Download Darwin and Evolution

Evolution
and
Darwin
*
Evolution
• Is defined as the processes that have
transformed life on earth from it’s earliest
forms to the vast diversity that characterizes
it today.
• A change in the genes!!!!!!!!
SCI.9-12.B-5 - [Standard] - The student
will demonstrate an understanding of
biological evolution and the diversity of
life.
*Old Theories of Evolution
• Jean Baptiste Lamarck (early 1800’s) proposed:
“The inheritance of acquired characteristics”
You would pass on to your children a skill you
learned. If you played the piano, your children
would be born playing the piano.
• “Use – Disuse” He proposed that by using or not
using its body parts, an individual tends to
develop certain characteristics, which it passes
on to its offspring.
“The Inheritance of Acquired
Characteristics”
• Example:
A giraffe acquired its long neck because its
ancestor stretched higher and higher into the
trees to reach leaves, and that the animal’s
increasingly lengthened neck was passed on
to its offspring.
*Lamarck’s Theory of
Evolution
• Use & Disuse -
Organisms Could
Change The Size Or
Shape Of Organs By
Using Them Or Not
Using Them
• Blacksmiths & Their
Sons (muscular arms)
• Giraffe’s Necks
Longer from
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stretching)
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Charles Darwin
– Influenced by Charles Lyell who published
“Principles of Geology”.
This publication led Darwin to realize
that natural forces gradually change
Earth’s surface and that the forces of
the past are still operating in modern
times.
*Charles Darwin
• Darwin set sail on the H.M.S. Beagle (1831-1836)
to survey the south seas (mainly South America
and the Galapagos Islands) to collect plants and
animals.
• On the Galapagos Islands, Darwin observed
species that lived no where else in the world.
• These observations led Darwin to write a book.
HMS Beagle’s Voyage
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The Galapagos Islands
• Small Group of Islands 1000 km West
of South America
• Very Different Climates
• Animals On Islands Unique
• Tortoises
• Iguanas
• Finches
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The Galapagos Islands
• Volcanic islands off
the coast of South
America
• Island species varied
from mainland
species & from
island-to-island
species
• Each island had long
or short neck
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tortoises
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The Galapagos Islands
• Finches on the islands resembled a
mainland finch
• More types of finches appeared on the
islands where the available food was
different (seeds, nuts, berries,
insects…)
• Finches had different types of beaks
adapted to their type of food gathering
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*Charles Darwin
• Wrote in 1859:
“On the Origin of Species
by Means of Natural Selection”
• Two main points:
1. Species were not created in their present
form, but evolved from ancestral species.
2. Proposed a mechanism for evolution:
NATURAL SELECTION
*Natural Selection
• Individuals with favorable traits are
more likely to leave more offspring
better suited for their environment.
Example:
English peppered moth (Biston
betularia)
- light and dark phases
*Darwin’s 5 points
1. Population has variations.
2. Some variations are favorable.
3. More offspring are produced than
survive
4. Those that survive have favorable
traits.
5. A population will change over time.
• SCI.9-12.B-5.1 - [Indicator] Summarize the process of natural
selection.
*Artificial Selection
• The selective breeding of domesticated
plants and animals by man.
• Question:
What’s the ancestor of the domesticated dog?
• Answer: WOLF
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*Evidence of Evolution
1. Biogeography:
Geographical distribution of species. EX.
Most marsupials live in Australia.
2. Fossil Record:
Fossils and the order in which they appear
in layers of sedimentary rock tells us the
order that they appeared on earth (strongest
evidence).
Eastern Long Necked Turtle
*Evidence of Evolution
3. Taxonomy:
Classification of life forms.
4. Anatomy:
• Structures that are similar because of
common ancestry (comparative anatomy)
• Vestigial structures (remnant or leftover)
structures that now have no function (human
appendix)
Homologous Structures
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SCI.9-12.B-5.5 - [Indicator] - Exemplify
scientific evidence in the fields of
anatomy, embryology, biochemistry,
and paleontology that underlies the
theory of biological evolution.
