Download Evidence of Evolution

Examples of Evolution
http://schoolworkhelper.net/wp-content/uploads/2010/12/cladogram.gif
Allele Frequencies
There are dominant and recessive
alleles.
Hardy and Weinberg (scientists)
determined that dominant alleles do
NOT automatically replace
recessive alleles.
Alleles in a population only change
if selection acts upon them
http://campus.murraystate.edu/academic/faculty/terry.derting/bio116/hardy_weinberg.jpg
http://www.google.com/imgres?imgurl=http://www.wallsofthewild.com/pterodactyl.jpg&imgrefurl=http://www.wallsofthewild.com/pter.htm&usg=__9caIuOdNvnUNeTtJd_BwijJIK5M=&h=479&w=800&sz=100&hl=en&start=0&zoom=1&
nid=vSsuBQ-o-EFlxM:&tbnh=131&tbnw=219&ei=6ahTYjRF6iU0QGo5JSEBQ&prev=/images%3Fq%3Dpterodactyl%26um%3D1%26hl%3Den%26rlz%3D1G1GGLQ_ENUS398%26biw%3D1438%26bih%3D680%26tbm%3Disch&um=1&itbs=1&iact=hc&vpx=1109&vpy=148&dur=1
95&hovh=174&hovw=290&tx=91&ty=85&oei=-6ahTYjRF6iU0QGo5JSEBQ&page=1&ndsp=19&ved=1t:429,r:5,s:0
HARDYWEINBERG
PRINCIPLE:
The frequencies of alleles in a
population do not change
unless evolutionary forces act
on the population.
http://www.maropeng.co.za/images/uploads/fossil_lg.jpg
Hardy-Weinberg
• Holds true for:
• large populations in which members
do not mate with relatives AND
• as long as evolutionary forces are not
acting on the population
5 Evolutionary Forces
1. Mutations
2. Gene Flow
3. Nonrandom mating
4. Genetic drift
5. Natural Selection
#1 Mutations
• Mutation rates are slow in nature
• Not all result in phenotype changes
(remember the codon wheel)
• Mutation IS the source of variation
though & makes evolution possible
• http://www.youtube.com/watch?v=Mkmt
odFQbQM
#2 Gene Flow
• The movement of individuals to or from
a population (MIGRATION) creates
gene flow.
• Immigrants = arriving individuals
• Emigrants = departing individuals
#3 Nonrandom Mating
• In-breeding alters Hardy-Weinberg
• Also occurs when organisms choose
their mates
#4 Genetic drift
• Small populations that are isolated from
one another can differ greatly because
of genetic drift
• Fires - landslides - etc.
# 5 Natural Selection
• The frequency of an allele will increase
or decrease depending on the allele’s
effects on survival and reproduction
• N.S. is one of the most powerful agents
of genetic change.
http://evolution.berkeley.edu/evolibrary/article/evo_39
Natural Selection affects the Distribution
of Phenotypes in 4 Ways!
1 – Stabilizing Selection
2 – Directional Selection
3 – Disruptive Selection
4 - Sexual Selection
1- Stabilizing Selection
• Individuals with the average form of a trait
have the highest fitness.
2 – Directional Selection
• Individuals at one end of the curve have
higher fitness and are favored more than
individuals in the middle or other end.
3 – Disruptive Selection
• Individuals with either extreme variation of
a trait have greater fitness than individuals
with the average form of the trait.
4 – Sexual Selection
• The preferred choice of a mate based on a
specific trait.
Peacocks
-- females choose
males based on
certain traits
V. I .S .T.
• V = Variation:
All life forms vary genetically within a
population. It is this genetic variation upon which selection
works.
• I = Inheritance: Genetic traits are inherited from
parents and passed on to offspring.
• S = Selection: Organisms with traits that are
favorable to their survival get to live and pass on their
genes to the next generation.
• T = Time: Evolution takes time. It can happen in a few
generations, but major change, such as speciation, often
take very long periods of time.