Download Evolution Notes 2012

EVOLUTION
What is evolution?
• Genetically based change in phenotype
over generations
• Process in which species undergo
modifications over generations. In some
cases these changes can result in the
formation of a new species.
Why does evolution occur?
Evolution is not survival of the strongest, or
failure of the weakest. Evolution is not fair;
it's not predictable; it's not kind. Nor is it
cruel, or chaotic, or unfair, for that matter.
It's what happens when environmental
pressures change.
Michael Jon Jensen
This essay was originally presented as the Keynote Speech at the Illinois Association of College and
Research Libraries (IACRL) Biannual Meeting, Bloomington/Normal, IL, March 30, 2006.
• What changes do we
see over time & why?
• From dog sized in
rainforests to large
animals on the plains
• Its multi-toed feet,
adapted for walking
across the forest
floor, evolved into
single-toed hooves
more suited for
running over open
country
Darwin’s Voyage
DARWIN’S PRINCIPLES
• Descent with
modification
• Natural
selection
What is natural selection?
• Process
• Differential adaptations of organisms with
beneficial traits
• The environment selects for those traits
that will be passed on with greater
frequency
What is meant by variation?
What is meant by adaptation?
• Any variation that increases an organisms
chance for survival
• When does variation become an
adaptation?
• What does adaptation depend on?
The environment
Who said characteristics or traits
(variations) that are acquired in ones
lifetime and are passed on (inherited)?
Lamarck
An extension of Lamarck's ideas of
inheritance that has stood the test of time,
however, is the idea that evolutionary
change takes place gradually and
constantly
Example from Lamarck
• This weight lifter has
built up arm muscles
from working hard
• According to Lamarck
the offspring should
have strong muscles
DARWIN’S THEORY: KEY POINTS
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•
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Variations exist
Variations can be inherited
Populations tend to overproduce
There is a struggle for survival due to
limited resources
• Animals that are best fit, survive and
reproduce (fitness is relative to a specific
time and location)
• There is an evolution of the population
with the traits of the fittest becoming most
frequent.
Classic example, the Peppered
Moth
• As a result, species
must change through
time in order to
survive.
• Organism that change
most successfully,
they survive and
reproduce are the
fittest.
Antibiotic
Resistance
Endnagered species, why?
Types of Adaptations
For each of the following slides list at least
one of example of each type of adaptation
 Morphological
 Physiological
 Behavioral
WHAT ARE DIFFERENT TYPES OF
EVIDENCE TO SUPPORT THE THEORY
OF EVOLUTION?
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•
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EMBRYOLOGY
FOSSILS
MORPHOLOGY
BIOCHEMICAL (DNA)
EMBRYOLOGY
FOSSILS
HOMOLOGOUS STRUCTURES
(MORPHOLOGY)
DNA
EVIDENCE
Organisms are classified in the same
species if they are potentially capable
of interbreeding and producing fertile
offspring. In general, they must be in
the same geographical location.
Organisms may appear to be alike and be different species. For
example, Western meadowlarks and Eastern meadowlarks look almost
identical to one another, yet do not interbreed with each other—thus,
they are separate species according to this definition. The Western
meadowlark (left) and the Eastern meadowlark (right) appear to be
identical, and their ranges overlap, but their distinct songs prevent
interbreeding.
Organisms may look different and yet be the same species.
For example, look at these ants. You might think that they are
distantly related species.
In fact, they are sisters—two ants of the species Pheidole
barbata, fulfilling different
roles in the same colony.
How does a
new species
form?
•During allopatric speciation, a population splits into two
geographically isolated allopatric populations.
•New speciation starts because populations are prevented
from interbreeding.
•Scientists think that geographic isolation is a common way
for the process of speciation to begin: rivers change course,
mountains rise, continents drift, islands break away from the
main lands, habitats fragment and become unfavorable,
organisms migrate, and what was once a continuous
population is divided into two or more smaller populations
• Macroevolution is the process by which new
species are produced from earlier species
(speciation). It also involves processes
leading to the extinction of species.
• Microevolution is evolutionary change at the
level of the population, and is defined by
changes in allele frequency within the
population over time. Such changes take
place over relatively short time periods.
• Accumulated gradual changes in two
populations that preclude their interbreeding
may lead to the formation of a new species.
Microevolution: Speciation
Genetic Drift
Bottleneck Effect
3 Modes of Natural Selection
Common Example of Stablizing
Selection
Organisms may look different and yet be the same species.
For example, look at these ants. You might think that they are
distantly related species.
In fact, they are sisters—two ants of the species Pheidole
barbata, fulfilling different
roles in the same colony.
Directional Selection Rough to
Smooth
Disruptive Selection
Can’t have
Hardy
Weinberg
Equilibria
if these
are
occuring
Non Random Mating; Artificial
Selection