Transcript 3.1d Speciation

Starter Activity:
On a show me board sketch a short story
board to describe natural selection using
one of the examples you have learnt
about so far.
Speciation
Learning Intention:
Natural selection brings about speciation.
Different factors can separate species and
cause new species to evolve.
Success Criteria:
Explain what speciation is and what causes it
to happen.
Species
A species is a group of organisms that can
reproduce to produce fertile offspring.
Twig on Glow: Species (glossary)
The Tree of Life
http://www.open.edu/openlearn/natureenvironment/natural-history/tree-life
What is speciation?
Twig on Glow: Origin of Species
Watch the video clip and note down any
key words on your show me board.
What is speciation?
Speciation is the formation of new
species and natural selection is the
mechanism that causes it to happen. This
is the basis of the theory of evolution.
Factors involved in speciation
• Speciation is the formation of a new species
from existing species.
• This depends on random mutations causing
changes in genotype (genes) and phenotype
(physical appearance) of some individuals.
• The change allows these organisms to exploit
the environment they are in, helping them to
survive and pass on their genes to the next
generation.
Factors involved in speciation
For speciation to occur three factors
need to be involved:
1. Isolating mechanisms (to create subgroups)
2. Random mutations (favourable)
3. Natural selection
Large population of one species
Isolation by a barrier
Sub-population A
Mutation occurs
Sub-population B
mutant
mutant
Natural Selection
Two species evolve
Species A
Species B
Barrier removed. Species A cannot
breed with Species B. Speciation has
occurred.
Isolating mechanisms
1. Geographical
Can you think of any geographical barriers
that might prevent species
from exchanging genes?
Isolating mechanisms
1. Geographical
mountains
rivers
deserts
Oceans and seas
Isolating mechanisms
2. Ecological
Can you think of any ecological barriers
that might prevent species
from exchanging genes?
Isolating mechanisms
2. Ecological
temperature
pH
humidity
Isolating mechanisms
3. Reproductive
Can you think of any reproductive barriers
that might prevent species
from exchanging genes?
Isolating mechanisms
3. Reproductive
• Organisms like to
reproduce at different
times of year.
• Lack of attraction
•Sex organs are the wrong size
•Pollinating mechanisms fail
Speciation
What is speciation and what causes it?
Speciation Summary
•Speciation occurs after part of a population becomes isolated.
•Mutations occur in each sub-population.
•Natural selection selects different mutations in each group, due to
different selection pressures.
•Each sub-population evolves until they become so genetically different
they are two different species.
Key Words
Discuss the meaning of each underlined word with your partner.
Speciation
Learning Intention:
Natural selection brings about speciation.
Different factors can separate species and
cause new species to evolve.
Success Criteria:
Explain what speciation is and what causes it
to happen.
Scottish Speciation
Research and presentation task…
Scottish examples of isolation leading to speciation:
Arran Whitebeam
St. Kilda Wren
Arctic Char
Choose one of the examples above and find out how isolation has caused it to evolve
as a new species. You may present your work any way you like but you must work
towards the following success criteria:
You must include… Where the organism is found and information about it’s habitat.
You should include… How the organism is adapted to where it lives.
You could include… Explanation about how speciation has caused this new species to
evolve: What are it’s ancestors? Is it linked to another species? Why is it classed
as a new species? Any other interesting facts?