Transcript Theory of Evolution

Theory of Evolution
“Nothing in biology makes sense
EXCEPT in the light of evolution.”
-Theodosius Dobzhansky
Early Evolutionary Thought

James Hutton
 Suggested
Gradualism
 Gradual change
over a long
period of time
leads to species
formation
Early Evolutionary Thought

Gould and Eldredge

Suggested Punctuated
Equilibrium
 A successful species may
stay unchanged for long
periods of time.
 Major environmental
changes may have
caused evolution to occur
in spurts
Early Evolutionary Thought

Jean-Baptiste Lamarck, 1809

Suggested the Law of Use and
Disuse
 One Of First Scientists To
Understand That Change
Occurs Over Time
 Organisms Could Change
The Size Or Shape Of Organs
By Using Them Or Not Using
Them
Early Evolutionary Thought

Lamark
 Stated that Changes Are Adaptations To Environment
acquired in an organism’s lifetime
 Said acquired changes were passed to offspring
 If body part NOT used, it deteriorated
Early Evolutionary Thought

Thomas Malthus


Wrote that human
populations are able to
increase faster than
what the food supply
can.
We do not because of
disease, war and
famine.
Early Evolutionary Thought


Charles Darwin
Naturalist aboard the HMS Beagle

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
Traveled for 5 years around the world
Made observations and collected
samples
Eventually landed on the Galapagos
Islands where he made several
observations that impacted his Theory
of “Descent with Modification”.
The Galapagos Islands

Small Group of Islands 1000 km West of South
America

Very Different Climates
The Galapagos Islands
Animals On Islands
 Tortoises
 Iguanas
 Finches
Natural Selection

When visiting on the Galapagos
Islands Darwin noticed:


Individuals that have physical or
behavioral traits that better suite their
environment are more likely to survive
and reproduce.
This theory is called Natural
Selection
Natural Selection

Finches
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Darwin noticed that there were a number of different
types of finches
All finches had physical traits that allowed them to
adapt to their environment.
For example if a finch lived on a part of the island that
was abundant in flowering plants then the finches beak
would be long and thin so that it could drink nectar.
Natural vs. Artificial Selection

Natural Selection

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
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A mechanism for change in populations.
Occurs when organisms with favorable variations
survive, reproduce, and pass their variations to the
next generation.
Organisms without these variations are less likely
to survive and reproduce.
Artificial Selection

Breeding organisms with specific traits in order to
produce offspring with identical traits
Evidence of Evolution

Anatomy

Homologous
Structures


Structural features with
a common evolutionary
origin
Can be similar in
arrangement, in
function, or in both.
Evidence of Evolution

Analogous Structures

Body parts of
organisms that do not
have a common
evolutionary origin
but are similar in
function
Evidence of Evolution

Vestigial Structures

Body structure in a
present-day organism
that no longer serves its
original purpose, but
was probably useful to
an ancestor.
Evidence of Evolution

Embryology



Study of the earliest stage of growth and
development of both plants and animals
The embryos of a fish, a reptile, a bird, and a
mammal have a tail and pharyngeal pouches
suggest evolution from a distant, common ancestor
Pharyngeal
pouches
Pharyngeal
pouches
Tail
Fish
Tail
Reptile
Bird
Mammal
Evidence of Evolution

Biochemistry

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Provides strong
evidence for evolution.
Comparing the same
hemoglobin protein in
several species reveals
a pattern.
Species that share a
common ancestor more
recently have fewer
amino acid differences.
Adaptations

Three major adaptations exist
in nature:

Mimicry
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A structural adaptation
that enables one species
to resemble another
species.
Because a yellow jacket
looks so much like a
honeybee it’s predators
often mistake it for it’s
twin and stay away.
Adaptations

Camouflage
 Adaptation that enables
species to blend with their
surroundings
 Because well-camouflaged
organisms are not easily
found by predators, they
survive to reproduce.
Adaptations
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Physiological Adaptations



Changes in an organism’s metabolic
processes
Evolve much more rapidly.
For example, some of the medicines
developed during the twentieth century
to fight bacterial diseases are no longer
effective
Antibiotic Resistance
The bacteria in a
population vary in
their ability to
resist antibiotics.
When the population
is exposed to an
antibiotic, only the
resistant bacteria
survive.
The resistant
bacteria live and
produce more
resistant bacteria.
Formation of a New Species

Speciation


Process by which new species form
Reproductive Isolation

Two populations of the same species do not breed
with one another because:
 Geographic separation
 Difference in mating periods
 Other barrier to reproduction.