Transcript Evolution “Change Over Time”

Evolution
“Change Over Time”
June 6th and 7th
Dr. Block and Mr. Libretto
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I. Charles Darwin
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Discovered the theory of evolution which we base the
modern theory on today.
First person to define natural selection as the driving force of evolution.
His theories threatened the ideas proposed by religion and was very
different than theories before.
Researched the wildlife of the Galapagos Islands, where he saw similarities
between the species there.
He was reluctant to share his ideas because it was different than what
people believed, and suggested a relationship between humans and other
organisms.
If Darwin was right, this meant that humans were related to other primates
(monkeys, etc.) and that they were a result of evolution, not religion.
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II. Evidence for Evolution
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1st Source - Fossil Record
The organisms alive in the past are much
different than the organisms alive today.
Life on Earth changes over time.
The modern theory uses fossil records to
identify intermediate species. This uses
identifiable similarities and differences
located on the fossils.
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II. Evidence of Evolution
2nd Source – Embryonic Development
(AKA: Comparative Embryology)
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Related organisms
look identical during
early development.
The similarities in
organisms during
development suggest all
life on Earth is related.
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II. Evidence of Evolution
3rd Source – Homologous Structures
 Two body parts with similar structure but
serve different functions.
Ex – The fin of a whale and arm of a human
have a very similar bone structure, but
have adaptation to fit different
environments.
 This shows there is a relationship between
species. (Common Ancestor)
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Homologous Body
Structures
Turtle
Alligator
Bird
Mammals
Typical primitive fish
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II. Evidence of Evolution
(Modern theory)
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4th Source – Molecular Similarities
All living things on Earth use the same
DNA and RNA code.
All living things build proteins and use
DNA or RNA to store their genetic
material.
Darwin was not aware of this evidence,
since DNA wasn’t identified yet.
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The Modern Theory of Evolution uses all of these as
Evidence of Evolution
Evidence of
Evolution
includes
The fossil record
Geographic
distribution of
living species
Homologous
body structures
Similarities
in early
development
which is composed of
which indicates
which implies
which implies
Physical
remains of
organisms
Common
ancestral
species
Similar genes
Similar genes
(Darwin didn’t know about genes.)
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III. Cladograms
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Cladograms are used to illustrate the
relationships between different species.
A cladogram is drawn based how close
two species are related.
All species on a cladogram are eventually
related to one another, some closer than
others.
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An example of a Cladogram – They can be drawn in any direction
Present
F
E
G
D
You will need to answer
questions similar to these.
C
B
A
PAST
1.
Which of the following species
has the most recent common
ancestor?
2.
Which two species are the most
closely related?
3.
Which species is now extinct?
4.
Species B is a common ancestor
for which other species?
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IV. Adaptation
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A species will change to survive in its changing
environment over time.
Abiotic Factors (nonliving factors like rain or
temperature changes) and Biotic Factors (living
factors such as availability of prey, or new
competition for food or a home) are the two
sources of environmental change that will put
pressure on a species.
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IV. Adaptation
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Each time there is an environmental
change, those individuals who cannot
survive will die, while those who can
survive, live to reproduce – this is
Survival of the Fittest.
If none of the individuals of a species has
a trait that allows the species to survive, it
will die out and become extinct.
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IV. Adaptation
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Adaptation applies to all living things:
Ex - If a colony bacteria are treated with a
powerful antibiotic, all the bacteria will
die except the few that are immune. The
immune bacteria will reproduce, their
offspring will be immune, soon the
antibiotic will be useless.
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V. Mutation
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The source of all changes in species over time.
A mutation is any change in the sequence of DNA bases.
A mutation can be at the DNA level, the gene level, or
the chromosome level.
Since DNA codes for the amino acids which build our
proteins, a change in the DNA would alter our proteins
and change our traits.
Mutations can be caused naturally by mistakes when
DNA is copied, or by environmental factors:
(Ultraviolet light, radiation, toxic chemicals, cigarette smoke, etc.)
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V. Mutation
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Depending on the environmental pressures, these
changes can be positive, negative or indifferent.
This status can change based on the changes in the
environmental pressures (Ex: Being a long necked giraffe
was not a benefit until the need arose)
A mutation of the DNA in a body cell will not carry over
to the next generation, but the mutation of a sex cell can
be passed on to offspring.
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VI. Genetic Variation
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No two people have exactly the same DNA
(except identical twins), so no two people
can show the exact same traits.
If a population has many individuals, all
with different traits, then if the
environment changes there is a better
chance that someone will have the traits
to survive.
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VI. Genetic Variation
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Ex- A very small segment of the human
population is immune to HIV. If HIV
spreads to infect every human, only those
with the immunity would survive.
If there is more variety there is more
biodiversity amongst members of a
species.
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BIODIVERSITY
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Can be thought of on the ecological level as the
difference between all living things
Can be thought of on the evolutionary
level as the difference between individuals
of one species.
Without these differences within a species,
some environmental pressures may wipe
out the entire species causing extinction.
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VII. Gene Pool
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The gene pool is the sum of all the
possible traits that exist in a species.
The larger the gene pool the more the
traits, and the better chance a species has
of surviving an environmental change.
As the gene pool becomes larger there is
more biodiversity and more genetic
variation.
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VII. Gene Pool
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As a population gets larger there will be
more mutations which both cause the
gene pool to grow.
If large numbers of a species die off or are
killed the gene pool will shrink.
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VIII. Natural Selection
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Natural Selection is the force that drives
evolution.
Natural Selection states that those
individuals with the best traits will produce
more offspring than those with bad traits.
Individuals with the best traits will outcompete other individuals for food and
other resources.
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IX. Overproduction
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All species produce more offspring than
can survive – there are limiting factors
such as food, space, competition,
predators or mates.
Only those individuals the best at getting
the resources they need will survive.
Overproduction helps ensure only the best
of a species will live.
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X. Speciation
Geographic Isolation – If a groups is separated
from the rest of their species they will evolve
separately.
 Since they can no longer reproduce with others,
they will evolve different traits to fit their
environment.
Ex – Darwin’s Finches – each species had a
different beak which was a result of the food on
that island.
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The Process of Speciation
A. Isolating Mechanisms
1. Behavioral Isolation
2. Geographic Isolation
3. Temporal Isolation
B. Testing Natural Selection in Nature
1. Variation
2. Natural Selection
3. Rapid Evolution
C. Speciation of Darwin’s Finches
1. Founders Arrive
2. Separation of Populations
3. Changes in the Gene Pool
4. Reproductive Isolation
5. Ecological Competition
6. Continued Evolution
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Reproductive Isolation
results from
Isolating mechanisms
which include
Behavioral isolation
Geographic isolation
Temporal isolation
produced by
produced by
produced by
Behavioral differences
Physical separation
Different mating times
which result in
Independently
evolving populations
which result in
Formation of
new species
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