Download Ch. 15, Darwin`s Theory of Evolution

Chapter 15 Part 2: Evolution
Introduction Continued…
Natural Selection
• Darwin’s greatest contribution was his concept
of natural selection
• In the struggle for survival, the most fit- the
fastest prey, the strongest predator
, the one with the sharpest claws, wins the
game of survival. Survival of the fittest.
• Natural Selection – process by which
individuals that are better suited to their
environment survive and reproduce most
successfully
Evolution by Natural Selection
• Fitness = the ability to survive and
reproduce in a specific environment
• Adaptation = any inherited characteristic
that increases an organisms chance of
survival
Proof for Evolution
Beaver
Muskrat
Beaver and
Muskrat
Coypu
• Fossil record = Darwin argued that
the fossil record provided evidence
that living things have been evolving
for millions of years
Capybara
Coypu and
Capybara
They all look
like rats to me.
• Geographic Distribution of living
species:
Descent with modification, says that
similar species in similar
environments but in different
locations, were products of different
evolution paths
Homologous Body Structures
• Homologous structures all develop
from the same embryo tissues but
have different functions in the adult
organism.
Turtle
Alligator
Ancient lobe-finned fish
Bird
Mammal
Vestigial organs
• Why do we need our appendix?
• It’s useless now, but it may have served some
function in our past
• Vestigial organs = organ with little or no
function, left over from the past, ex. appendix
If you can live without
it, with no medical
help, then it’s useless!