Transcript Analogous structure

Comparative Anatomy

Scientists can
compare the
anatomy of
different organisms
to figure out how
closely they are
related.
Anatomy
structure
= body
Homologous Structures





Similar in Origin
Different in Function (bird wing/human arm)
Recent common ancestor
May appear in embryonic development and
disappear before birth.
Key Point #1: Homologous features are those that
have similar structure but different functions.
Homologous Structures=recent
common ancestor!!
Analogous Structures


Analogous structure: Parts of different species that have
the same function, but EVOLVED SEPARATELY
Key Point #2: Analogous structures show that unrelated*
species will evolve similar adaptations in response to
similar environmental pressures


Natural selection selects for (keeps around) mutations that
increase fitness in the specific environment.
If organisms they live in similar environments, they will evolve
similar structures.
Insect, bird, and bat wings evolved completely separately.
Unrelated organisms will evolve similar adaptations in
response to similar environmental pressures!
No recent common ancestor!!!
Seals and penguins both have streamlined bodies, and store
fat to keep them warm in the cold water. Unrelated
organisms will evolve similar adaptations in response to
similar environmental pressures!
Vestigial Structures
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Vestigial structure: Part of an organism that is no
longer used for anything
Key Point #3: Vestigial structures show that a
species used to live in a different environment.
Organism moved into a new environment, where the
vestigial structure decreases fitness
No longer needed, waste of energy
 Risk of disease

Letter “c” = hind legs of a baleen whale skeleton
Vestigial = no longer used!!!
Blind salamanders have eye sockets!?!?
So, what about me?
Guided Practice – Notes Reflection

How do analogous structures provide evidence for
evolution?
 Analogous
structures show that unrelated* organisms
will evolve similar adaptations in response to similar
environmental pressures
If you can’t find the answer…
ADD IT!!!
Guided Practice – Notes Reflection

How do vestigial structures provide evidence for
evolution?
 Vestigial
structures show that the species used to live in
a different environment
 Organism moved into a new environment where the
vestigial structure decreased fitness… so it started to
degrade
If you can’t find the answer…
ADD IT!!!
Guided Practice (GP)
Are these structures…
(A) Homologous, (B) Vestigial, (C) Analogous?

Human embryos and cat embryos both have gill
slits.
HOMOLOGOUS
Guided Practice (GP)
Are these structures…
(A) Homologous, (B) Vestigial, (C) Analogous?

Birds and insects both have wings, but they
developed in completely different ways.
ANALOGOUS
Guided Practice (GP)
Is this structure…
(A) Homologous, (B) Vestigial, (C) Analogous?

Snakes don’t have legs, but they do have hip and
leg bones.
VESTIGIAL
Guided Practice (GP)
Is this structure…
(A) Homologous, (B) Vestigial, (C) Analogous?

The human appendix – a small organ next to the
intestines – doesn’t seem to do anything at all.
VESTIGIAL
Guided Practice (GP)
Are these structures…
(A) Homologous, (B) Vestigial, (C) Analogous?

Cat embryos and human embryos both have tails.
HOMOLOGOUS
Guided Practice (GP)
Are these structures…
(A) Homologous, (B) Vestigial, (C) Analogous?

Dolphins and sharks both have fins, but they
evolved completely differently.
ANALOGOUS
Guided Practice (GP)
Are these structures…
(A) Homologous, (B) Vestigial, (C) Analogous?

Alligators and bats have the same bone structure in
their forelimbs (front legs for alligators, wings for
bats).
HOMOLOGOUS
Guided Practice (GP)
Is this structure…
(A) Homologous, (B) Vestigial, (C) Analogous?

Humans have wisdom teeth (third molars), even
though they are not needed to chew up food.
VESTIGIAL
Guided Practice (GP)
Are these structures…
(A) Homologous, (B) Vestigial, (C) Analogous?

Humans and squids both have eyes, but they
evolved in completely different ways.
ANALOGOUS
Embryo

An early stage in the development of an organism
 Often
embryo’s have structures that are not present after
the organism is born
Human Embryo
Cat Embryo
All the above have folds called gill pouches
in the neck region. All similar by the fact
they are all vertebrates.
Embryology
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The study of embryos.
The chemical make-up of organisms also provides
clues to common ancestry.
 Example:
Scientist compare the sequences of the
nucleotides in DNA and the amino acids making up
certain proteins in different organisms. The more
similarities found in 2 DNA or amino acid sequences,
the more closely related the organisms are.
 Example:
Hemoglobin blood in chimpanzee’s is more similar
to human hemoglobin than a cats hemoglobin is to a human.
( Chimpanzees and humans are more closely related)
Exit Question: Choose one option
A
All humans have a tail bone,
but we don’t have tails.
 What type of structure is
this?
 EXPLAIN how this
structure provides
evidence for evolution.
B
Write in complete sentences!
Dogs and alligators both
have long snouts that
allow their jaws to open
wide. However, they
evolved in completely
different ways.
 What type of structure is
this?
 EXPLAIN how these
structures provide
evidence for evolution.