Download Natural Selection - Madison County Schools

Where did all the elements essential for life come
from? How did they form into complex
organisms?
Chemical evolution refers to the formation of
complex ORGANIC molecules from simple
inorganic molecules through chemical
reactions.
This takes place in Earth’s oceans and lasts for
less than a billion years
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In the 1950’s two scientists recreated the POSSIBLE
conditions in Earth’s atmosphere.
This experiment showed the evolution of organic
molecules
These scientists went even further showing how
amino acids are formed
Why are amino acids so important?
More recently, meteorites have been found
containing amino acids, meaning these compounds
are found throughout space. This obviously raises
questions regarding the Miller and Urey
experiment
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This is the evolution Darwin is referring to in
his work Origin of Species
Organic evolution is the evolution of species or
groups of organisms.
The combination of chemical and organic
evolution helps explain the steps to the
formation of aerobic heterotrophs and
photosynthetic autotrophs
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It is believed that the first organisms were
heterotrophs that produced CO2 as a by
product of their metabolic processes
This gave rise to photosynthetic autotrophs,
now there is OXYGEN in the atmosphere.
Many of the anaerobic heterotrophs die, but
those that survived were able to perform
aerobic respiration
These aerobic autotrophs and heterotrophs
become the dominant species on Earth
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The process by which organisms best suited to
the environment survive, reproduce, and pass
their genes to the next generation.
Fitness -(1) Survive Longer, (2) Reproduce
More
(3) Pass on traits to next generation
Occurs in populations, not in individuals
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Organisms produce more offspring than can
survive.
Genetic Variation - Individual organisms in a
population have slight variations or
adaptations.
Individuals struggle to survive, those with
adaptations best suited to the environment are
more likely to survive.
Survivors pass on genes for the adaptations to
their offspring.
Gradually, the population changes or evolves.
Remember the theories of catastrophism and
gradualism combine to form uniformitarianism
Punctuated Equilibrium
predicts that a lot of evolutionary change takes
place in short periods of time tied to speciation
events
This is especially true for allopatric speciation
which is when a new species forms due to
geographic isolation
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Beetles living on brown tree bark are either
brown or green.
Predator (bird) can more easily see green
beetles and will catch them more often than
brown.
Brown beetles live longer and produce more
offspring, to whom they pass the gene for
brown.
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13 different species of finches on the Galapagos
Islands
Each species has a beak that is best adapted for
a certain kind of food that is found on the
different islands
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Natural selection is an “editing” process, not a
creating one
If the environment changes and there is not a
suitable phenotype to survive in the new
environment then the species will go extinct.
There is no amount of “trying” that can help you
evolve.
Nature simply “selects” the greatest physical traits
to survive in different environments and those are
passed on.
Also, what is beneficial in one environment may
not be beneficial in another.