Unifying Themes of Biology

Core Unifying Theme: Evolution• The overarching theme of biology.• Evolution accounts for the unity and

diversity of life (next theme). • Evolution accounts for the match of

organisms to their environments.• Charles Darwin proposed natural selection as

the mechanism for evolutionary adaptation of populations to their environments.

Heredity

• The continuity of life depends on the inheritance of biological information in the form of DNA molecules.

• Genetic information is encoded in the nucleotide sequences of the DNA.

Diversity and Unity of Life• There are millions of different species of

living things on earth. • The continuity of life is based on DNA.• Biologists classify species according to a

system of broader and broader groups. • All of life is connected through its long

evolutionary history.

Structure and Function

• Form and function are correlated at all levels of biological organization.

• The form of a biological structure is directly related to the function of that particular structure. – A change in form = a change in function

Cells

• Cells are an organism’s basic unit of structure and function.

• The cell is the lowest level of organization that can perform all of the activities required for life.

• Cells are either prokaryotic or eukaryotic.

Emergence

•All organisms have structure and are well-organized.•New properties emerge at each level in the biological hierarchy.•New properties result from interactions among components at the lower levels.

Interdependence• Systems and Interactions

– Separate parts work together as a whole– Nothing exists in isolation

• Organisms interact with their environments, exchanging matter and energy.

Regulation

• Organisms must maintain stable internal conditions.– Conditions within normal range

• Feedback mechanisms regulate biological systems.

• Feedback is a type of regulation common to life at all levels, from molecules to the biosphere.

Energy Transfer

• All organisms must perform work, which requires energy.

• Energy powers all life processes.• Energy flows through organisms and

ecosystems.

Nature of Science• Science is a process of inquiry or a way of

knowing about the world.• The process of science includes

– observation-based discovery,– testing of explanations (controlled experiments),– hypothesis-based inquiry,– theories that provide broad explanations.

• Ideas change with new data.

Science, Technology, and Society

• Many technologies are goal-oriented.• Biological research is applied to reach

many goals.– Medicine– Agriculture– Warfare– Machine design

Great Theories of Biology

• Cell Theory• Theory of Evolution by Natural Selection• Gene Theory of Inheritance• Germ Theory of Disease• Abiogenesis