Comparative Anatomy

1. EVIDENCE FOR EVOLUTION:
COMPARATIVE ANATOMY
By comparing the anatomy of different animals much
can be learned about their evolution.
HOMOLOGOUS STRUCTURES:
Bones in the forelimb of the human, whale, cat, bat,
bird, alligator are used for vastly different movement,
they all have remarkably similar structure and
organization (bones, nerves, blood vessels
This indicated common ancestry (DNA)
Organs with similar structure but different functions
are called HOMOLOGOUS STRUCTURES

2. COMPARATIVE ANATOMY:
Homologous Structures

3. COMPARATIVE ANATOMY:
Homologous Structures

4. COMPARATIVE ANATOMY:
Homologous Structures

5. COMPARATIVE ANATOMY:
Homologous Structures

6. COMPARATIVE ANATOMY:
Vestigial Structures
•Many animals have structures in their
bodies which seem to be of no use to
them
•These parts are called VESTIGIAL
STRUTURES
•In other species the same structures exist
and they have a definite function

7. COMPARATIVE ANATOMY:
Vestigial Structures
Human Wisdom Teeth ARE Vestigial

8. COMPARATIVE ANATOMY:
Vestigial Structures
•Dogs & humans have
a similar set of
muscles attached to
their ears. The dog
can use these to
“point” its ears in the
direction of a sound,
humans cannot
•In humans the
appendix, coccyx and
hair are all vestigial
structures

9. COMPARATIVE ANATOMY:
Vestigial Structures
TOP 10
VESTIGIAL
SRUCTURES
OF ALL TIME !

10. #10 The Wings on Flightless Birds
In general, wings of a bird are
considered complex structures that
are specifically adapted for flight and
those belonging to these flightless
birds are no different. They are,
anatomically, rudimentary wings, but
they could never give these bulky
birds flight. The wings are not
completely useless, as they are used
for balance during running and in
flagging down the honeys during
courtship displays

12. # 9 Hind Leg Bones in Whales
Biologists believe that for 100 million years
the only vertebrates on Earth were water-
dwelling creatures, with no arms or legs. At
some point these ?fish? began to develop hips
and legs and eventually were able to walk out of
the water, giving the earth its first land lovers.
Once the land-dwelling creatures evolved, there
were some mammals that moved back into the
water. Biologists estimate that this happened
about 50 million years ago, and that this
mammal was the ancestor of the modern whale.
Despite the apparent uselessness, evolution left
traces of hind legs behind, and these vestigial
limbs can still be seen in the modern whale.
There are many cases where whales have been
found with rudimentary hind limbs in the wild,
and have been found in baleen whales,
humpback whales, and in many specimens of
sperm whales. Most of these examples are of
whales that had only leg bones, but there were
some that included feet with complete digits. It
was reported recently that whales and hippos
were distantly related.

13. # 8 Erector Pili and Body Hair
The erector pili are smooth muscle fibers that give
humans’ goose bumps. If the erector pili are activated,
the hairs that come out of the nearby follicles stand up
and give an animal a larger appearance that might
scare off potential enemies and a coat that is thicker
and warmer. Humans, though, don’t have thick furs
like their ancestors did, and our strategy for several
thousand years has been to take the fur off other
warm looking animals to stay warm. It,s ironic actually
that an animal, sensing danger is near, would puff up
its coat to look scarier, but the human hunter would
see the puffier coat as a warm prize, leaving the
thinner haired weaker looking animals alone. Of
course, some body hair is helpful to humans; eye
brows can keep sweat out of the eyes and facial hair
might influence a woman’s choice of sexual partner.
All the rest of that hair, though, is essentially useless.

14. # 7 The Human Tailbone (Coccyx)
These fused vertebrae are the only vestiges
that are left of the tail that other mammals still
use for balance, communication, and in some
primates, as a prehensile limb. As our ancestors
were learning to walk upright, their tail became
useless, and it slowly disappeared. It has been
suggested that the coccyx helps to anchor minor
muscles and may support pelvic organs.
However, there have been many well
documented medical cases where the tailbone
has been surgically removed with little or no
adverse effects. There have been documented
cases of infants born with tails, an extended
version of the tailbone that is composed of extra
vertebrae. There are no adverse health effects
of such a tail, unless perhaps the child was born
in the Dark Ages. In that case, the child and the
mother, now considered witches, would’ve been
killed instantly.