*Evidence of Evolution
5. Comparative embryology:
During the early development of
organisms very similar structures appear
in different organisms. Ex. At one point,
humans have gill slits and webbed fingers.
6. Molecular biology:
DNA and proteins (amino acids) cow
insulin was once used to treat humans
with diabetics
Evidence for Evolution - Comparative Embryology
Similarities In Embryonic Development
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Human Fetus – 5 weeks
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Chicken
Turtle
Rat
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Similarities in DNA Sequence
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*
Population
• A localized group of individuals belonging to
the same species.
Species
• A group of populations whose individuals
have the potential to interbreed and produce
viable, fertile offspring.
Evolution
of
pesticide
resistance
in
response
to
selection
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Evidence for Evolution – Evolution Observed
Evolution of drug-resistance in HIV
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*Gene Pool
• The total collection of genes in a
population at any one time.
*Microevolution
• A change in a population’s gene pool
over a secession of generations.
• Evolutionary changes in species over
relatively brief periods of geological time.
*Five Causes of Microevolution
1. Genetic drift:
Change in the gene pool of a small
population due to chance.
Two examples:
a. Bottleneck effect
b. Founder effect
*a. Bottleneck Effect
• Genetic drift (reduction of alleles in a population)
resulting from a disaster that drastically reduces
population size.
• Examples:
1. Earthquakes
2. Volcanoes
*b. Founder Effect
• Genetic drift resulting from the colonization
of a new location by a small number of
individuals.
• Results in random change of the gene pool.
• Example:
1. Islands (first Darwin finch)
SCI.9-12.B-5 The student will
demonstrate an understanding of
biological evolution and the diversity
of life.
SCI.9-12.B-5.4 - [Indicator] - Explain
how genetic variability and
environmental factors lead to
biological evolution.
*Five Mechanisms of Microevolution
2. Gene Flow:
The gain or loss of alleles from a
population by the movement of individuals
or gametes.
• Immigration or emigration.
*Five Causes of Microevolution
3. Mutation:
Change in an organism’s DNA that
creates a new allele.
4. Non-random mating:
The selection of mates other than
by chance.
5. Natural selection:
Survival of the fittest
• http://highered.mcgrawhill.com/sites/9834092339/student_view
0/chapter20/animation__mechanisms_of_evolution.html
SCI.9-12.B-5 The student will
demonstrate an understanding of
biological evolution and the diversity
of life.
SCI.9-12.B-5.4 - [Indicator] - Explain
how genetic variability and
environmental factors lead to
biological evolution.
Modes of Action
• Natural selection has three modes of action:
1. Stabilizing selection
2. Directional selection
3. Diversifying selection
Number
of
Individuals
Small
Large
Size of individuals
1. Stabilizing Selection
• Acts upon extremes and favors the
intermediate.
Number
of
Individuals
Small
Large
Size of individuals
Continuing our oyster example, very light-colored or
very dark-colored oysters might be more frequently
preyed upon by shore birds, simply because they are
more obvious on the oyster bar; as a result, the
intermediate hues become more common.
2. Directional Selection
• Favors variants of one extreme.
Number
of
Individuals
Small
Large
Size of individuals
If thicker-shelled oysters are more resistant to
breakage than thinner-shelled oysters, crabs will be
less able to prey upon them, and thicker-shelled
oysters will be more likely to survive to reproduce
3. Diversifying or
Disruptive Selection
• Favors variants of opposite extremes.
Number
of
Individuals
Small
Large
Size of individuals
This might happen in shallow water among rocks. Lightcolored oysters are more camouflaged. (less easy for a
predator to see) because they match the rock color.
Dark-colored oysters blend into the shadows cast by the
rocks. In this case, intermediate-colored oysters would
be most heavily preyed upon by the crabs, and very
light and very dark oysters would survive to reproduce.
Evidence for Evolution – Evolution Observed
Selection against small guppies results in an increase in
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average size
SCI.9-12.B-5 The student will
demonstrate an understanding of
biological evolution and the diversity
of life.
