Final answer:
Biology is the science that studies life and defines its characteristics. All living things share key components that determine if they are considered alive. These characteristics include order, sensitivity, reproduction, growth and development, regulation, energy processing, and evolution.
Step-by-step explanation:
Biology is the science that studies life. All living organisms share several key characteristics such as order, sensitivity or response to stimuli, reproduction, growth and development, regulation/homeostasis, energy processing, and evolution. When viewed together, these eight characteristics serve to define life. Living things are highly organized parts of a hierarchy that includes atoms, molecules, organelles, cells, tissues, organs, and organ systems. In turn, biologists group organisms as populations, communities, ecosystems, and the biosphere. The great diversity of life today evolved from less-diverse ancestral organisms over billions of years. We can use a phylogenetic tree to show evolutionary relationships among organisms.