Biology  5/e   Raven/Johnson
	Student   Online Learning Center

Theories: To a scientist, a theory is an explanation or hypothesis that has been tested many times and has a lot of scientific evidence to support it. Knowledge of chemistry has contributed greatly to the theory of how life first evolved on this planet.

The scientific method: When scientists do science, they follow a logical sequence of steps which includes asking questions, making observations, formulating hypotheses, and conducting further experiments to test hypotheses.

Characteristics of life: All living organisms share the four same characteristics no matter how different the organisms appear to be. All living organisms – from bacteria to amoeba to mushrooms to oak trees to goats – are made up of one or more cells which are made up of molecules and atoms; all respond to both external and internal stimuli; all grow, develop and reproduce; and all have a wide variety of regulatory mechanisms that help keep them functioning and alive.

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