Transcript Why is life on Earth so diverse???

More Historical
Evidence
The study of Homologies
Homology
► What
does the word Homologous mean?
► Homology is the study of similarity between
organisms
► There are three major branches of
homology:
 Anatomical Homology
 Embryological Homology
 Molecular Homology
Anatomical Homology
► Outwardly,
these look
like very different
structures.
Beneath The Surface…
Strange Coincidence?
► At
a structural level, the wing of a bat, a human
arm and a whale’s flipper all share the same
number, type and location of bones, suggesting
that THEY MAY SHARE COMMON ANCESTRY
► 'What
can be more curious than that the hand of a
man, formed for grasping, that of a mole for
digging, the leg of the horse, the paddle of the
porpoise, and the wing of the bat should all be
constructed on the same pattern and should
include similar bones in the same relative
position?' (Charles Darwin)
Vestigial Structures
► Some
organisms have structures that appear to be
useless relics of the past
► Suggests that these organisms may be descended
from ancestral organisms in which the structure IS
still useful!
Evidence of Evoluton
► Analogous
Structures: structures similar in
function, but not inherited from a common
ancestor.
► Same function, different structure
Embryological Homology
►
The diagram below shows embryos of
five different species: pig, chicken, fish,
turtle, and human. Can you tell which is
which?
Figured it out yet?
How about now?
Did you guess correctly?
Embryological Homology
►
►
Did you know that when you were inside your mother’s
womb, for a while you looked almost exactly like a fish?
Vertebrate embryos all share a similar pattern of
development, suggesting that they may share common
ancestry
Chicken – 2 ½ days
Human – 31 days
Pig – 21 days
Molecular Homology
► All
living things contain DNA and RNA.
► Changes
in Proteins, DNA and RNA can be
traced from ancestors to their descendents.
► The
fewer Amino Acid differences between
organisms, the closer their inferred
evolutionary relationship.
 Hemoglobin and Cytochrome C are a group of
proteins that are commonly found in many
different organisms
Proteins & Amino Acids
Apple
Protein
► Proteins
Celery
Protein
(eg. Hemoglobin, Cytochrome c) can
exist in subtly different forms, depending on
their specific Amino Acid configuration
Our Chimpanzee “Cousins”?
► Comparison
of
chimp and human
chromosomes
reveals many
similarities
► Could we be related
by common
descent?...
Example: the Evolutionary
Hypothesis of Common
Ancestry
Chromosome Numbers in
the great apes:
human (Homo)
chimpanzee (Pan)
gorilla (Gorilla)
orangutan (Pogo)
46
48
48
48
Testable prediction: If these
organisms share common ancestry,
the human genome must contain a
fused chromosome.
Comparing Chromosomes
The banding patterns on
stained chromosomes
show regions of tightly
condensed (dark) and
loosely condensed (pale)
Histone proteins
► Protein location is
dependent on gene loci,
and the bands can
therefore be used to infer
genetic similarity
► How similar would you
expect our banding
pattern to be, compared
to Chimpanzees?
►
Human vs.
Chimp
Chromosomes
• Human chrom. are
on the left
• Chimp’s are on the
right
• Notice that Human
Chromosome #2
appears to be a
combination of
Chimp Chromosomes
#2 & 3
Ancestral
Chromosomes
Chromosome Numbers in
the great apes
(Hominidae):
human (Homo)
chimpanzee (Pan)
gorilla (Gorilla)
orangutan (Pogo)
Fusion
Homo sapiens
Centromere #1
46
48
48
48
Telomere
sequences
Centromere #2
Centromere
Telomere
Testable prediction: The marks of that fusion
must appear in one of the human
chromosomes.
Human Chromosome #2 shows the
exact point at which this fusion
appears to have taken place
Homo sapiens
Inactivated
centromere
Telomere
sequences
“Chromosome 2 is unique to the human lineage of
evolution, having emerged as a result of head-tohead fusion of two acrocentric chromosomes that
remained separate in other primates. The precise
fusion site has been located in 2q13–2q14.1 (ref.
2; hg 16:114455823 – 114455838), where our
analysis confirmed the presence of multiple
subtelomeric duplications to chromosomes 1, 5, 8,
9, 10, 12, 19, 21 and 22 (Fig. 3; Supplementary
Fig. 3a, region A). During the formation of human
chromosome 2, one of the two centromeres
became inactivated (2q21, which corresponds to
the centromere from chimp chromosome 13) and
the centromeric structure quickly deterioriated
(42).”
Hillier et al (2005) “Generation and Annotation of the DNA sequences of human
chromosomes 2 and 4,” Nature 434: 724 – 731.
What do YOU think about this information…?
What do you think…?
Darwin had NO IDEA about Chromosomes – does this new information
SUPPORT his evolutionary hypothesis, or NOT…?
Present-Day Evidence
For Evolution
“Observing Evolution In Action”
Natural Selection
► Is
there any evidence of Natural Selection
taking place in real populations?
► One study, performed during the industrial
revolution in England, demonstrated that
populations of organisms ARE greatly
affected by environmental changes
The Peppered Moth
►
►
►
Two different forms of the moth existed
One Dark form, one Light
Both forms were common
Antibiotic Resistance
► Because
Bacteria reproduce so quickly, they
represent excellent specimens for testing
Natural Selection
► Watch how quickly they can “evolve”
because of Natural Selection…
Examples of Evolution at Work
Speciation (formation of a new species)
► results
from reproductive isolation - when
members of two ancestral populations can no
longer interbreed to produce fertile offspring
► How do populations get isolated?....
Isolating Mechanisms
Behavioral Isolation
Two populations are capable of
interbreeding but have
differences in courtship rituals.
Both birds are in the
same geographic range but
they have a different
mating song
Eastern Meadowlark
Western Meadowlark
Isolating Mechanisms
Geographic Isolation
Two populations separated by
geographic barriers like rivers,
and mountains
Colorado river separated
this species into two
separate populations. A
new subspecies formed –
the Kaibab squirrel
Abert squirrel
Kaibab squirrel
Isolating Mechanisms
Temporal Isolation
Individual varieties of an
organism may breed at different
times of day/year
Ex. Orchids in a rainforest