Transcript Charles Darwin and Natural Selection 1

Warm up:
If the continents “Drifed” apart as
Wegener theorized, what might have
happened to the plants and animals that
were on the plates that drifted away.
Charles Darwin
1809-1882
The Father of Theory of
Evolution
Continental Drift and Biological
Charles Darwin
Born in 1809, Shrewsbury,
England
Naturalist
Studied Medicine
Degree in Theology
Buried in Westminster
Abbey
Darwin’s Theory of Evolution
• Evolution, or change over time, is the
process by which modern organisms have
descended from ancient organisms.
• A scientific theory is a well-supported
testable explanation of phenomena that
have occurred in the natural world.
Ideas that shaped Darwin’s
Thinking
• James Hutton:
• 1795 Theory of
Geological change
– Forces change
earth’s surface
shape
– Changes are slow
– Earth much older
than thousands of
years
Ideas that Shaped Darwin’s
Thinking
• Charles Lyell
• Book: Principles of
Geography
• Geographical features
•
can be built up or
torn down
Darwin thought if
earth changed over
time, what about life?
Lamarck’s Theory of Evolution
Tendency toward Perfection(Giraffe necks)
• Use and Disuse (bird’s using forearms)
• Inheritance of Acquired Traits
Population Growth
• Thomas Malthus•
19th century English
economist
If population grew
(more Babies born
than die)
– Insufficient living
space
– Food runs out
– Darwin applied
this theory to
animals
Another influential scientist
• Botanist
• Contribution:
– Essay described
evolution by
natural selection
Alfred Russel Wallace
1823 - 1913
Publication of Orgin of Species
• Charles Dawin’s
research led him to
write “The Origin of
Species” which
attempts to explain
the link and evolution
of all species on Earth
Voyage of Beagle
• Dates: February 12th, 1831
• Captain: Charles Darwin
• Ship: H.M.S. Beagle
• Destination: Voyage around the world.
• Findings: evidence to propose a
revolutionary hypothesis about how life
changes over time
Row, row, row
your boat!
• Voyage of H.M.S. Beagle
– 5 year unpaid voyage
– Darwin studied plants, animals,
collected fossils
– Found fossils of extinct animals that
were similar to modern species. On the
Galapagos Islands in the Pacific Ocean
he noticed many variations among
plants and animals of the same general
type as those in South America.
This voyage lasted from 1831 to 1836.
Many of Darwin’s
conclusions were
based on
observations of
wildlife in the
Galapagos Islands.
The Galapagos
Islands lie 500 miles
west of Ecuador in
the Pacific Ocean,
directly on the
equator.
“Galapagos” means turtle.
The Galapagos Island
• The smallest, lowest islands were hot,
dry, and nearly barren-Hood Islandsparse vegetation
• The higher islands had greater rainfall
and a different assortment of plants
and animals-Isabela- Island had rich
vegetation.
Animals found in the Galapagos
• Land Tortoises
• Darwin Finches
• Blue-Footed Booby
• Marine Iguanas
Darwin noticed
there were several
types of finches on
these islands.
In particular,
Darwin observed
something odd
about the
finches: they all
looked like a
bird he had seen
on the South
American
continent.
In all, there were 13
types of finches, some
species being confined
to only one island.
The most distinct difference among finch
species is their beaks, which are adapted for
the specific diets available on the islands.
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
Galapagos.
Once on the islands,
the birds must have
changed over the
years.
large ground
finch
woodpecker
finch
cactus finch
This would explain the numerous species of
birds present.
G. fortis
G.
fuliginosa
Camarhynchus
pauper
Cactospiza
pallida
G. magnirostris
G. scandens
C. psittacula
Cacts Finch
(nectar,eeds, blood)
C. heliobates
C. pauper
Woodpecker-like
Finch
(seeds
G. conirostris
& insects)
Geospiza difficilis
Insect-eating Finch
Platyspiza crassitrostris
Seed-eating
Finch
Vegetarian Finch
Ground Finch
Certhidea
olivacea
& C. Fusca
Tree Finch
Warbler Finch
This tree has how
many major
branches?
PHYLOGENIC TREE:
A diagram showing the
evolutionary history of a
species of an animal.
The Journey Home
• Darwin Observed that
characteristics of many plants and
animals vary greatly among the
islands
• Hypothesis: Separate species
may have arose from an original
ancestor
Living Organisms and Fossils
• Darwin collected the preserved remains of
ancient organisms, called fossils.
• Some of those fossils resembled organisms
that were still alive today.
Living Organisms and Fossils
• Others looked completely unlike any creature he
had ever seen.
• As Darwin studied fossils, new questions arose.
– Why had so many of these species
disappeared?
– How were they related to living species?
Fossils
TWO TYPES OF EVOLUTION:
Convergent Evolution: process by which
unrelated species become similar as they
adapt to similar environments.
Divergent Evolution: formation of new
species from an existing species adapting to
new environments.
What type of evolution is a phylogenic tree?
After returning from the
Galapagos and studying
all the different types of
plants & animals. Darwin
concluded new concepts
of change….
Darwin called this…
which means (change in species over time)
Darwin extended these
principles to biology, which
helped him form his theory of…
…or Survival of the Fittest.
Natural Selection & Artificial
Selection
• Natural variation--differences among
individuals of a species
• Artificial selection- nature provides the
variation among different organisms, and
humans select those variations they find
useful.
Evolution by Natural Selection
• The Struggle for Existence-
members of each species have to
compete for food, shelter, other life
necessities
• Survival of the Fittest-Some
individuals better suited for the
environment
Natural Selection
• Over time, natural
selection results in
changes in inherited
characteristics of a
population. These
changes increase a
species fitness in its
environment
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. The environment presents challenges to
survival.
There is a constant
struggle for survival.
Examples are:
Drought
Fires
Floods
Snowstorms
Hurricanes
Tornadoes
Other natural disasters
3. Organisms produce more offspring than can
survive. Competition exists WITHIN and AMONG
species.
Within a Species
Among a Species
food
food
space
space
mates
4. Individuals that are fit to their environment
leave more offspring than those who aren’t.
Darwin’s definition of fitness:
an organism which has successfully
adapted to its environment
Organisms who possess favorable traits will
leave more offspring.
In other words, he who spreads the
most genes wins!
1st
5. 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 long necks.
Therefore Darwin’s contributions:
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Provided evidence that species evolve
In 1859, he proposed the Theory of Natural
Selection to explain evolution (Survival of the
fittest)
Over time, change within species leads to the
replacement of old species by new species as
less successful species become extinct.
Some evidence from fossils may prove that
species on Earth have evolved from ancestral
forms that are extinct. (species that have
disappeared permanently.)
What is a species?
One or more populations of individuals
that can interbreed, producing fertile
offspring.
Speciation is the process by which new
species are formed over time.
Equus, the
modern horse,
evolved from the
dog-sized
Hyracotherium.
Notice it evolved
from a four-toed
front foot to the
one-toed front
foot of the
modern horse.