can use models, like colored balls, to represent these substances and classify them accordingly. However, this chemical classification does not directly relate to whether a substance is considered living or nonliving.