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bio evolution ppt

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Natural Selection &
Evolution
Ch. 14 & 15
Biology
Evolution
Evolution is defined as the change in a
population over time
This is not a change in an individual
(like weight loss) but in a population due
to inherited factors
A population is a group of members of
the same species living in the same
area, reproducing together
Types of Evolution
Macroevolution—how
different species are
related (and how new
species can be created)
Microevolution—
evolution within a
species (small group)
“descent with modification”
Kettlewell’s moths
would be an example
of this
As evidenced by tracing
homologous and vestigial
structures
Evidence for Evolution
Fossil Record
Law of supraposition
Comparative
Anatomy
Homologous structures
Vestigial structures
Comparative
Embryology
Stages of fetal life
Molecular Biology
Gene sequencing
Amino acid sequencing p.
304
Fossil Record
Can tell us how old
things are relative to
other fossils
Not everything makes a
good fossil
Not every environment is
good for fossil
preservation
Gaps in the fossil record
hold questions
Because there is so
much fossil evidence, it
is basis for evolutionary
thought
Homologous Structures
Show us how things
may have evolved
from one basic
plan/blueprint geared
toward a function
Called descent with
modification
Vestigial Structures
Can show us
connections to other
organisms with
similar functional
organs
Can help us trace
our evolutionary
history (what we
once were like)
Ex: human tailbones
http://www.livescience
.com/11317-top-10useless-limbsvestigial-organs.html
Comparative Embryology
Can show us how a
variety of organisms
are more distantly
related
Even if they don’t
look alike as adults,
they may have
stages as
embryos/fetuses
that show a
common
link/ancestor
Molecular Biology
Includes comparing
the gene sequencing
and amino acid
sequencing of proteins
of organisms to see
how much they have in
common
This is one of the
strongest types of
evidence for evolution
theory
Cladograms
A branched diagram
representing
ancestral
relationships between
organisms
A visual evolutionary
tree of life
Is now often based on
molecular biology
evidence (gene and
amino acid
sequencing)
Cladograms
Macroevolution
Gradualism
Small amounts of
change over a very
long period of time
Darwin’s theory
(‘descent with
modification’)
Fossil record
Punctuated
Equilibrium
Dramatically large
amounts of change
over a very short
period of time
Explains unusual gaps
in the fossil record
(dinosaur/asteroid)
Gradualism vs. Punctuated Eq.
Microevolution
Convergent evolution
When two populations
living in similar
conditions become
more and more similar
Cactus in deserts
across the globe look
similar due to similar
conditions and survival
needs
Divergent evolution
When two populations
living in very different
conditions become
increasingly different
Darwin’s finches that
migrated to different
coastal islands, all
required slightly
different beaks to get
food
Speciation
The evolutionary
process by which new
species arise
Species are groups of
individuals that
successfully mate
together
Can be due to a
variety factors, either
physical or behavioral
barriers
Geographic Isolation
Reproductive
Isolation
Geographic Isolation
When members of a
group are physically
isolated and therefore
no longer reproduce
together
It can also be that the
two subgroups are still
physically close to
each other, but do not
interbreed due to
subtle differences in
their habitats
Reproductive Isolation
Temporal isolation:
members have
different breeding
times
Behavorial Isolation:
members are not
attracted to other
members for mating
Mechanical Isolation:
the members are not
physically able to
mate
Reproductive failure:
members do mate
and a pregnancy
occurs/offspring is
created BUT the
offspring are sterile
Darwin
Wrote On The
Origin of Species
Is credited with the
theory of natural
selection as the
primary way we
explain how
evolution occurs
Shares partial credit
with Alfred Wallace
Darwin
He was greatly
influenced by his trip
to the Galapagos
Islands off the coast
of S. America
He collected many
specimens and
detailed notes/made
diagrams
His 20 years of data
is why he receives
more credit than
Wallace
Lyell’s book detailing
how land forms
gradually change over
time (Principles of
Geology) and
Malthus’ essay On the
Principal of Population
describing how
populations competed
for food and shelter
Both books impacted
Darwin’s work
Wallace
Contacted Darwin about
jointly presenting a
paper describing the
theory of natural
selection
He had arrived at the
theory of natural
selection independently
(on his own)
Darwin agreed so that
he would not be
forgotten in the
development of this
theory
They both had taken
trips to S. America and
had read the same
influential books
Darwin receives more
credit due to the
detailed notes/evidence
he had collected over
many decades of study
The Theory of Natural
Selection
Within every population exists variation
Positive variations are called
adaptations
Individuals with beneficial adaptations
live longer and therefore produce more
offspring
More offspring will show the beneficial
adaptation in the following generations
“Survival of the Fittest”
Kettlewell’s Moths
Kettlewell studied the
effects of pollution on
typically light colored
trees on a moth
population
The moth population
included light and
dark colored moths
Industrial Melanism
The term describes how
the moth population
changed over
generations to adjust to
the changing tree color
environment
This ‘current’ example
of natural selection in
action added to the
strength of Darwin’s
argument (not just
fossils as evidence)
Types of Natural Selection
Stabilizing
selection—when
the heterozygous
condition is
selected for and the
extremes
(homozygous) are
selected against
Types of Natural Selection
Directional
selection—when
the population shifts
toward one of the
extreme
(homozygous)
conditions and
away from the other
Types of Natural Selection
Disruptive
(sometimes called
sexual) selection—
when the
heterozygous
condition is
selected against
and the extremes
(homozygous) are
selected for
You decide!
Other mechanisms of evolution
Gene flow—a change in
a population due to
migration of individuals
in and out of the area
Non-random mating—
how reproductive
choices by individual
members impact a
population over time
Genetic Drift-Bottleneck effect and
Founder’s effect—how
random chance impacts
a small population
Mutation—when a
widespread genetic
mutation impacts many
members of a
population (rare)
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