born in Shrewsbury,
England, in 1809
studied medicine at
(1825-1827) where the
sight of blood and
anesthetics repulsed him
studied to become a
clergyman at Cambridge
recommended for a
surveying trip on the
He sailed aboard the
Beagle for 5 years,
working as a naturalist.
The Beagle sailed around the world.
This voyage lasted from 1831 to 1836.
At the time Darwin made
his trip, the majority of
people believed the
Earth and all of its forms
of life had been created
only a few thousand
years in the past.
People also believed that the Earth had not
changed during those few thousand years.
People also believed in fixity of species; in other
words, species never changed.
study of new
Darwin began to
The first dinosaur to be described
scientifically was Megalosaurus by think otherwise.
William Buckland in 1824.
James Hutton Darwin was influenced
by geologist James
The Father of Geology
Hutton’s writings that
forces he thought had
changed and were still
changing the earth.
Hutton proposed that
the Earth had to be
much more than a few
thousand years old.
Darwin was also
Lyell who wrote
Lyell’s book proposed
had shaped the Earth
such as seen in
volcanoes active in
On the voyage, Patterns in the species
Darwin noticed suggested that the
that everywhere he species had changed
went, the animals over time and had given
and plants differed rise to new and different
Many of Darwin’s
wildlife in the
Islands lie 500 miles
west of Ecuador in
the Pacific Ocean,
directly on the
“Galapagos” means turtle.
Darwin noticed on
there were several
types of finches.
finches: they all
looked like a
bird he had seen
on the South
Darwin wondered if the birds and other
animals had been created to match their
environment, why didn’t these birds look like
the birds of the African continent, since the
environments of both the Galapagos and
Africa were similar?
Darwin guessed that
some of the birds
from South America
migrated to the
Once on the islands,
the birds must have
changed over the
This would explain the numerous species of
Each species has descended, with changes,
from other species over time.
Darwin called this…
Descent With Modifications
(change in species over time)
Darwin based his theory
on his own observations
and the writings of
Malthus was a British
social scientist who
made these observations
People have more children than are
able to survive.
There are built-in population checks:
disease, famine, and war.
Darwin extended these
principles to biology, which
helped him form his theory of…
…or Survival of the Fittest.
Darwin published his ideas in the book
On The Origin of Species by Means of
Natural Selection, or the Preservation of
Favoured Races in the Struggle for Life
Five basic components of
1. All species have genetic variation.
Every species is different,
even within itself.
Look around you…are
you all the same?
2. Organisms produce more offspring than can
survive. Many that survive do not produce
The female green sea turtle lays a clutch of about
110 eggs. She may lay several clutches.
It is likely that less than 1%
of the hatchlings will ever
reach sexual maturity.
3. Since more organisms are produced than can
survive, there is competition (struggle for
Competition exists WITHIN and AMONG species.
Within and Among Species for
And Within a Species for
The constant struggle for survival is affected by
short-term natural disasters. (drought, fires,
floods, snowstorms, hurricanes, and tornadoes)
The constant struggle for survival
is also affected by long-term
changes in the environment. (ice
ages, biome shifts, etc)
4. Survival of the fittest Some organisms are
more suited to their environment as a result of
variations in the species.
Fitness: the ability of an individual to
survive and reproduce in its specific
environment. Fitness is a result of adaptations.
Individuals that are fit to their environment
survive and leave more offspring than those
He who spreads the most genes wins!
5. Decent with modification: Living species today
are descended with modifications from common
ancestral species that lived in the past.
Characteristics of fit individuals
increase in a population over time.
Over time, genes for less
favored characteristics will be
eliminated from the gene pool.
Example: giraffes and their
increasingly longer necks.
Natural Selection: Survival of the Fittest
An adaptation is any inherited characteristic (a
genetic variation) that can increase an
organism’s chance of survival.
An the variation exists first. change
organism does not
because of need or desire to
the environment changes.
survive. The organism either
already has the variation that
a variation may give an advantage
survive environmental change.
toenables it to survive or it dies.
• A group of organisms that are closely
related and naturally mate to produce
• The process by which new species form.
– Separate populations of a single species often
live in different environments
– In each environment, natural selection acts on
– If environments different enough, separate
populations can become dissimilar
Different genes favor survival in different habitats
– As two groups become more different over
time, they may be unable to breed= new
• What keeps new species separate?
• Reproductive Isolation- two populations
of the same species do not mate with each
other- can be due to…
– Geographic isolation
– Temporal isolation
– Physical differences
– Hybrid sterility
Ex. Garter snakes- some live in water, some are
Ex. Courtship behaviors
Ex. Eastern spotted skunk (late winter) and
western spotted skunk (late summer)
Ex. Differences in blossoms attract different
Ex. Gametes of red and purple sea urchins are
unable to fuse
Ex. Hybrid salamanders do not complete
development, those that do develop are frail
Ex. Donkey + horse = mule- sterile
Ex. Even if the first generation of hybrids is viable
and robust, subsequent generations are
weak or sterile- rice
As the environment changes, organisms must
have variations that allow them to survive
(adapt) to those changes or die
If an entire population of
a species cannot adapt,
that species becomes
say that the
It is estimated that 1/5 or more of the world’s
species will become extinct if the rainforests
If we are in a period of mass extinction . . .
What animals will your grandchildren be able
to see in the wild?
Visit the World Photos by MartinHarvey
Wildlife Fund website World Wildlife
for more information Fund International