Themes of Life

Themes in the Study of Life

Campbell Biology 9th ed. Chapter 1

What is Biology?
• Biology is the scientific study of life
• Biologists ask questions such as
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–
–

How do multicelled organisms develop?
How does the human mind work?
How do living things interact in communities?

• Life defies a simple, one-sentence definition • Life is recognized by what living things do

Some Properties of Life
• Order
• Evolutionary adaptation • Response to environment • Reproduction
• Growth and development • Energy processing
• Regulation

Biologists Study Life at
Different Levels
• The study of life can be divided into different levels of biological organization
Levels range from molecules to the entire living planet
• New properties emerge at each level in the biological hierarchy
• All levels of biological organization interact with each other
•

The biosphere

Levels of Organization
Ecosystems

Tissues

Organs and organ systems

Communities
Organelles
Organisms

Populations

Cells

Atoms
Molecules

Organisms Interact with Each
Other and the Environment
• Organisms and their environments are affected by the interactions between them
•

A tree takes up water and minerals from the soil and carbon dioxide from the air; the tree releases oxygen to the air and roots help form soil

• Interactions between organisms and their environment form the basis of ecosystems

Sunlight
Leaves absorb light energy from the sun.

CO2

Leaves take in carbon dioxide from the air and release oxygen. O2

Cycling of chemical nutrients Leaves fall to the ground and are decomposed by organisms that return minerals to the soil. Water and minerals in the soil are taken up by the tree through its roots.

Animals eat leaves and fruit from the tree.

Living Organisms Need
Energy for Life’s Activities
• Energy is required for “work”
•

Movement, growth, reproduction, etc.

• Living organisms transform energy from one form to another
•

Light energy → chemical energy → kinetic energy

• Energy