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!!