Download Evolution & Natural Selection

What types of canine do we have in Mississippi?
Did you ever wonder why we have such a variety
of different kinds of the same type animal?
Evolution & Natural
Selection
Charles Darwin

Was an English Naturalist who Developed
the theory of evolution by natural
selection.
Darwin collected most of his data during a
voyage of the H.M.S. Beagle when it
stopped at the Galapagos Islands.

The theory of evolution states that
species change over time in response
to changes in their environment.
Evidences which support the theory
of evolution by natural selection .

Fossils- which show a change in species
structures over time.
Speciation

The evolution of new species by divergent
evolution.
Evidences which support the theory
of evolution by natural selection .

Homologous structures- Indicate that
organisms share a common ancestor.
Analogous structures have the same
function, but do not have a common
evolutionary origin.
Embryo
The earliest stage of growth and
development of both plants and animals.
Evidences which support the theory
of evolution by natural selection .

Embryonic similarities– Shows
developmental similarities among
organisms.
Evidences which support the theory
of evolution by natural selection .

Vestigial structures —indicate
evolutionary changes in an organism’s
behavior or environment.
Evidences which support the theory
of evolution by natural selection .

Genetic comparisons – indicates
evolution from a common ancestor.
Evidences which support the theory
of evolution by natural selection .

Anatomical studies – indicate
evolutionary relationships.
Do we have evidence that supports
the theory of evolution today?
Yes
Drug resistance of bacteria.
 Pesticide resistance by insects.
 Herbicide resistance by weeds.
 Changes in peppered moth populations in
their allele frequencies.

Gradualism
The theory in evolution that states that
changes in species gradually occur over
time.
Punctuated Equilibrium
The theory in evolution that states speciation
occurs relatively quickly, in rapid bursts, with
long periods of genetic equilibrium in
between

On the Galapagos Islands, Darwin
observed somewhat similar species,
with traits suited to their particular
environment.
One of the adaptations that Darwin
observed was of differences in the beak
shape of finches (birds).
Based on the adaptations that Darwin
observed on finches and tortoises on the
Galapagos Islands, he wondered if each
had originated from an ancestral species.
Darwin did not base all of his research on
the Galapagos Islands. He observed many
species and their geographical location
during his voyage.
James Hutton’s and Charles Lyell’s work
indicated that the Earth is very old (4.5
billion years old). This suggested that the
Earth was old enough for evolution to
occur.
Twenty years after his findings, Darwin
published his ideas in a book titled On the
Origin of Species. He waited so long
because he was disturbed by his
findings, which challenged
fundamental scientific beliefs.
Darwin Decided to go ahead and publish his
finding because a scientist named
Alfred Wallace sent him an essay which
was very similar to Darwin own ideas.
Darwin’s Book
On the Origin of Species
 Published in 1859

Natural selection
Natural selection could not occur with out
inherited variation in species.
Natural selection can best be defined as
survival and reproduction of the
organisms that are genetically best
adapted (suited) to the environment.
There are two types of selection.
One is natural selection which produces
the best suited animals for the
environment.
The other is called artificial selection, this
process is often influenced, if not directly
chosen by man.
Is this animal’s mutation going to be selected for?”
Why do mutations occur?
Because they are the introduction of new
variation through mistakes in DNA.
Darwin called the ability of an organism to
survive and reproduce in its environment
fitness.
An adaptation is an inherited trait that
makes an organism more suitable to its
environment. It gives the organism an
advantage in its environment.
Examples of vestigial structures (seemingly
functionless organs or structures) in
humans are the:
1. Coccyx
2. Wisdom teeth
3. Appendix
In whales, and in some snakes there are
vestigial structures as well, the femur
and the pelvis
Do whales have legs?
The tenets of Natural selection as presented
by Darwin are:
1. Individuals organisms in nature differ from
one another. Some of this variation is
inherited.
2. Organisms in nature produce more
offspring than can survive, and many of
those that survive do not reproduce.
3. Members of each species must compete
for limited resources.
4. Because each organism is unique, each
has different advantages and
disadvantages in the struggle for
existence.
5. Individuals best suited to their
environment survive and reproduce most
successfully. The animals with
characteristics that are not as well suited
to their environment die or leave fewer
offspring.
6. Species change over time. Over long
periods, natural selection causes changes
in the characteristics of a species, such as
in size and form. New species form and
other species disappear.
7.Species alive today have descended with
modifications from species that lived in the
past.
One example of animals being
adapted to their environment is
camouflage.
Leaf frog
Another adaptation is mimicry.
Syrphid fly
Yellow jacket wasp
There are two types of mimicry.
In Batesian mimicry, the mimic shares
signals similar to the model, but does not
have the attribute that makes it
undesirable to predators.
 Müllerian mimicry describes a situation
where two or more species have very
similar warning and both share genuine
anti-predation attributes.

When lions prey on a herd of antelopes,
some antelopes are killed and some
escape. Which part of Darwin's concept of
natural selection might be used to
describe this situation?
Survival of the Fittest
Movement of genes into and out of a gene
pool is called migration.
Genetic drift
Random change in allele frequencies that
occurs in small populations.
Genetic Equilibrium

Refers to the alleles remaining the same
over time within a population.
Polyploid
Organisms with multiple sets of
chromosomes.
What is extinction?
Extinction is when a species has
disappeared permanently.
The theory of continental drift hypothesizes
that Africa and South America slowly
drifted apart after once being a single land
mass. The monkeys on the two continents,
although similar, show numerous genetic
differences. The biggest factor in
maintaining these differences is
geographic isolation.
Scientists have estimated that earth’s early
atmosphere consisted of :
Ammonia, Methane, Water Vapor, and
Hydrogen.
The Miller and Urey Experiment
The existence of autotrophic bacteria
changed Earth’s atmosphere by adding
oxygen to it through the process of
photosynthesis. This release of oxygen
created the ozone layer (ozone is O3)
which blocks out deadly ultraviolet
radiation from the sun. until the formation
of the ozone layer, all life had to remain in
the water.
What is an adaptation?
An inherited characteristic that gives an
organism an advantage in its environment.
An adaptation can be physical or
behavioral.
The process by which a population becomes
better suited to its environment is know as
natural selection by adaptation.
The process by which two species evolve in
response to changes in each other over
time is called coevolution. Examples
would be a plant evolving to attract its
pollinator, predators and prey, parasite
and host.
Convergent Evolution: occurs when
unrelated species occupy similar niches.
Divergent Evolution: The pattern of evolution
in which species that once were similar to
an ancestral species diverge, or become
increasingly distinct.
Why are people so interested in
Bigfoot?