Wednesday
May 3, 2017
I can:
Agenda
Catalyst

(10) Catalyst
(45) Biochemical Similarities
in Vertebrates
(15) GN: Evolution and
Genetics
(15) IP: Evolution & Genetics
explain how changes in DNA lead
to evolution
1. What is the BEST type of
evidence for evolution?
2. What type of evidence
compares nucleic acids?
3. This type of evidence has to
do with body structure.
4. This type of evidence has to
do with development of
fetuses.
HW: IP: Evolution & Genetics
Exit Ticket Review
The process by which organisms with favorable
variations reproduce at higher rates than those
without such variations is
A. Disruptive selection
B. Natural selection
C. Sexual selection
D. Directional selection
Exit Ticket Review
Natural selection is a mechanism that acts on
individuals within a population. Which is a result of
the process of natural selection?
A. The reproductive rate of the population
decreases
B. Genetic similarity within the population
increases
C. Organisms are better adapted to their
environment
D. Adverse changes to the environment become
more frequent
Exit Ticket Review
Darwin’s studies of the finches on the Galapagos
Islands suggest that the finches’ differences in
beak structure were most directly due to what?
A. The size of the island where the finches live
B. Acquired characteristics in the parent finches
C. Mating behaviors of the different finch
species
D. Adaptations of the finches to varying
environments
Exit Ticket Review
Which is the best description of how natural
selection changes a species over time?
A. Survival of the strongest organisms in the
environment
B. Elimination of the smallest organisms by largest
organisms
C. Survival of the organisms genetically best
adapted to the environment
D. Survival of the organisms that occupy the largest
area in an environment
Exit Ticket Review
1. What is the best way to determine the
evolutionary relationships between species?
A. by comparing their bone structures
B. by comparing their physical appearance
C. by comparing the amino acid sequences of
their proteins
D. by comparing fossils that resemble the
organisms to identify common ancestors
Exit Ticket Review
2. Archaeoptryx was discovered two years after
Darwin published On the Origin of Species.
Archaeoptryx had a long, bony tail like dinosaurs,
broad wings and feather like birds, and skeletal
features of both. What best describes this
evidence?
A. fossil
B. geological
C. biochemical
D. embryological
Exit Ticket Review
3. Which could give the best biochemical
evidence of evolution?
A. lipids
B. fossils
C. nucleic acids
D. carbohydrates
Exit Ticket Review
4. The forelimbs of living whales, dogs,
humans, and bats are all similar in their
arrangement and structure. What category of
evidence is exemplified?
A. fossils
B. anatomical similarities
C. biochemical comparison
D. embryological comparison
Exit Ticket Review
5. What can be inferred from the following
statement? The protein cytochrome c is found
in all aerobic organisms.
A. Living things have not evolved.
B. All living things will evolve to be aerobic.
C. Aerobic organisms evolved from a common
ancestor.
D. Anaerobic organisms will evolved into
aerobic organisms.
REMEMBER:
Evolution is CHANGE
over TIME
Evolution requires these four things (VSIT):
1. Variation – differences between individuals in a
species
Evolution acts on variation that is already
present in a population!
Evolution requires these four things (VSIT):
2. Selection – some individuals have greater fitness than
others in the environment and will survive better
A trait that is selected for is one that
is beneficial to the organism. A
detrimental trait is selected against.
I only eat
green beetles!
The brown beetles have greater fitness in this
environment, because they are not eaten. They are
able to survive and reproduce.
Evolution requires these four things (VSIT):
3. Inheritance – the traits that result in greater fitness
can be passed on to offspring
Evolution requires these four things (VSIT):
4. Time – many, many generations must pass
We can now understand how evolution works better
than Darwin ever could. Now we know genes are the
units of heredity, and they are what explain genetic
variation.
straight fur
curly fur
different DNA  different protein  different trait
Genetic variation is studied at the population level.
• In genetic terms, evolution is any change in the
relative frequency of alleles in a population
…but where does
genetic variation come
from?
the relative frequency of an allele is the number of times that it
occurs as a % of the total # of alleles in the gene pool
Genetic variation comes from two sources:
1. mutations
– does not always affect phenotype
2. gene shuffling during meiosis
– crossing-over introduces new combinations of
genes
– independent assortment creates new
combinations of traits
sometimes a mutation will not affect
the phenotype because many codons
code for the same amino acid
Remember, it is populations, not individual organisms,
that can evolve.
gray squirrel
black squirrel
Natural selection is not the only source of evolution.
Genetic drift is the random change in allele frequency due
to small population size.
aka bottleneck effect
The population
of beetles is
very small.
A catastrophic event kills
off most of the green
beetles, by chance.
Now there is a greater
frequency of the brown
allele than before due to
genetic drift.
The founder effect is an example of a bottleneck effect.
• a small group of individuals starts a new population
with a different allele frequency from the original
population
When will evolution NOT occur?
The Hardy-Weinberg principle states that allele
frequencies in a population will remain constant if, and
only if, the following conditions are met:
1. Mating is random. (Does this happen with humans?)
equal
chances?
2. Population is very large (so genetic drift can’t occur).
3. No movement into or out of the population.
4. No mutations.
5. No natural selection.
Certain species that depend on each other can coevolve.
Coevolution occurs when the evolution of one species
affects the evolution of another.