SCI.9-12.B-5.4 - [Indicator] - Explain
how genetic variability and
environmental factors lead to
biological evolution.
Video clip on Selection
• https://www.youtube.com/watch?v=64J
UJdZdDQo
Evidence for Evolution – Evolution Observed
Selection against small guppies results in an increase in
60
average size
SCI.9-12.B-5 The student will
demonstrate an understanding of
biological evolution and the diversity
of life.
SCI.9-12.B-5.4 - [Indicator] - Explain
how genetic variability and
environmental factors lead to
biological evolution.
*Speciation
• The evolution of new species. There is a
new species when an organism cannot breed
back to the parent species and produce fertile
offspring.
*Reproductive Barriers
• Any mechanism that stops two species from
producing fertile and/or viable hybrid
offspring.
• Two barriers:
1. Pre-zygotic barriers
2. Post-zygotic barriers
*1. Pre-zygotic Barriers
a. Temporal or seasonal isolation:
Breeding occurs at different times for
different species.
One species of a fish reproduces in the spring
while another reproduces in late summer.
b. Habitat isolation:
Species breed in different habitats.
c. Behavioral isolation:
Little or no sexual attraction between
species. Birds and courtship
*1. Pre-zygotic Barriers
d. Mechanical isolation:
Structural differences prevent gamete
exchange.
e. Gametic isolation:
Gametes die before uniting with gametes
of other species, or gametes fail to unite.
Chromosome numbers don’t match up.
SCI.9-12.B-5 The student will
demonstrate an understanding of
biological evolution and the diversity
of life.
SCI.9-12.B-5.4 - [Indicator] - Explain
how genetic variability and
environmental factors lead to
biological evolution.
*2. Post-zygotic Barriers
a. Hybrid inviability:
Hybrid zygotes fail to develop or fail to
reach sexual maturity.
b. Hybrid sterility:
Hybrid fails to produce functional gametes.
c. Hybrid breakdown:
Offspring of hybrids are weak or infertile.
*Interpretations of Speciation
• Two theories:
1. Gradualist Model (Neo-Darwinian):
Slow changes in species overtime.
2. Punctuated Equilibrium:
Evolution occurs in spurts of relatively
rapid change.
Time
(a)
Figure 24.13
Gradualism model. Species
descended from a common
ancestor gradually diverge
more and more in their
morphology as they acquire
unique adaptations.
(b)
Punctuated equilibrium
model. A new species
changes most as it buds
from a parent species and
then changes little for the
rest of its existence.
*Convergent Evolution
• Species from different evolutionary branches
may come to resemble one another if they live in
very similar environments.
• Example:
1. Ostrich (Africa) and Emu (Australia).
2. Sidewinder (Mojave Desert) and
Horned Viper (Middle East Desert)
*Divergent Evolution
When a group of organisms starts
living together but become separated
into different habitats. They can
evolve into different species
Darwin's finches are a clear and famous example of
divergent evolution, in which an ancestral species
radiates into a number of descendant species with both
similar and different traits.
SCI.9-12.B-5 The student will
demonstrate an understanding of
biological evolution and the diversity
of life.
SCI.9-12.B-5.4 - [Indicator] - Explain
how genetic variability and
environmental factors lead to
biological evolution.
*Coevolution
• Evolutionary change where two or more
species change to depend on each other
• Example:
1. Acacia ants and acacia trees
https://www.youtube.com/watch?v=Xm2qdx
VVRm4
2. Humming birds and plants with flowers
with long tubes
• SCI.9-12.B-5.3 - [Indicator] - Explain
how diversity within a species increases
the chances of its survival.
• SCI.9-12.B-5.4 - [Indicator] - Explain
how genetic variability and
environmental factors lead to biological
evolution.
• SCI.9-12.B-5.7 - [Indicator] - Use a
phylogenetic tree to identify the
evolutionary relationships among
different groups of organisms.
•