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10.4 Evidence of Evolution
The Evolution of Whales Pg. 318 (Sponge # 5)
• Please read the evidence on pg. 318 showing how whales
evolved over time
• 1) Fossil Evidence: How had the Dorudon (40 million years
ago) , Ambulocetus (50 million years ago), and Pakicetus
(52 million years ago) changed over millions of years? How
are they similar and different than today’s whales?
• 2) Embryological Evidence: Looking at the whale embryo,
please explain how the nostrils differ in whales from other
land mammals.
• 3) Vestigial Evidence: Looking at the vestigial evidence,
explain why whales have a femur and pelvis.
11.1 Genetic Variation Within Population
KEY CONCEPT
A population shares a common gene pool.
11.1 Genetic Variation Within Population
Do you see any variation in this population of penguins? How
is human variation different? Can you think of another animal
that has very little variation? One with a lot of variation?
11.1 Genetic Variation Within Population
Genetic variation in a population increases the chance
that some individuals will survive.
• Genetic variation leads to phenotypic variation.
Phenotypic variation- is any observable characteristic or
trait of an organism (you can see it!) –color, size, looks
11.1 Genetic Variation Within Population
• Phenotypic variation is necessary for natural
selection.
– The greater the variation in phenotypes, the more
likely it is that some individuals can survive in a
changing environment Ex: The Peppered Moth
Moths before the pollution
Moths after pollution
11.1 Genetic Variation Within Population
• Genetic variation is stored in a population’s gene pool.
A gene pool is made up of all alleles in a population
– allele combinations form when organisms have
offspring
11.1 Genetic Variation Within Population
• Allele frequencies measure genetic variation.
– measures how common allele is in population
– can be calculated for each allele in gene pool
11.1 Genetic Variation Within Population
Attached earlobes
Tongue rolling
Hitchhikers thumb
11.1 Genetic Variation Within Population
PHENOTYPE ACTIVITY
Attached
Earlobes
YES
NO
Total Population
Tongue Rolling
Hitchhiker’s
Thumb
11.1 Genetic Variation Within Population
SPONGE
Why does genetic variation increase
the chance that some individuals in a
population will survive? (Think
Peppered Moth)
11.1 Genetic Variation Within Population
MUTATIONS
11.1 Genetic Variation Within Population
• A Mutation is a random change in the DNA of a gene.
– can form new allele
– can be passed on to
offspring if in
reproductive cells
UGUAC AUG UAU ACG UCU CAA
UGUAC AUG UAU ACG UCU CAG
11.1 Genetic Variation Within Population
Mutations- Can be positive, neutral, or negative.
Whether it is positive or negative depends on the
environment
CCR5-Δ32- gene found in
some European people, but n
in any South
African people
11.1 Genetic Variation Within Population
Genetic variation comes from several sources.
• Hybridization is the crossing of two different species.
– occurs when individuals can’t find mate of own
species
– topic of current scientific research
Liger= lion and tiger Tigon=Tiger and lion
Mule= horse and donkey
11.1 Genetic Variation Within Population
• Recombination forms new combinations of alleles.
– usually occurs during meiosis
– parents’ alleles
arranged in new
ways in gametes
–-method of DNA repair
*Can lead to offspring having a different combination of
genes than their parents