Transcript Natural Selection

Charles Darwin
1809-1882
The Father of Evolution
Charles Darwin
Born in 1809, Shrewsbury,
England
Naturalist
Studied Medicine
Degree in Theology
Buried in Westminster
Abbey
After Cambridge,
Charles was
recommended for a
surveying trip on the
HMS Beagle.
The mission of the
voyage was to chart
stretches of the South
American coast.
Darwin sailed aboard
the Beagle for 5 years,
working as a naturalist.
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.
Darwin was influenced by :
• Geologist
• Contribution:
– Earth is very old
(much older than
thought)
– Earth has changed
over time
(constantly
changing)
Sir Charles Lyell
1797 - 1875
Another influential person
• Economist
• Contribution:
Thomas Malthus
1766-1834
– Populations
have the
potential to
increase faster
than the
available food
supply
Another influential scientist
• Botanist
• Contribution:
– Essay described
evolution by
natural selection
Alfred Russel Wallace
1823 - 1913
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.
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.
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:




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.
Scientific Evidence of
Evolution includes:
 Fossil
Record
 Comparative Anatomy
 Embryology
 DNA & Proteins (Biochemical
Evidence)
Fossil Record
In order for fossils to form:
 Calcium must be
replaced
 Burial must occur by
sediment
 Usually occurs in
swamps, mud, ocean
floors, tar pits, etc.
.
COMPARATIVE
ANATOMY:
Homologous structures are
characteristics which are shared by related
species because they have been inherited in
some way from a common ancestor.
Turtle
Alligator
Bird
Mammal
For example, the bones on the front fins of a whale
are homologous to the bones in a human arm and
both are homologous to the bones in a chimpanzee
arm.
Analogous Structures
similar in function but not in origin and structure
In convergent evolution, organisms evolve
similar features independently, often
because they live in similar habitats.
VESTIGIAL STRUCTURES:
structures that serve no useful purpose
organs so reduced in
size that they are
nonfunctioning
remnants of similar
organs in other
species
ex: human tailbone,
appendix, whale
pelvis
EMBRYOLOGY

Embryos of different species may appear
similar in early stages of development

ex: vertebrate
development
3 COMPARATIVE ANATOMY

Comparison of
similarities in
embryos can
show:
Relationship to a
common ancestor