Download Intro To Evolutionary Process

Intro to Evolution
Typically divided into 2 areas of
study…
• Microevolution-the actual processes that
allow genetic diversity to occur
• Macroevolution-measuring the success of
the changed genes
HMS Beagle
Bio-geographical Isolation!
Darwin’s 5 Key Observations:
1) Species have great fertility
2) Populations remain roughly
the same size (with a stable
environment!!)
3) Resources are limited
These mean there is a
struggle for survival among
individuals.
4) Variation is rampant.
5) Variation is heritable.
What evolution is…
• Evolutionary process deals with any
biological processes that changes the gene
sequence for a trait.
• Individuals express changes but populations
evolve!
What evolution is not…
• Changes in non-living things.
• Changes in individuals
• Microevolution is the actual change in genes
• Macroevolution is the environmental
pressures that select fittest organisms
Now that we have established what evolution is, how do
we get genes to change? There are 5 mechanisms that
result in a change in genes and new alleles to form….
1. Mutations- missense mutations
are point level changes in the
DNA. A single mutation can have
a large effect, but in many cases,
evolutionary change is based on
the accumulation of many
mutations.
2. Crossing Over- causes changes
in gene sequencing which can
change phenotype.
3. Gene flow is any movement of genes from
one population of like organisms to another.
(emigration and immigration)
• Gene flow occurs
when individuals join
new populations and
reproduce.
• This can introduce
new alleles from
neighboring
populations.
• Sometimes gene flow
keeps neighboring
populations similar.
• Gene flow decreases
the chance that two
populations will
evolve into different
species.
bald eagle migration
4. Sexual reproduction
Which egg and which sperm?
5. Genetic Drift – in each generation, some
individuals may, just by chance, leave behind
a few more. The genes of the next generation
will be the genes of the “lucky” individuals, not
necessarily the healthier or “better” individuals.
– This causes a decrease the in the number of
alleles, rather than adding something new.
Two types of genetic drift:
Founder Effect
Bottleneck
Founder effect is a type of genetic
drift.
– It occurs when a few individuals start a new
population.
– The diversity is decreased in the founded
population.
Bottleneck is another type of
genetic drift.
– It occurs when an event drastically reduces
population size.
– The bottleneck effect is genetic drift that occurs
after a bottleneck event
Genetic drift has negative effects
on a population.
– less likely to have some individuals that can
adapt
– harmful alleles can become more common due
to chance rather than the ability of the
survivor.
The occurrence of evolutionary
process is random, but the
results are not
We can’t control the 5
mechanisms of gene
change, but the drive
to produce “better”
offspring outweighs
any possible negative
outcomes.
Think about it like this:
• Genes are shuffled up using the 5 mechanisms
of evolution. (Random)
• Each sibling will be genetically unique
• The parents do not know what new combination
their offspring are getting
• Winners are determined by nature’s specific set
of rules (non-random)