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Evolution
by Means of
Natural Selection
Evolution
1.
2.
The process by which modern organisms
have descended from ancient organisms.
A change in the genes over time.
Old (bad) Theories of Evolution
Jean Baptiste Lamarck (early 1800’s) proposed:
“The inheritance of acquired characteristics”
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.
Charles Darwin
Influenced by Charles Lyell who published
“Principles of Geology” in 1830-1833.
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)
and to collect plants and animals.
On the Galapagos Islands, Darwin observed species that lived
no where else in the world.
Charles Darwin
• Wrote “On the Origin of Species by
Means of Natural Selection” in 1859
Two main points:
1. Species were not created in their present form,
but evolved from ancestral species.
2. Proposed natural selection as the way evolution
takes place.
Natural Selection
• More individuals are born than can
possibly survive.
• This creates competition for resources.
• There is always variation among
individuals for any particular trait.
Natural selection cont.
• These traits are heritable. They are passed
from parents to their offspring.
• Individuals with favorable traits are more
likely to survive and reproduce.
• These traits accumulate as adaptations.
Adaptation
Any trait that helps an individual
survive in its environment.
In other words…
There is a struggle for existence in which individuals
who are better suited to
the environment survive
and reproduce at higher
rates.
Survival of the fittest
Descent with Modification
Artificial Selection
Darwin used selective breeding to support his idea.
Selective breeding- when people choose
individuals with desired traits to reproduce.
Question: How many species of dog are there?
Answer: 1, Dog breeds are a human creation.
Evidence of Evolution
1. Biogeography
2. Adaptations
3. Fossil Record
4. Anatomy
5. Biochemistry
Evidence of Evolution
Biogeography- the distribution of
life around the world.
Evidence of Evolution
Adaptations1. Structural adaptations-wings, claws, etc.
2. Camouflage
3. Mimicry
Adaptations
4. Convergent evolution-species that live in
similar environments or that exploit similar
resources develop similar adaptations.
*Analogous structures are evidence of this!
Adaptations
5. Divergent evolution- species that become
isolated from reproducing together develop
different adaptations and become different
species.
*Homologous structures are evidence of this!
Evidence of Evolution
The fossil recordA history of life on earth
Evidence of Evolution
Anatomyhomologous structures- structures that share a
common ancestry but serve different functions
Evidence of Evolution
• Anatomy• Analogous Structures- structures that DO
NOT share a common ancestry but have
similar structure and function
Evidence of Evolution
AnatomyComparative
EmbryologySimilarities in
embryonic
structures and
appearance in
different species
Evidence of Evolution
AnatomyVestigial structures
Structure that serves
no useful function
in an organism but
was useful for an
ancestor.
Evidence of Evolution
Biochemistry- All life on earth uses DNA to
store and transmit genetic information.
Species
A group of similar
organisms that can
breed and produce
fertile offspring.
Population
A group of individuals of the same species living
in the same area.
Gene pool
All of the genes (alleles) in a population.
Genetic Variation
2 main sources:
1. Mutation- change in the DNA
1. Sexual reproduction results in genetic
“shuffling.”