Download gene pool

Biology Warm-up
Sketch the diagram below. It represents a structure found
in most cells. The section labeled A in the diagram is most
likely a
A
A.
B.
C.
D.
Protein composed of folded chains of base subunits
A section of a Nucleic Acid – a gene
Part of a Lipid – fatty acid chain
A Starch made by plants
Science Fact of the Day:
There's enough gold in the Earth's crust to cover the entire
land surface knee-deep.
CO: I will analyze and evaluate the
effects of other evolutionary
mechanisms.
LO: I will write a diagram for my
notes. I will talk with my classmates
about other evolutionary
mechanisms.
Evolution can be defined as a change
in the gene pool over time.
A gene pool is the total number of genes of
every individual in an interbreeding
population.
There are 5 factors that can affect the
frequency of a gene in the gene pool.
1.
2.
3.
4.
5.
Genetic Mutation
Natural Selection
Small Population
Non-random mating
Gene Flow
1. Genetic Mutation:
• Changes in DNA that happen due to errors in
replication, transcription, translation, or
because of environmental factors.
– The source of all new genes/traits in a population
2. Natural Selection
• survival of the fittest
• advantageous genes are
passed on to the next
generation while harmful
genes are eliminated
• the driving force of evolution
3. Small Population
• Genetic Drift is a
random change in the
frequency of alleles in
a population. This has
an especially big
effect in small
populations.
• A) Bottleneck effectwhen a large portion
of a population dies
causing a significant
decrease in the size
of the gene pool.
3. Small Population
• B) Founder effect- when a few individuals from
a population leave and start another population
in a different location. This also decreases the
size of the gene pool in the new population.
4. Non-Random Mating
• Not all mates are created
equal.
• In many species, mates are
not selected at random.
Instead they are chosen for
specific characteristics.
Many organisms compete for
mating rites. Strong and
good-looking organisms are
typically favored.
• This limits the size of the
gene pool because only the
genes of the mating
individuals are passed to the
next generation.
5. Gene Flow
Gene flow is the movement of genes into or out of
a population.
A) Emigration- when individuals leave a
population decreasing the size of the gene pool.
B) Immigration- when individuals from a different
population enter a new population and begin
breeding. This increases the size of the gene
pool.
Effects of Gene Pool Size
• A decrease in the size of a gene pool increases
the speed of evolution and visa versa.
Scenarios
1. Amish people are required by their religion to
only marry and have children with other
Amish people.
2. The DNA sequence in a bird is changed from
ATT CCG TTG to TTA CCG TTG which changes
the beak shape from long and thin to short
and fat.
3. Peppered moths are eaten by birds. The moth
color varies from light to dark. Light colored
moths can blend in with a nearby species of
tree. In the 1800s factories released large
amounts of soot, which changed the tree color,
so the birds were able to more easily find the
lighter moths instead of the darker moths.
4. Northern elephant seals were hunted almost
to extinction by people in the 1890s. The
remaining population has reduced genetic
variation.
5. A lioness joins a new pride and has cubs with
the male lion.
6. A small group of birds flies from the mainland
to an island and starts a new colony. (The
birds never return to the mainland.)
Exit ticket
1. Trace your hand on a piece of computer
paper
2. Label each finger with the 5 mechanisms of
selection
3. Draw a picture for each one
4. Summarize how selection happens in a
population in 15 words in the palm of your
hand.