Chapter 2

Introduction to Living Organisms

2.1 Lesson 2.1: What are Living Things?

Lesson Objectives

• List the defining characteristics of living things.


• List the needs of all living things.

Check Your Understanding

• How do life scientists study the natural world?


• Are scientific theories just a ”hunch” or a hypothesis?

Introduction

How would you define a living thing? In other words, what do mushrooms, daisies, cats,
and bacteria have in common? (The series of pictures in theFigure2.1 are additional
representations.) All of these are living things, ororganisms. It might seem hard to think
of similarities among such diverse organisms, but there are actually many similarities. The
chemical processes inside all organisms are the same. For example, all living things encode
their genetic information in the same way. And many organisms share the same needs, such
as the need for energy and materials to build their bodies. Living things have so many
similarities because all living things have evolved from the same common ancestor that lived
billions of years ago.

All living organisms: