Transcript Mechanisms of Evolution part 2

Bellwork: 1/7/16 Explain why this does
NOT show evolution
• You will also
need a
pen/pencil and
your
journal/paper
today
• Have your
homework out
for me to collect
Science Fact of the Day:
There's enough gold in the Earth's crust to cover the entire
land surface knee-deep.
Essential Question:
How does evolution happen?
(you may continue your notes from
Tuesday)
I. Mechanisms of Evolution
A gene pool is the total number of genes of
every individual in an interbreeding
population.
Evolution can be defined as a change
in the gene pool over time.
Genetic Drift is a random change in the
frequency of alleles in a population due to
random sampling.
There are 5 factors that can affect the
frequency of a gene in the gene pool.
1.
2.
3.
4.
5.
Genetic Mutation
Non-random mating
Natural Selection
Small Population
Gene Flow
4. Small Population
1. Bottleneck effect- when a
large portion of a population
dies (REDUCES gene pool).
2. Founder effect- when a few
individuals from a group
leave and start another
population in a different
place (REDUCES gene pool)
A decrease in the size of a gene pool increases the
speed of evolution and visa versa.
5. Gene Flow
1. Gene flow is the movement of genes into or
out of a population.
a. Emigration- when individuals leave (EXIT) a population decreasing
the size of the gene pool.
b. Immigration- when individuals from a different population enter
(INTO) a new population and begin breeding. This increases the size
of the gene pool.
Changes in the frequency of a gene in a gene pool
leads to
Microevolution: small change over a period of time
leads to
Macroevolution: total of many changes that transform
organisms over a long period of time.
leads to
Speciation: creation of 2 different species from 1 original
species
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.)
On a separate sheet of paper…
answer the questions around the
room. Please, write the number of
the question and your answer.
Mix-Freeze-Group
Genetic
Mutation
Natural
Selection
Small
Population
Non-Random
Mating
• I am going to survive! Because I have the best genes for my
environment.
• I am HUGELY affected by genetic drift.
• I am VERY picky. I will only choose you, because your traits
are most attractive to me.
• I am a mistake in the DNA sequence
Changes in the frequency of a gene in the gene pool initially leads to
microevolution.
Microevolution refers to a small change in a population over a
short amount of time.
Many small changes eventually lead to macroevolution.
Macroevolution refers to the sum total of many changes that
transform organisms over a long period of time.
Macroevolution leads to speciation or the creation of a new species.
When an evolving population can no longer interbreed with the
original population, a new species is formed.