Transcript The Theory of Evolution

The Theory of Evolution
Evolutionary biology
addresses fundamental
questions
• Why are there so many different kinds of
organisms?
• Why are organisms so proficient at life
tasks: finding food, acquiring mates, fighting
disease, and avoiding predators?
OVERVIEW: Four Main Points to
the Theory of Evolution.
1. Variation exists within populations.
2. Some individuals of a population are better
suited to their environment.
3. Over time, traits that make certain
individuals of a population able to survive
and reproduce tend to spread in that
population.
4. There is clear proof from fossils and many
other sources that living species evolved
from organisms that are now extinct.
Does Variation Exist Within the Genes
of every population or species (the
result of random mutations)?
Is this variation Heritable?
Natural Selection Acts on
These Heritable Variations of
Traits.
• Working definition of Natural Selection:
Natural Selection is the process by which
populations change in response to their
environment. Individuals better adapted to
the environment leave more offspring than
those individuals not suited to the
environment.
Do individuals who are better
suited to their environment really
leave more offspring than
others?
HOW ABOUT A REAL
LIFE EXAMPLE,
BEYOND THE
CARTOONS.
Day
Day
Day
Day
Real Life Examples of
Evolution
Natural Selection in Action
Industrial Melanism
• A hypothesis for the explaining the
increase in dark moths was formed using
Darwin’s theory of evolution by natural
selection.
• Hypothesis: The dark variety was
camouflaged on the soot-darkened bark
and so are not eaten by birds.
The Experiment
• Populations of light and dark peppered
moths were raised in the laboratory.
• Moths were marked so they could be
identified later
• Moths were released into two separate
wooded areas.
• Birmingham= Heavily polluted
• Dorset = unpolluted
Results
color variaitons in moths
45
percent of moths recoved
40
35
30
25
20
15
10
5
0
Light moths
Dark moths
Birmingham Wood
Light moths
Dark moths
Dorset Wood
Overcoming Misconceptions
The darkened trees did not cause the darker
variant of moth to appear.
The darker characteristic was already
present in the population.
The “new” environment merely favored the
survival of the darker moths.
Evidence of Evolution
Beyond the Fossil Record
How Does Anatomy and Structure
Show Evidence of Ancestry?
Comparing the anatomy of different types
of organisms often reveals basic
similarities in body structures, even though
their functions may be very different.
Common Ancestor
• A Species from which two or more species
have diverged.
Homologous Structures
• Structures that share common
ancestry.
Analogous Structures
• Analogous structures have similar forms,
but they are not due to common ancestry.
Vestigial Structures
• Vestigial structures are anatomical
structures of organisms in a species,
which have lost much or all of their
original function.
• Structures that are considered to be
evidence for an organisms
evolutionary past.
Flightless Cormorant of the Galapagos
Vestigial Pelvis of the Whale
Femur and Pelvis of Whale
How is Embryonic Development
Evidence for Evolution?
• The evolutionary history of organisms is
seen in the development of embryos.
What are some common
structures that vertebrate
embryos share?
• Tail bud
• Pharyngeal pouches
• Buds that become limbs
How are Biological Molecules a Record
of Evolution?
Species that share common ancestry
more closely, have more amino acid
sequence in common.
Species that have diverged from a distant
common ancestor have more differences
in amino acid sequences.
The Hemoglobin Protein shows common ancestry.
Hemoglobin Comparison
Species
Amino acid differences
Gorilla
1
Rhesus monkey
8
Mouse
27
Chicken
45
Frog
67
Lamprey
125
Great Moments in Evolution
What is the Fossil Record?
• Working definition: All the fossils
known to science.
• Provides snapshots of the past
• Illustrate a panorama of evolutionary
change over time
Nice Striations!
What’s a Fossil, You Ask?
• The remains or traces of once-living
things.
• shells, teeth, bones, footprints, leaf
impressions, and petrified wood.
“Endless forms most beautiful and most
wonderful” – Charles D.
Is the Fossil Record
Complete?
• No, it most certainly isn’t.
The probability that any particular organism
that once existed, is part of the fossil record
today is rare.
For
Three formation
Good Reasons.
. . event
1.Fossil
is a rare
2.Fossils survival is a rare event
3.An exceedingly small fraction of
surviving fossils will ever be found
John Day Fossil Beds
Transitional Forms in Horse
Evolution
Lahars: Pyroclastic Mud Flows