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Charles Darwin: Father of Evolution
EVOLUTION

Charles Darwin 1809-1882
 Very
important Biologist!!! (Father of Evolution)
 Responsible for the Theory of Natural Selection
 Wrote book: The Origin of Species
Evolution
 is supported by fossil evidence
 happens when species change over a long
period of time in response to their environment
 only occurs when the gene pool changes
 is influenced by the mechanism of Natural
Selection
4 Principles for the Theory of Natural
Selection
1. Organisms produce more offspring than
can survive
 2. In any population, individuals have
variations of traits
 3. Individuals with certain favorable traits
survive in the envrironment and pass those
traits on.
 4. Over time, offspring with certain
favorable traits (variations) will make up
most of the population and ultimately look
different from their ancestors.

Survival of the fittest
Darwin’s Studies
Upon the HMS Beagle as a naturalist, he
collected both biological (live) and fossil
specimens and found them to be quite
diverse. He tried to find possible
relationships among these specimens.
 Galapagos Islands- studied many species
of plants and animals and found them to
be unique to the islands and yet similar to
species found elsewhere.

Darwin’s Studies
Thomas Malthus helped support Darwin’s
theory by indicating that human populations
grow faster than the Earth’s food supply.
He was describing competition for food,
shelter, mates, space and ability to escape
predators.
 Recognizing Natural Selection and its effect
on populations also aided in his theory. But
without knowledge of genetics, he was
unable to really understand “why”.

Review of Terms
Artificial Selection- breeding of organisms
with specific favorable traits to produce
offspring with those traits. (ex: show dogs
and race horses)
 Species- a group of interbreeding
organisms that can produce healthy, fertile
offspring
 Population- a group of a species living
together in one location

Adaptations- inherited characteristic that aids an
organism's chance of survival in its environment.
 Structural adaptation - physical features of an
organism that help the species survive (big teeth,
claws, thorns)
 Mimicry – one species that is not harmful but
has a close external resemblance to one that
is OR when several species look the same
and they are all harmful.
 Camouflage – species that can disguise, hide,
or deceive a predator.
Camouflage and mimicry can cause populations
to increase over time.
 Physiological adaptations – can occur in only
some individuals and occurs more quickly.
(resistant bacteria, roaches, weeds)
4 Evidences of Evolution

Fossils- provide a record of
early life even though fossil
records are incomplete. The fossil
record identifies organisms
throughout the geologic time
scale.
1.
Archaeopteryx

2. Anatomy- structural similarities show
organisms evolved from a common ancestor
 Homologous
structures- structural features
with a common evolutionary origin. They are
similar in arrangement and/or function
 Analogous structures- structures that do not
have a common ancestry, but have similar
functions (not structure)
 Vestigial structures- a structure that is still
present, but is no longer needed or used.
(tailbone, appendix)
Analogous
Structures
The wings of pterosaurs (1), bats
(2) and birds (3) are analogous:
they serve the same function and
are similar in structure, but each
evolved independently.
Vestigial Structures
Blind Cave Lizards
The Human Appendix
Wisdom Teeth in Humans
Hind Leg Bones in Whales
The Wings on Flightless Birds
3. Embryology- earliest stage of
growth and development. Shared
features in embryos suggest evolution
from a distant, common ancestor.
Example: mammals, reptiles, birds
and fish all have a tail and a
pharyngeal pouch, but in fish the
pouch develops into gills and in the
others, it develops into ears, jaws
and throat.
4. Biochemistry-(Biomolecules) :
Proteins- amino acids
Nucleic Acids- DNA and RNA
Carbohydrates - sugars
Lipids - Fats
The fewer the differences in
the amino acid sequence, the
more similar their
biochemistry.
Mechanisms of Evolution
Populations, NOT individuals evolve
 Natural Selection acts on the phenotypes
in a population
 Evolution occurs as a population’s genes
and the allelic frequency changes.

 gene
pool- all the genes in the population
 allelic frequency- percentage of each allele
Populations in genetic
equilibrium are not evolving.
Any factor that affects the genes
in the gene pool can change the
allelic frequency and cause
evolution.
Mechanisms for Genetic Change:
1. Mutation- a change in hereditary
information caused by radiation,
chemicals, or simply by chance
2. Gene flow- change in the gene
pool due to migration
Mechanisms for Genetic Change:
3. Genetic Drift- alteration of allelic
frequency by chance
4. Natural Selection- changes in allelic
frequencies due to inherited
variations
Mutation, Gene Flow and
Genetic Drift have a greater
effect if the population is small.
If the population is large, these
have minimal effect.
Documented record of natural selection
in the peppered moth. This study
illustrates that a mutation must be
present before the environment changes
(illustrated by melanism preceding
pollution by soot from the burning of soft
coal, in England). Predators (birds)
eliminated most of the conspicuous
moths in each location, resulting in
adaptive changes to match the
environment in each location.
3 types of Natural Selection that
act on variations:



Stabilizing selection- favors the average
individuals causing a decrease in variations
Directional selection- favors one extreme over
the other, which can lead to more rapid
evolution.
Disruptive selection- favors both extremes,
resulting in no intermediate form which can
cause the evolution of two new species
Evolution of Species
 Speciation:
Evolution
of a new species
Occurs when members of
similar species no longer mate
within their environment.
Causes of Speciation:
Geographic Isolation: mountains and
streams force the population size to
decrease and the organisms can
breed only with each other.
Reproductive Isolation:
interbreeding organisms can no
longer mate and produce fertile
offspring.
These are all
considered to be the
same species, but
different geographic
subspecies, a common
occurrence in
widespread species.
Although each
geographical variant is
phenotypically distinct,
intermediates exist
between the
populations.
Reasons for Reproductive Isolation
Because their genetic information has
changed too much and fertilization can no
longer occur.
 Behavioral- one population mates in the
spring and the other mates in the fall
 Polyploidy- too many or too few
chromosomes due to a mistake during
Meiosis.

Evolutionary Time
Gradualism- belief in a VERY slow
evolution
 Punctuated Equilibrium- more rapid
(10,000 years) evolution occurs as a result
of some major environmental change
that causes evolution to occur and then go
through periods of equilibrium.
 Both of these theories are supported by
fossil evidence

Three Types of Evolution
Convergent
Divergent
Adaptive
Convergent Evolution
Occurs
when distantly
related species look alike
because they occupy similar
environments in different
parts of the world.
Divergent Evolution
Occurs
when closely
related species have
evolved to look different
due to adaptations to a
changing environment.
Divergent
Evolution
Adaptive Radiation
When
an ancient species
evolves into many
different species in order
to fit into several diverse
habitats.
Terms

Immigration - The movement of organisms to
a specific area within the same geographical
niche.


example - From an upstream aquatic
environment to further downstream.
Emigration - Pertaining to animals that are
moving away from their natural environment
into another geographical niche.
Coevolution

Two or more species having a close
ecological relationship evolve together
such that one species adapt to the
changes of the other, thereby affecting
each other's evolution.
 Example
– Cheetah and the gazelle
Things to know
Strongest evidence for evolution – DNA
 Natural Selection needs genetic variation
and sexual reproduction to occur
 Variations of phenotypes comes from
independent assortment
 Some evidences for evolution were gained
from comparative biochemistry (insulin
from cows was used in people because of
its similarities).
