1 Which one of the following statements is accurate? a. Natural selection works on variation already present in a population. b. Natural selection works on non‐heritable traits. c. Individuals evolve through natural selection. d. Organisms evolve structures that they need. e. None of the statements are true. Speciation and Macroevolution • Describe the patterns found in the study of macroevolution. • Explain the concept of exaptation and describe an examples. • Explain why mass extinctions can be seen as times of great opportunity • Define the biological species concept. Explain its limitations when applied to all types of living organisms. • Describe the different types of pre‐zygotic and post‐zygotic reproductive isolating mechanisms. • Explain the process of allopatric speciation. • Explain what a cladogram or phylogenetic tree, what information does it provide and how can it be constructed Website: http://evolution.berkeley.edu/
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Transcript
1
Which one of the following statements is accurate?
a. Natural selection works on variation already present in a population.
b. Natural selection works on non‐heritable traits.
c. Individuals evolve through natural selection.
d. Organisms evolve structures that they need.
e. None of the statements are true.
Speciation and Macroevolution
• Describe the patterns found in the study of macroevolution.
• Explain the concept of exaptation and describe an examples.
• Explain why mass extinctions can be seen as times of great opportunity
• Define the biological species concept. Explain its limitations when applied to all types of living organisms.
• Describe the different types of pre‐zygotic and post‐zygotic reproductive isolating mechanisms.
• Explain the process of allopatric speciation.
• Explain what a cladogram or phylogenetic tree, what information does it provide and how can it be constructed
Website: http://evolution.berkeley.edu/
2
Are these two groups of fliestwo populations of the same species
or are they two different species?
What is a species?
‐ population or groups of populations
‐members can potentially interbreed in nature
‐ AND produce fertile offspring
‐ appearance is not important
3
Fly scenario• An event splits the original
population in two
• Generations later…
• An other event brings the groups
together
But they are not interbreeding!!!
• Speciation has occurred
• Speciation: process by which new species
come into being
New species originate as modified descendants of other species
Process of SpeciationStep 1: Genetic Isolation
gene flow between
two populations is interrupted
(populations become
genetically isolated from each other)
Step 2: Populations diverge genetically
genetic differences gradually accumulate
between the two populations
Step 3: Reproductive isolation
Some of these genetic differences (traits)
will be reproductive barriers
(traits that prevent two individuals from interbreeding with each other)