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Speciation
February 5th 2016
Review
What are the two factors of evolutionary change
that can increase genetic variability in populations?
(2 mark)
How do they increase variability? (2 marks)
Review
Genetic variability is increased when new alleles are introduced into a population. This is achieved in Gene flow and Mutations.
Individual organisms can introduce new alleles from different populations into a new population by joining it.
Mutations can produce entirely new alleles into a population.
Review
What is the founder effect? Explain how it can lead
to evolutionary change (change in allele frequency).
(2 marks)
Review
The founder effect occurs when a part of the population splits from the original and “founds” its own population. (1 mark)
The original population may not have the same allele frequency as the original, therefore allele frequency has changed and evolution has occurred. (1 mark)
Learning Objectives … rewritten
– Explain how genetic drift can produce changes in genetic frequency (evolution)
– Describe how allele frequencies fluctuate more dramatically in smaller populations than larger ones
– Describe how genetic drift tends to decrease genetic diversity
– Define the bottleneck effect and founder effect
– Describe how mutations introduce new alleles (and sometimes traits) into a population
Learning Objectives
– Explain how new species arise in response to new
niches
– Differentiate among and give examples of
convergent evolution,
divergent evolution and speciation.
What is a species?
A distinct, identifiable group of populations whose members can interbreed. Generally distinct from other species in appearance, behaviour, habitat, ecology, genetic characteristics and etc.
Round Robin Activity
– There are a total of 6 scenarios
– In your tables, start with one and respond as best
as you can on the flipchart paper
– In 3 minutes, move to the next group.
Niches
The particular habitat
requirements of a certain
species and the role that
species plays in the
ecosystem
Speciation
The evolution of two or
more distinct species from
a single ancestral species.
All species formed by
evolution from an ancestor
Having lots of different
niches is like having a
neighborhood with lots
of different houses.
There’s something for
everyone!
Adaptive
Radiation
When populations break off
from the original (genetic
drift) to colonize a different
niche, natural selection will
select for traits that adapt
for that niche. (natural
selection)
Adaptive
Radiation
Over time, gene flow also
decreases as the
populations may no
longer interbreed.
New species are born.
Adaptive
Radiation
Another example of
adaptive radiation
include the upper limb of
tetrapods (four limbed
creatures)
Adaptive Radiation
Convergent Evolution
Convergent evolution
occurs when distinct
species adapt to a similar
environment, and evolve
similar traits.