THE NATURE OF SCIENCE

WHAT IS SCIENCE???

Science is the process of using observable “artifacts” to understand the world (universe) around us.

What are these “artifacts”?

• Direct observations

• Previous understandings

• Indirect observations

• Experiments

Using these artifacts (and many others), a scientist may identify a LAW or a PRINCIPLE. This is a description of some aspect of nature. For example:

• The law of gravity—describes the motion of objects in space

• Newton’s laws of motion

• The laws of genetics—describe how characteristics are passed from one generation to another

Laws differ from THEORIES. In science, a theory is an explanation of the findings of science. A law tells “what.” A theory tells “why.”

• Examples of theories:

• Atomic theory: Nobody can see an atom.

• Big Bang Theory

• Evolutionary theory—the idea that humans may be the great grandchildren of non-human ancestors.

Science uses theories to explain the nature of the universe. A valid theory is one that explains all available evidence (observations, data).

A theory is different from a hypothesis. A theory is never a guess. However, if new evidence contradicts a theory, the theory may be changed to accommodate the new evidence.

Darwin—Natural Selection

Charles Darwin sailed from England around South America, and around the southern hemisphere. By observing and collecting many types of animals and plants, he came up with a revolutionary theory of how we came to be.

Living things change over time, but these changes happen by

accident.

Zebras: African horses have a variety of colors. One day, a horse is born with white and black stripes. No reason, it just happens.

Now, let’s say several African horses are born with these stripes. This is a recessive genetic trait, but if the striped horses mate, the offspring have stripes.

Lions love to eat horses. But lions can’t find the striped horses because they blend into the tall grass. What happens over many years?

Suddenly, there are no African horses except for the striped ones. Lions run out of horses and eat other things. We have created a new species of horse (what should we call it?)

 Darwin’s conclusion: The zebra is the great grandchild of an African horse. Those horses with stripes had a selective advantage for surviving. They were selected for.

Fitness of a species means that the species has certain physical characteristics (adaptations) that allow organisms to do two things in their environment:

1) Survive (live with the environment, find food, escape predators)

2) Reproduce (find a mate, have babies)

• Darwin observed many different types of finches (birds) on the Galapagos Islands. The islands were very close together, but there were many types of finches. Darwin believed they all had a common ancestor. He called this adaptive radiation.

•  This common ancestor (he said) had offspring that mutated and migrated to the other islands.