Transcript Homologous structures

How did the giraffe get its long neck?
Observation #1
More offspring are
produced that can possibly
survive.
BUT populations tend to
remain stable
AND there are
limited resources
SO the inference is:
There is a struggle for survival between
individuals of a population and not all will survive
Aphaenogaster tipuna ants fighting over food
OBSERVATION #2
Organisms display
a lot of variety in
their characteristics
Much of this
variety is inherited
Inference #2:
Those individuals whose inherited
traits best fit them to their
particular environment will leave
more offspring
Inference #3:
This unequal ability of individuals to
survive and reproduce will cause a
gradual change in the population
Favorable characteristics will
accumulate in the population over
time
Individuals DO NOT EVOLVE. Populations evolve
Evolution is not caused by a NEED of an individual.
Surviving does not contribute to evolution alone.
There also has to be reproduction
Acquired characteristics are not passed down to the
next generation.
Adaptations depend on the environment
Fossils provide evidence
of the change of life
throughout time
Comparative Anatomy
Anatomical
Homologous
structures:
indicators of a
common ancestor
Show divergent
evolution
vestigial structures
Homologous
structures with no
or little function in
organism
Embryological homologies
Compare DNA
sequences or proteins
(amino acid
sequences)
The more differences the
longer ago the two species
diverged from a common
ancestor
Generation to generation change in the
frequencies of alleles in the gene
pool
Causes:
natural selection
Genetic Drift: changes in allele frequencies due
to chance
Gene flow immigration or emigration of
individuals (and their genes)
Mutation introduces new alleles
Examples of Genetic Drift
Bottleneck effect
Natural disaster wipes out a portion of
a population
Fig. 13-11a-1
Original
population
Fig. 13-11a-2
Original
population
Bottlenecking
event
Fig. 13-11a-3
Original
population
Bottlenecking
event
Surviving
population
Example #2
Relatively few individuals start a new
population in isolation
founder effect
A population that is not evolving is in equilibrium
Hardy-Weinberg Equilibrium
p=frequency of the dominant allele
q=frequency of the recessive allele
p+q=1
p2 +2pq +q2=1
p2 = frequency of homozygous dominants
2pq= frequency of heterozygotes
q2= frequency of homozygous recessives
Conditions required for a population to
maintain Hardy-Weinberg equilibrium
1.
2.
3.
4.
5.
Large population
Random mating
No natural selection
No mutation
No gene flow
Analogous structures
Evolved independently
and don’t indicate close
relationships
A) Divergent evolution  results in
homologous structures
B) Convergent evolution  results in
analogous structures
Population or group of populations that have
the potential to interbreed with each other in
nature and produce viable offspring
Key idea: reproductive isolation
Fig. 14-3
Fig. 14-3a
Habitat isolation
Fig. 14-3b
Behavioral Isolation
Behavioral Isolation
Fig. 14-3c
Mechanical Isolation
Fig. 14-3d
Gametic Isolation
Fig. 14-3e
Postzygotic Barriers
Hybrids do not develop into fertile
adults
National Geographic
http://www.youtube.com/watch?
v=1zOWYj59BXI
Speciation is the formation of a new
species
Often it comes about because of
some kind of geographic
barrier
Adaptive radiation is a type of speciation
One population evolves into several different
species, each with different adaptive
characteristics
Phylogenetic trees
Cactus
ground finch
Medium
ground finch
Large
ground finch
Small
Large cactus
ground finch ground finch
Sharp-beaked
ground finch
Seed
eaters
Cactus flower
eaters
Ground finches
Is the medium ground finch more
closely related to the small ground
finch or to the large ground finch?
Small
tree finch
Vegetarian
finch
Medium
tree finch
Large
tree finch
Bud
eaters
Woodpecker
finch
Mangrove
finch
Green
warbler finch
Insect
eaters
Tree finches
Warbler finches
Which finch is most
closely related t the
Green warbler finch?
Loss of tail
3 toes
Big eyes
• Beastie Activity
Duck-billed
platypus
Kangaroo
Beaver
TAXA
Iguana
CHARACTERS
Fig. 15-16aa
Long
gestation
0
0
0
1
Gestation
0
0
1
1
Hair, mammary
glands
0
1
1
1
Character Table
Fig. 15-16ab
Iguana
Duck-billed
platypus
Hair, mammary glands
Kangaroo
Gestation
Beaver
Long gestation
Phylogenetic Tree
Loss of tail
3 toes
Big eyes
Brown bear
Polar
bear
Asiatic
black
bear
American
black
bear
Sun
bear
Sloth
bear
Spectacled Giant
panda
bear
Lesser
Raccoon panda
Miocene
Pleistocene
Pliocene
Oligocene
Ursidae
Procyonidae
Common ancestral
carnivorans
Figure 15.12A
Classification
• For several decades, scientists have classified life
into five kingdoms
MONERA
PROTISTA
PLANTAE
Earliest
organisms
FUNGI
ANIMALIA
Figure 15.14A
A newer system is the 3 Domain system
• This system recognizes two basically distinctive
groups of prokaryotes
– The domain Bacteria
– The domain Archaea
• A third domain,
the Eukarya,
includes all
kingdoms of
eukaryotes
BACTERIA
ARCHAEA
EUKARYA
Earliest
organisms
Figure 15.14B
• Organisms are grouped into progressively larger
categories (taxons)
Table 15.10
CLASSIFICATION
(TAXONOMY)
DOMAIN
KINGDOM
PHYLUM
CLASS
ORDER
FAMILY
GENUS
SPECIES (SMALLEST GROUP)
NAMING OF ORGANISMS
BINOMIAL NOMENCLATURE
EX: Homo sapiens
Pan troglodytes (chimpanzee)
FIRST NAME IS GENUS NAME
SECOND NAME IS SPECIES NAME
5 KINGDOMS
1) MONERA
2) PROTISTA
3) FUNGI
4) PLANTAE
5) ANIMALIA
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