Download Journal #4- Darwin described natural selection in his book, On the

Journal #3- Darwin described
natural selection in his book, On the
Origin of Species, in the following
way: “I have called this principle by
which each slight variation, if useful,
is preserved, by the name Natural
Selection.”
-What did Darwin mean by the
terms variation and preserved?
*Illustrate: Adaptation, Survival of
the Fittest, and Natural Selection
15-3 Darwin Presents His Case
(Interactive 378-386)
Darwin's Findings



The Galapagos “mockingbirds” were actually 3
different species found nowhere else
The brown birds were all finches. (Darwin
thought they were wrens, warblers, and
blackbirds)
The island animals found on the Galapagos
looked a lot like the ones found on the South
American Mainland, but were different species
Publication of
On the Origin of Species



Darwin waited over 20 years to publish his
findings
1858 Alfred Russel Wallace wrote a short essay
on Evolutionary change
1859 Darwin published
On the Origin of Species


Explained how evolution occurs
through natural selection
Very controversial at the
time/ Now???
Inherited Variation & Artificial
Selection


Heritable or Genetic variation is used to
improve crops or livestock
Artificial Selection

Nature provides the variation

Humans select those that are useful to produce
Evolution by Natural Selection


Struggle for Existence

High Birth rates

Competition for resources
Survival of the Fittest


The ability to survive and reproduce in the given
environment
Result of adaptations that increase survival

Organisms with these adaptations live to produce more
offspring while those that do not have them die or have
few offspring
Natural Selection cont...



Results in changes in the inherited
characteristics of a population
These changes increase a species' fitness in it's
environment
Descent with modification



Over long periods
Species change features as a result of occupying
new habitats
Each descended from other species
Common Descent



The theory that all
organisms descended
from a common
ancestor
Tigers, panthers,
cheetahs
Farther back: a
single tree of life that
links all living things
Evidence of Evolution

Fossils


Distribution of Living Things around the world


Animals in similar environments in different parts
of the world had similar features
Homologous (similar) body structures


Showed life on earth has changed over time
ex. the arms, wings, legs, fins of reptiles, birds,
and mammals are all constructed from the same
basic bones
Similarities in Embryology

Embryos of varying life forms look very similar
during development
Fossil Evidence
Geographic Distribution
Homologous Body Structures
Similar Embryonic Development
Darwin's 5 Points





Populations have variations (individual
differences)
Some variations are favorable (best suited to
their environment)
Organisms produce more offspring than can
survive, and they must compete for resources
Those that survive have favorable traits and
produce more offspring to carry the trait or traits
A population will change over time