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Evolution
Lamarck’s Theory of Acquired Inheritance
(early 1800s)
• Jean Baptiste Lamarck
• Observed fossil records and
the current diversity of life
• Suggested that organisms
evolved by the process of
adaptation
• Traits gained during a
lifetime could then be passed
on to the next generation
Charles Darwin
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 that 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
Artificial selection
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
Evidence of Evolution
•
•
•
•
•
Fossil Record
Biogeography
Comparative anatomy
Comparative embryology
Molecular Biology
Evidence: Fossil Record
• Fossils
– preserved remnants or
impressions left by
organisms that lived in
the past.
– often found in
sedimentary rocks.
http://www.buzzle.com/img/articleImages/191116-18med.jpg
Fossil Formation
1.
Dead animal sinks. Tissue
begins to decay
2.
Carcass covered with sediment.
Lower layers turn to rock.
3.
Rock is folded.
4.
Fossil is exposed at the surface.
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The fossil record
• Is the ordered sequence of fossils as they
appear in rock layers.
• Reveals the appearance of organisms in a
historical sequence.
• Fits with other evidence of evolution.
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The fossil record
Generally less
complex forms of
life are found in
oldest rocks.
http://www.biblicalcreation.org.uk/images/Matthew_Fig.jpg
Evidence: Biogeography
• The geographic distribution of species
• Darwin noted that Galápagos animals
– Resembled species of the South American
mainland more than animals on similar but
distant islands
Evidence: Comparative
Anatomy
• Comparison of body structures between
different species
– Similarities give signs of common
descent/common ancestor
• Homologous structures—features that
have similar structure but may have
different functions
Evidence: Comparative Anatomy
•
Vestigial structures—Small body structures
that may have been functional in the ancestors
of a species, but have no or limited function at
the present time
vestigial structures
Evidence: Comparative embryology
• Different organisms go through similar embryonic stages
• All vertebrates have an embryonic stage in which gill
pouches and post-anal tail—evidence of a common
ancestor
Molecular Biology
• Study of molecular basis of genes
• Universality of genetic code
• Conservation of amino acid sequences in
proteins such as hemoglobin/cytochrome C
Figure 13.13
For each example below, identify the type of evidence of evolution
1.
2.
Cats and humans both have muscles for moving their ears
3.The start codon places
methionine at the first amino
acid position for virtually all
proteins
4. Over the past 47 million years
the location of the nostrils are
seen to have shifted posteriorly in
relatives to the modern day
dolphin
Generation to generation change in the
frequencies of alleles in the gene
Causes:
Natural selection
Genetic drift
Gene flow
Mutation
pool
Natural selection
Genetic Drift: changes in allele frequencies due
to chance
Ex #1: Natural disaster wipes out a portion of a population
Fig. 13-11a-3
Original
population
Bottlenecking
event
Surviving
population
Example #2
Relatively few
individuals start a new
population in isolation
founder effect
Gene flow immigration or emigration of
individuals (and their genes)
Population A
Population B
Mutation introduces new alleles
A population that is not evolving is in equilibrium
Hardy-Weinberg Equilibrium mathematically
describes these populations
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
There are 100 students in a class. Ninety-six did well in the course whereas
four blew it totally and received a grade of E. In the highly unlikely event that
these traits are genetic rather than environmental, if these traits involve
dominant and recessive alleles, and if the four (4%) represent the frequency
of the homozygous recessive condition, calculate the following:
The frequency of the recessive allele.
The frequency of the dominant allele.
The frequency of heterozygous individuals.
Within a population of butterflies, the color brown (B) is dominant over the
color white (b). And, 40% of all butterflies are white. Given this informationm
calculate the following:
The percentage of butterflies in the population that are heterozygous.
The frequency of homozygous dominant individuals.
You have sampled a population in which you know that the
percentage of the homozygous recessive genotype (aa) is 36%.
Using that 36%, calculate the following:
The frequency of the "aa" genotype.
The frequency of the "a" allele.
The frequency of the "A" allele.
The frequencies of the genotypes "AA" and "Aa."
Comparative Anatomy
Anatomical
Homologous
structures:
indicators of a
common ancestor
Show divergent
evolution
A) Divergent evolution  results in
homologous structures
B) Convergent evolution  results in
analogous structures
Analogous structures
Evolved independently and don’t indicate close
relationships
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. 14-3a
Habitat isolation
Fig. 14-3b
Behavioral Isolation
Behavioral Isolation
Fig. 14-3c
Mechanical Isolation
Fig. 14-3d
Gametic Isolation
Fig. 14-3e
National Geographic
http://www.youtube.com/watch?
v=1zOWYj59BXI
Speciation
Formation of new species
-sometimes from geographic isolation
• Speciation without geographic isolation
• Polyploidy occurs in plants
3
2
Selffertilization
Parent species
2n = 6
Tetraploid
cells
4n = 12
Diploid
gametes
2n = 6
Viable, fertile
tetraploid
species
4n = 12
Formation of hybrid that reproduces asexually and later
(through errors in cell divisions) becomes fertile is common in
plants
Chromosomes not
homologous
(cannot pair)
1
Species A
2n = 4
2
3
Gamete
n=2
Sterile hybrid
n=5
Species B
2n = 6
Gamete
n=3
Viable, fertile
hybrid species
2n = 10
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
feathers
• Beastie Activity
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
EARLY LIFE
– Earth formed 4.6 billion years ago
– Oldest fossils are 3.5 billion
years old
• Photosynthetic bacteria in
stromatolites
– Heterotroph hypothesis
– first living things (heterotrophs)
are thought to be simpler and arose much earlier
– Heterotrophs have much simpler metabolism, occurred before
autotrophs
Copyright © 2009 Pearson Education, Inc.
Possible evolution of chemicals
that could result in first cells
Chemical conditions
Physical conditions
Stage 1
Abiotic synthesis
of monomers
Stage 2
Formation of polymers
Stage 3
Stage 4
Copyright © 2009 Pearson Education, Inc.
Packaging of polymers
into protobionts
Self-replication
• Possible composition of Earth’s early atmosphere
–
–
–
–
H2O vapor
N2
CO2, CH4, NH3,
H2, and H2S
• Energy sources
– Lightning, volcanoes,
UV radiation
Stage 1: Abiotic synthesis of monomers
– Organic molecules were produced in the lab using
molecules and energy sources thought to be on
primitive earth
Copyright © 2009 Pearson Education, Inc.
• Stage 2: The formation of polymers
– Monomers could have combined to form organic
polymers
– Same energy sources
Copyright © 2009 Pearson Education, Inc.
• Stage 3: Packaging of polymers into
protobionts
– Polymers could have aggregated into complex,
organized, cell-like structures
Copyright © 2009 Pearson Education, Inc.
– Stage 4: Self-replication
– RNA may have served both as the first genetic material
and as the first enzymes
2 Assembly of a
Monomers
1 Formation of short RNA
polymers: simple “genes”
protocells
complementary RNA
chain, the first step in
replication of the
original “gene”
First organisms were prokaryotic
eukaryotic organisms evolved later
5 KINGDOMS
1) MONERA
2) PROTISTA
3) FUNGI
4) PLANTAE
5) ANIMALIA
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