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Evolution
What is evolution?
How do new species form (speciation) and die out
(extinction)?
What evidence is there to support evolution?
Evolution
Evolution
Theory of Evolution:
• species change over time
– Caused by natural selection
• Speciation – the formation of a new species
• Causes:
– geographic isolation
– rapid environmental change
– evolution
Extinction
Dinosaurs, 66 mya
Dramatic climate
change
Dodo, 1662
domesticated animals
Passenger Pigeon, 1914
hunting by humans
Golden Toad, 1989
fungus
Extinction
• Extinct = no members of a species left
• Caused by a change in environment
–
–
–
–
Climate change
New predators
Lack of food sources
disease
• If the species does not have or develop (mutate) necessary
adaptations it will die out
EVIDENCE OF EVOLUTION
• Evolution is a theory
– There is a lot of evidence to support it and no
evidence that rejects it
• Evidence suggests common ancestry
• If two species share a common ancestor, it
follows that the common ancestor changed
(evolved) over time
EVIDENCE OF EVOLUTION
EVIDENCE OF EVOLUTION
#1) Homologous structures:
• Similar bone structures across many
vertebrate species
• suggests a common ancestor
EVIDENCE OF EVOLUTION
EVIDENCE OF EVOLUTION
2) Similarities in Early Development
• Many species have very similar embryonic
development
• Suggests a common ancestor
EVIDENCE OF EVOLUTION
Human and
chimp
chromosomes
EVIDENCE OF EVOLUTION
3) Similarities in DNA & Proteins
• Many species have DNA that is very similar to
other species
• http://ngm.nationalgeographic.com/2013/07/
125-explore/shared-genes
• Indicates the possibility of a common ancestor
EVIDENCE OF EVOLUTION
EVIDENCE OF EVOLUTION
4) Fossils
• Fossils show the changes in organisms over time
• Many species can be traced back to a common
ancestor