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.