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Evolution Nothing in Biology makes sense except in the light of
evolution- Theodosius Dobzhansky
Darwin Charles Darwin Born 1809, Death 1882 Naturalist, family
man, married to cousin Emma and had 10 children. Published On the
Origin of the Species in 1859 after collecting evidence and
developing the theory for many decades. His theory of evolution by
natural selection has held true and is supported by an overwhelming
body of evidence. Despite the evidence it has remained a
controversial theory and has changed in popularity over the years.
Evolution= change over time in a population in traits.
Variation The color of human eyes, skin and hair is primarily
controlled by the amount and type of a pigment called melanin.
Specialized cells known as melanocytes produce the melanin, storing
it in intracellular compartments known as melanosomes. The overall
number of melanocytes is roughly equivalent for all people, however
the level of melanin inside each melanosome and the number of
melanosomes inside a melanocyte varies. The total amount of melanin
is what determines the range of hair, eye and skin colors.
Differential Reproduction While evidence is still being
collected, most scientists agree that the natural selection for the
lighter eye colors are linked to the relaxation of selection for
the darker skin tones. As human ancestors began to migrate to
various places around the world, the pressure for selection of dark
skin color was not as intense. Particularly unnecessary to human
ancestors that settled in what are now the Western European
nations, selection for dark skin and dark eyes was no longer
necessary for survival. These much higher latitudes afforded
different seasons and no direct sunlight like near the equator on
the continent of Africa. Since the selection pressure was no longer
as intense, genes were more likely to mutate.
Heredity Right now there are three known gene pairs that
control eye color. The bey 2 gene on chromosome 15 contains a brown
and blue allele. Also on chromosome 15, the bey 1 gene is the
central brown gene. On chromosome pair 19 the gey gene contains a
green allele and a blue allele. A green allele is dominant over a
blue allele, and a brown allele is dominant over both green and
blue alleles. For the bey 2 gene if a person has a brown allele
then they will have brown eyes. In the gey gene the green allele is
dominant over the blue allele, but it is still recessive next to a
brown allele. For example if a person has a brown allele on
chromosome 15, but all the other alleles are blue or green, they
will have brown eyes. A green eyed person would have a green allele
on chromosome 19 and all or some other blue alleles. Blue eyes are
produced only with two blue eye genes. All four alleles must be
blue to produce a blue eyed person.
Natural Selection- Postulates 1. variation of the trait within
a population 2. certain variations of the trait confer a fitness
advantage to the individual that has them which allows those that
have fitness to reproduce. 3. this trait variety is passed on to
Micro-Evolution Microevolution is evolution on a small scale
within a single population. Mechanisms: Mutation, Genetic Drift,
Migration, Natural Selection.
Macro-Evolution Macroevolution generally refers to evolution
above the species level. Mechanism: Microevolution + time!
Evidence 1.) Fossil Record-the ordered array in which fossils
appear within layers of sedimentary rocks. 2.) Comparative
Anatomy-comparison of body structures in different species, which
give signs of common descent 3.) Biogeography-the geographical
distribution of species 4.) Comparative Embryology-the comparison
of early stages of development 5.) Comparative Molecular
Biology-comparison of DNA, RNA and Protein sequences in difference
species, which gives signs of common descent on the molecular level
6.) Population Genetics- using allelic frequencies to show
evolution among a population of a species.
Fossil Record Every fossil ever found supports the theory of
evolution by natural selection. http://www.agiweb.org
/news/evolution/exam plesofevolution.html http://www.agiweb.org
Comparative Anatomy Sexual dimorphism- males and females in a
species that look different. http://www.blackwellp
ublishing.com/ridley/a- z/sexual_dimorphism.a sp
http://www.blackwellp ublishing.com/ridley/a- z/sexual_dimorphism.a
sp Organisms that are closely related to one another share many
anatomical similarities. All comparative anatomy studies ever done
support the theory of evolution.
http://science.jrank.org/pages/348/An atomy- Comparative.html
http://science.jrank.org/pages/348/An atomy- Comparative.html
Comparative Anatomy cont Vestigial Structures- non functional
trait from a past ancestor http://evolution.about.
com/od/evidence/tp/ Vestigial-Structures-In- Humans.htm
Vestigial-Structures-In- Humans.htm Homologous morphology and
function http://evolution.be rkeley.edu/evolibra
ry/article/0_0_0/line s_05 http://evolution.be rkeley.edu/evolibra
Comparative Anatomy cont convergent evolution-when two
different species have adaptations for a common environment, giving
them analogous structures (structures that look & function the
same way, but have different genetic makeup) divergent
evolution-when you have a common ancestor and different adaptations
in different environments leads to new species, but homologous
structures (features that often have different functions but are
structurally similar because of common ancestry)
Biogeography the branch of biology that deals with the
geographical distribution of plants and animals Speciation is a
result of natural selection and isolation.
Comparative Embryology http://www- tc.pbs.org/wgbh/ev
olution/library/04/2/p df/l_042_03.pdf http://www-
tc.pbs.org/wgbh/ev olution/library/04/2/p df/l_042_03.pdf
Comparative Embryology is the branch of embryology that compares
and contrasts embryos of different species.
Comparative Molecular Biology the greater number of DNA and
Proteins sequence similarity between species, the more likely they
share a common ancestor, more closely related (sequence homology)
Population Genetics The Hardy-Weinberg principle states that a
sexually reproducing population will have stable allelic
frequencies and therefore will not undergo evolution, given the
following five conditions: large population size no immigration or
emigration random mating random reproductive success no mutation
The Hardy-Weinberg principle proves that variability and
inheritance alone are not enough to cause evolution; natural
selection must drive evolution. A population that meets all of
these conditions is said to be in Hardy-Weinberg equilibrium. Few
natural populations ever experience Hardy-Weinberg equilibrium,
though, since large populations are rarely found in isolation, all
populations experience some level of mutation, and natural
selection simply cannot be avoided. Therefore evolution is
inevitable when any of the conditions are broken. In every
population in nature, one or more of theses conditions have been
broken and therefor evolution is inevitable.