Introduction to Evolution

Chapter 15Standards 8a, 8b and 7d

15-1 The Puzzle of Life’s Diversity

• Evolution is a theory

–Scientists have accumulated significant evidence that modern organisms were produced by changes over time.

• Evolution: the process by which a species changes over time resulting from environmental pressure.

Who was Charles Darwin?• Lived 1809-1882• Educated in biology and natural history

• Traveled the world by sea

• The plant and animal life he saw on many of the remote islands he visited, peaked his curiosity.

•Studied live animals & fossils

Darwin’s Observations• Amazed by the number of different

types of plants and animals he saw on his travels…..DIVERSITY!

• Puzzled by where different species lived and did not live.

• Noticed all organisms had traits to help them survive in their environment.

Galapagos Islands• Darwin visited small islands west of

South America.

• Islands were very close, yet have very different climates.

• Darwin was fascinated by the diversity of animals found on each island.

• Famous research on the birds and tortoise populations.

15-3 Darwin’s Conclusions• Famous book “On the Origin of Species”

–Explained his answers to the question “Why is it that way?”

–Based on research from his travels

–Published 25 years after he returned

• Famous for theory of Natural Selection

Natural Selection• Individuals that are better suited

to their environment will survive and reproduce most successfully.

• Those that are not well suited will die off and not reproduce.

“Survival of the Fittest”

What is Fitness?

• Fitness: An organism’s ability to survive and reproduce in a given environment based on its physical traits and behaviors.–An organism that is well suited

to a certain environment has a high level of fitness.

Adaptation• Adaptation: any inherited

characteristic that allows an individual to better survive and reproduce in a given environment–Tiger’s camouflage stripes

–Polar bear’s thick fur and fat

–Eagle’s talons and beak

Diversity of Life• Species – A group of similar

organisms that can breed and produce fertile offspring.–Presently about 3 - 20 million species

on earth.

–More than 99.9% of the species that have inhabited Earth are now extinct.

Diversity• Diversity- variety of living things

–Populations with many different species (diversity) are more likely to survive.

–Variation within a specific species increases the likelihood that at least some members will survive.• Sexual Reproduction INCREASES Diversity• Asexual Reproduction DOES NOT!!