Life science or biology is the study of living things.  Life can be characterized by a group of properties common to all living organisms.  First, living things are made of basic units called cells which are the structural and functional units of life.  Secondly, they are based on a universal genetic code. Thirdly, all living things obtain and use energy to grow, develop, and reproduce.  Finally, living things respond to their environment, maintain stability, and change over time. The study of one living thing always involves the study of other living things.  Human existence depends on the existence of all living things on Earth.

Biological sciences are all tied together by big ideas or themes.  Examples of these themes are explained in the chart below.

Life can be studied at the following levels.

• The biosphere is the part of the Earth that contains all ecosystems.
• An ecosystem is made up of communities and their nonliving environment.
• A community is a population that lives in a defined area.
• An organism is an individual living thing.
• Groups of cells are tissues, organs, and organ systems.
• Cells are the smallest functional unit of life.
• Molecules are groups of atoms that are the smallest unit of compounds.

Review:

1. Life science is the study of what?
2. Describe three characteristics of living things.
3. What is the biosphere?