15. # 6 The Blind Fish:
Astyanax Mexicanus
In an experiment designed by nature, the
species of fish known as Astyanax mexicanus,
dwelling in caves deep underground off the
coast of Mexico, cannot see. The pale fish has
eyes, but as it is developing in the egg, the eyes
begin to degenerate, and the fish is born with a
collapsed remnant of an eye covered by flap of
skin. These vestigial eyes probably formed after
hundreds or even thousands of years of living in
total darkness. As for the experiment, a control
is needed; and luckily for us, fish of the same
species live right above, near the surface, where
there is plenty of light, and these fish have fully
functioning eyes. To test if the eyes of the blind
mexicanus could function if given the right
environment, scientists removed the lens from
the eye of the surface-dwelling fish and
implanted it into the eye of the blind fish. It was
observed that within eight days an eye started to
develop beneath the skin, and after two months
the fish had developed a large functioning eye
with a pupil, cornea, and iris. The fish were
blind, but now they see.

16. # 5 Wisdom Teeth in Humans
With all of the pain, time, and money that are
put into dealing with wisdom teeth, humans have
become just a little more than tired of these
remnants from their large jawed ancestors. But
regardless of how much they are despised, the
wisdom teeth remain, and force their way into
mouths regardless of the pain inflicted. There
are two possible reasons why the wisdom teeth
have become vestigial. The first is that the
human jaw has become smaller than its
ancestors? and the wisdom teeth are trying to
grow into a jaw that is much too small. The
second reason may have to do with dental
hygiene. A few thousand years ago, it might be
common for an 18 year old man to have lost
several, probably most, of his teeth, and the
incoming wisdom teeth would prove useful. Now
that humans brush their teeth twice a day, it’s
possible to keep one’s teeth for a lifetime. The
drawback is that the wisdom teeth still want to
come in, and when they do, they usually need to
be extracted to prevent any serious pain.

17. # 4 The Sexual Organs of
Dandelions
Dandelions, like all flowers, have the
proper organs (stamen and pistil) necessary for
sexual reproduction, but do not use them.
Dandelions reproduce without fertilization; they
basically clone themselves, and they are quite
successful at it. Look at any lawn for the proof. If
dandelions were to revert to sexual
reproduction, they might not retain whatever
traits they have that allow them to be pests to
gardeners everywhere. If flowers can begin
reproducing in this manner, does that mean
animals, even humans could too? Asexual
reproduction can be a good strategy in an
environment that is constant if a species is well
suited to those conditions. It doesn’t take a
scientist to figure out that humans wouldn’t last
long if the condition set forth was no sexual
contact with others. Therefore, the human
sexual organs are probably in no danger of
becoming vestigial.

18. # 3 Fake Sex in Lizards
(Vestigial Behavior)
Only females exist in several species of
the lizards of the genus Cnemidophorus,
which might seem like a problem when it
comes time to propagate the species. The
females don’t need the males though, they
reproduce by parthenogenesis, a form of
reproduction in which an unfertilized egg
develops into a new individual. So basically,
the females don’t need the males; they just
produce clones of themselves as a form of
reproduction. Despite the fact that it is
unnecessary and futile to attempt copulation
with each other, the lizards still like to try, and
occasionally one of the females will start to ?
act like a male? by attempting to copulate with
another female. The lizards evolved from a
sexual species and the behavior to copulate
like a male -- to engage in fake sex -- is a
vestigial behavior; that is, a behavior present
in a species, but is expressed in an imperfect
form, which in this case, is useless.

19. # 2 Male Breast Tissue and
Nipples
The subject of male nipples is a
sensitive, and maybe confusing, topic to
many. Those who wish to invalidate
evolutionary theory might pose the question,
?Was man descended from woman?? The
answer, of course, is no. Both men and
women have nipples because in early
stages of fetal development, an unborn child
is effectively sexless. Nipples are present in
both males and females; it is only in a later
stage of fetal development that testosterone
causes sex differentiation in a fetus. All
mammals, male and female, have mammary
glands. Male nipples are vestigial; they may
perform a small role in sexual stimulation
and a small number of men have been able
to lactate. However, they are not fully
functional and, because cancer can grow in
male or female breast tissue, the tissue can
be dangerous.

20. # 1 The Human Appendix
In plant-eating vertebrates, the appendix is
much larger and its main function is to help
digest a largely herbivorous diet. The human
appendix is a small pouch attached to the large
intestine where it joins the small intestine and
does not directly assist digestion. Biologists
believe it is a vestigial organ left behind from a
plant-eating ancestor. Interestingly, it has been
noted by paleontologist Alfred Sherwood Romer
in his text The Vertebrate Body (1949) that the
major importance of the appendix ?would
appear to be financial support of the surgical
profession,? referring to, of course, the large
number of appendectomies performed annually.
In 2000, in fact, there were nearly 300,000
appendectomies performed in the United States,
and 371 deaths from appendicitis. Any
secondary function that the appendix might
perform certainly is not missed in those who had
it removed before it might have ruptured.

