Transcript Homologous Structures

DO Now
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What is Evolution?
What is genetic variation?
What is struggle of the fittest?
What is natural selection?
How do animals evolve: use genetic variation,
struggle of the fittest and natural selection in
your answer.
Wednesday, November 20, 2013
Your Learning Goal: Students will be able to
defend the theory of evolution using
homologous structures as their evidence.
Standard 3c:Students know independent lines of
evidence from geology, fossils, and
comparative anatomy provide the bases for the
theory of evolution
Table of Contents: 3.10 Evolution Defense
Homework:
Homologous structures
as evidence for
evolution
Agenda:
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4.
Do-Now
Homologous notes
Are these animals
homologous
Work on HW
Why do you think birds and bats both
have wings?
Why do you think birds, reptiles,
amphibians, and mammals all have
lungs? (fish don’t)
Comparative Anatomy
Comparative Anatomy
• Comparative anatomy looks at the similarities
and differences in the anatomy of organisms,
and how these structures are used.
– The anatomy is the way the body is designed:
bone structure and organ structures.
– Comparing the way organisms are put together
Homologous structures
• Homologous Structures- Body structured that are
similar in different species because the species have
common descent. The structure was evolved from a
shared ancestor
– Common Descent: They evolved from the same ancestor
• The structures may or may not perform the same
function.
• Homologous structures provide evidence of evolution
because these structures are too similar to be
coincidence and have been adapted for the different
environments of the different animals.
Vertebrate Limbs & Common Ancestor
Which limb is not homologous? Why?
Human
A
Octopus
Lizard
Human
B
Lizard
Bird
Whale
Grasshopper
Comparative Anatomy: Homologous
structures
• For example: same bone structure found in a human
arm, bat wing, whale flipper, and cat leg…
• The gene to signal the formation of eyes is
homologous for humans and insects. What do
you think will happen if you replace the insect
eye gene with the human eye gene?
• The eye gene to create eyes is homologous, it
was evolved by a common ancestor. If you
switch the human eye gene for the insect eye
gene the insect will still grow an eye.
Can Genes be Homologous?
Vestigial Structures
• Vestigial Structures: Homologous structures
present in an organism that has lost its function.
– These structures don’t do what they were originally
evolved to do
• Evidence of evolution because animals had them
and evolved to not use them
• Examples:
– Whales have leg bones buried in the back of their
bodies
– Human appendix is vestigial to an organ used to digest
cellulose in primitive ancestor
Theory of Whale evolution:
Other vestigial Examples
• Wings on flightless birds
• Human tail bone
• Wisdom teeth in humans
Analogous Structures
• Analogous structures: structures that have
similar look and/or functions in different
species, but do not share a common descent
– The two structures evolved separately and are
unrelated
• For example:
• Wings of insects vs. wings of birds vs. Bats
Why do you think animals evolve
analogous structures separately
Why do you think animals evolve
analogous structures separately
• The environments could have similar qualities
with similar struggles. In both environments,
the similar analogous structure was the best
and naturally selected to become adaptations.
1. Are all of these different leaves Homologous?
2. Wings of a bat and a robin?
Fish
Amphibians
Reptile
Mammals
Bird
And
scales!
3. Scales on a brown trout and a lizard?
Fish
Amphibians
Reptile
Mammals
Bird
And
scales!
4. Front teeth on a beaver and the tusks on an elephant?
5. Wings of a dragon fly and the wings of a butterfly?
6. The limbs of an eagle and the limbs of a penguin?
7. Fins of a shark and the fins of a dolphin?
Fish
Amphibians
Reptile
Mammals
Bird
And
scales!
8. No limbs on a water snake or an eel?
Fish
Amphibians
Reptile
Mammals
Bird
And
scales!
9. Opposable thumbs of the bush baby and the human?
10. Gliding adaptation of the marsupial sugar glider from
Australia and the placental gliding squirrel of the Americas?
Answers
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Yes
No
No
Yes
Yes
Yes
No
No
Yes
No
What do you call the structures that
were similar that were not
homologous
• What’s the difference between the
homologous and analogous structures?
• Homologous structures evolved from a
common ancestor. The two different species
received the structure from the same
ancestor. Analogous structures evolved
separately because of natural selection. The
structures are unrelated.
Evolution of the bird
• The bird evolved from 4 legged dinosaurs that
walked on their hind legs. One of the
ancestors include the velociraptor
• Are birds more related to the pterodactyl, a
flying dinosaur, or the velociraptor, a dinosaur
that could not fly? And why?
• Birds are more related to the velociraptor
because birds evolved from velociraptors and
did not evolve from pterodactyls. The wings
of a pterodactyl and a bird are analogous.
They were separately naturally selected.
Claim
Evolution exists
Evidence 1: Homologous structures:
What are homologous structures?
Evidence 2: Vestigial structures:
What are vestigial structures?
Evidence 3: Analogous structures:
What are analogous structures?
Reasoning 1: How do homologous structures
prove evolution?
Reasoning 2: How do vestigial structures prove
evolution?
Reasoning 1: How do analogous structures
prove evolution
Claim
Evolution exists
Evidence 1: Homologous structures:
What are homologous structures?
Evidence 2: Vestigial structures:
What are vestigial structures?
Evidence 3: Analogous structures:
What are analogous structures?
Reasoning 1: How do homologous structures
prove evolution?
Reasoning 2: How do vestigial structures prove
evolution?
Reasoning 1: How do analogous structures
prove evolution