1. Allopatric speciation: The Grand Canyon is a
geographical barrier separating the Albert and Kaibab squirrels
2. Population – a group of organisms that interbreed
Each population shares a gene pool (the different alleles
present in the population)
Each population has a relative frequency of each alleles, or
the number of times the allele occurs in the gene pool.
The frequency of alleles in a population tend not to change
unless there is an outside force causing it
3. Mutations are inheritable changes to the genotype
of an organism
Mutations occur randomly and spontaneously within a
population
Most mutations are harmful, but some are useful
Mutations can affect allele frequency in a population by
1. Adding new alleles for a trait
2. Changing the amount of each allele present
It can take a long time to eliminate a mutation and a
long time for a new mutation to become prevalent
4. There are 5 mechanisms that can change the
allele frequencies in a population
1. Mutation
2. Migration
3. Genetic Drift
4. Non-random Mating
5. Natural Selection
5. Movement into and out of a population can
change the allele frequency in a population’s
gene pool
Immigration can ADD individuals with variations
to the population
Emigration can REMOVE individuals with
variations from a population. Can you think of
large human immigrations and emigrations within
the last 150 years?
Many species encourage migration which can
cause more gene flow which is the process of
transferring genes among different populations
6. Genetic drift is the random changes in
allele frequency due to population size.
In
smaller populations the allele frequency
can change more rapidly than in larger
populations
7. The founder effect
occurs when a few
individuals from a larger
population colonize a
new area.
• Ex. Amish community.
The allele frequency
of this population may
differ from the larger
population because of the
limited number of individuals
8. Havinga limited number of individuals can
also impact mating.
Non random mating can influence allele
frequencies because:
• Mates can be limited by geography
• Mates can be chosen for their traits
• Mates can be more closely related to one another
9. Natural selection is process by which individual
which are more fit for the environment survive
and reproduce
The interaction of populations and the
environment results in changing allele
frequencies
There are 4 different types of natural selection:
a. Stabilizing Selection
b. Directional Selection
c. Disruptive Selection
d. Sexual Selection
10. Stabilizingselection occurs when
individuals with the average form of the
trait are most fit for the environment and
extreme traits are eliminated
This
is the most common form of selection
and works in all populations at all times
11. Lizard body size:
• Large lizards are easily seen by predators, but smaller
lizards cannot run as fast to escape the predators
• Mid sized lizards are most fit in the environment, so
they survive and reproduce more often, changing the
allele frequencies in the population
12. Directionalselection occurs when
individuals with one extreme of variations
are the most fit in the environment.
Thiscauses a gradual shift in allele
frequency to that extreme.
13. Anteater tongue length:
• Anteaters with long tongues are most fit because
of the depth of the nests of the termites they eat.
14. Disruptive selection occurs when both extremes of
variations are the most fit
There is selection against the middle variations
Ex: Limpet shells
• Dark limpets blend with bare rocks
• Light limpets blend with barnacle covered rocks
• Tan limpets are visible in both situations and get preyed
upon by birds
15. Sexual selection is the competition for
mates within a population causing
differences to occur in the allele
frequencies of the 2 genders
Matestend to be chosen for their
phenotypes and females tend to choose
the males.
16. Ex: Peacocks
• Male peacocks have large tail
feathers that make it difficult to
fly and escape from predators
• Female peacocks choose males
based on their tail feather length
and fullness
• Over time males with larger tail
feathers reproduce more
causing large tails to be selected
for
• Sexual Selection in Peacocks (3
min.)
17. In evolutionary
biology, adaptive
radiation is the
evolution of
ecological and
phenotypic diversity
within a rapidly
multiplying lineage.
18. Coevolutionary
relationships mainly
occur between
plants and
herbivorous insects
and between plants
and pollinating
insects.
Mutually beneficial
relationship.
19. When organisms evolve similar
(analagous) structures or
functions even though their
evolutionary ancestors are very
dissimilar or unrelated.
Example:
The complex eyes of vertebrates,
cephalopods (squid and octopus),
cubozoan jellyfish, and
arthropods (insects, spiders,
crustaceans) evolved separately,
but all perform the function of
http://images.sciencedaily.com/2009/06/0
vision
90601182828-large.jpg
http://jeffvrabel.files.wordpress.com/2011/08/wolf-spider-5-29-08-
7eyes.jpg
20. Look at the cladogram
at the right. What
conclusions can be
drawn about the
relationship between
humans and chimps?
21. Note that this diagram
is also a timeline. The
older organism are
located on the bottom
of the tree.
The four descendents
at the top of the tree
are DIFFERENT
species. This is called
SPECIATION.
22. Branches on the tree represent
SPECIATION, the formation of a new
species.
The event that causes the speciation is
shown as the fork of the “V”.
23. Did humans evolve from
chimps? No
What familial relationship is
a good description of the
relationship between
chimps and humans?
Distant Cousins
Are humans more highly
evolved than chimps?
NO- since the lineage is
split, each species has
evolved unique traits.
24. With 98.4% similar genetic
sequences chimpanzees are both a
link to Kingdom Animalia and our
kin.
Anima: James Balog
images used with permission. http://www.jamesbalog.com/