Transcript Introduction to Evolution

Introduction to
Evolution
Chapter 15
Standards 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!!