Transcript Modern theory of Evolution…Part4

Modern Theory of Evolution…Part4
I.
Darwin’s Weakness
•
Couldn’t explain why there was variation
in populations. Didn’t understand
genetics! Mendel’s theory was only
dominant/recessive
How do new characteristics appear?
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Mutations
Sexual reproduction
II. Modern Theory of Evolution
• Darwin’s theory of Natural Selection
with Genetics!
+
III. Population Genetics
• Species:
A group of organisms that look alike and are
capable of reproducing and creating fertile
offspring.
• Population:
A group of individuals of the same species living
in the same place at the same time.
– Ex: homo sapiens in Hawaii
– Ex: Stray cats at Kalaheo High School
Population…continued
–
Can an individual respond to
environmental change by
adding or losing a trait?
•
–
No, evolution is a change in a
species over a long period of
time in response to
environmental changes.
Populations evolve, not
individuals!!
Population Genetics…cont
• Gene Pool:
All the genes in a population at any
given time.
• Allele Frequency:
Occurrence of alleles in a population
– Remember, alleles are different forms of
the same trait.
IV. Adaptive Value Problems
• Step 1: Define the population & count it!
– ____Homo sapiens in this classroom
• Step 2: Define the trait and alleles.
– Trait: tongue rolling
– Alleles: R-tongue roller, r-non tongue roller
• Step 3: count up the genotypes in your population and
the totals of each alleles.
– RR:_______
Rr:______
rr: ______
Total R: ______
Total r:______
Total alleles:________
• Step 4: Determine the gene frequency of each allele.
– Gene frequency of “R” =(# of R)/ Total
– Gene frequency of “r” = (# of r )/ Total
Let’s try another example…
• Step 1: ____Homo sapiens in this classroom
• Step 2: ____PTC tasting…T: taster, t:
non-taster
• Step 3: TT:_____ Tt:_____ tt:_____
Total T:____ Total t:___
Total alleles______
• Step 4: Determine the gene frequency for
“T” and “t”
V. So why do these FUN problems?
•
Adaptive Values:
The value traits have in helping an
organism survive.
–
Allele frequency is the same thing
*High Value-90% *Medium value-50% * Low value-10%
 Camouflage in a tree frog
 Tongue rolling in humans
 Six fingers in humans
Adaptive Values…cont.
The more variety in a species (even neutral
variations), the greater chance for..
1.
2.
Survival… Environment is always changing
Variation fights off extinction
Once trait is lost…
1.
2.
It is really hard for a species to get it back.
Traits may not be useful now, but who knows
what will be needed in the future to survive.