21. COMPARATIVE ANATOMY:
Analogous Structures
•Features of different species that are similar in
function but are structurally different
•Do not have a common ancestry
•Evolved due to a similar environmental
challenge
•Ex) Birds & insects have wings to fly although
their wing structure is different
•Ex) Fat insulated, streamlined shapes of seals &
penguins

22. COMPARATIVE ANATOMY:
Analogous Structures

23. COMPARATIVE ANATOMY:
Analogous Structures

26. COMPARATIVE ANATOMY:
Embryology
•Embryological development of all
vertebrates (fish to mammals) is
remarkably similar especially in the early
stages
•The more closely the related organisms,
the longer their embryonic development
proceeds in a parallel fashion

28. COMPARATIVE ANATOMY:
Embryology

29. COMPARATIVE ANATOMY:
Embryology
•Humans have gill pouches in early development
•In fish these pouches develop into gill slits
•In humans they form the eustachian tube and
auditory canal, which except for the eardrum,
are a direct connection between the outside of
the body and the pharynx
•Human embryo has a tail and body hair like
embryos of all other mammals but in the human
embryo these features disappear before birth
•The presence of these features provides
evidence that humans & other mammals
developed from common ancestors

30. COMPARATIVE ANATOMY:
Embryology

31. COMPARATIVE BIOCHEMISTRY
•In studying the complex molecules making
up the bodies if living things, we find
incredible similarities in the structures of
these molecules in various organisms.
•Closely related species are very similar at
the molecular level
•Distantly related species are more
dissimilar at the molecular level but
similarities still exits

32. COMPARATIVE BIOCHEMISTRY
1. All cells are made up
of the same basic types
of organic compounds:
nucleic acids, lipids,
carbohydrates

33. COMPARATIVE BIOCHEMISTRY
2.In all organisms, reactions involving these
organic compounds are controlled by
proteins known as enzymes

34. COMPARATIVE BIOCHEMISTRY
3. In all cells,
proteins are
synthesized
from about 20
known amino
acids

35. COMPARATIVE BIOCHEMISTRY
4.Carbohydrate
molecules of cells
consist of 6 carbon
sugars (glucose) and
polymers of these
(cellulose, starch,
glycogen)

36. COMPARATIVE BIOCHEMISTRY
5.All cells obtain energy
from processing
glucose in glycolysis
In most organisms,
oxygen can be used as
an electron acceptor in
the breakdown of
pyruvic acid to CO2 and
water

37. COMPARATIVE BIOCHEMISTRY
6.All cells contain DNA,
a molecule that carries
coded information
controlling the
metabolism of the cell.
DNA also transmits
the coded information to
new cells

38. COMARATIVE BIOCHEMISTRY
7. DNA in organisms
determines the
specificity of proteins
through intermediate
compounds such as
mRNA

39. COMPARATIVE BIOCHEMISTRY
8. Structures of
important lipids,
proteins, & specialized
molecules such as
DNA, RNA, ATP and
some co-enzymes are
similar

40. COMPARATIVE BIOCHEMISTRY
The Genetic
Code is
Universal

41. AGE OF THE EARTH

42. AGE OF THE EARTH

43. AGE OF THE EARTH
•Lord William Thomson Kelvin was the 1
st
to try to determine the age
of the Earth
•In 1866 he assigned it an absolute age of 400 million years (later
revised his estimate to 15-20 millions yrs.
•Pierre Currie (1903) discovers radioactive decay. Its use provided
geologists with the means to estimate the absolute age of the Earth
•Radiometric dating has been used to date meteorite samples. All
that have struck Earth have been about 4.6 billion yrs
•Moon rocks from the Apollo missions have been dated at 4.53 billion
yrs
•Oldest rock on Earth (from Canadian Shield) is 3.9 billion yrs old.
This is the age where the Earth began to cool & did not undergo
further melting. The Earth is likely 4.6 billion years old.

44. GEOGRAPHIC DISTRIBUTION
Inhabitants of ocean islands
resemble forms of the nearest
mainland but show some
differences, which suggests that
they have evolved from mainland
migrants
Green Iguana from Panama
Galapagos Land Iguana

45. PROTECTIVE RESEMBLENCE:
Industrial Melanism
•Shows the effects of
an environmental
change on selection
patterns of birds that
eat peppered moths
•Industrial melanism is
a phrase to describe
the evolutionary
process in which light
colored moths
become dark as a
result of natural
selection

46. DOMESTICATION & ARTIFICIAL SELECTION
•We can easily breed
animals/plants to
achieve desirable
characteristics
•If we can achieve
these changes over a
a short period of time,
the environment could
cause changes in a
long period of time