Transcript Evolution: Natural Selection & Adaptation

Chapters 15 and 16
I.
Evolution is the Unifying Principle of all Biology
A.
forms foundation for all other concepts
1.
2.
B.
two major aspects:
1.
2.
II.
answers all “why” questions
explains context of boil. phenomena
descent from a common ancestor  why org. have similar characteristics
adaptation to environment  explains diversity of life
Charles Darwin
A.
developed theory of evolution
•
B.
1859: The Origin of Species
descent with modification
•
C.
“change through time”
evol. occurs through natural selection
1.
env. determines which ind. will survive and reproduce
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are fittest ind.  possess best adaptations
2.
adaptations
•
characteristics that increase chance of survival and reproduction
III. Natural Selection
A.
B.
mechanism of evol.
based on five key points:
1.
2.
3.
4.
5.
C.
ind. vary within pops.
some variation is inherited and affects survival
more offspring are produced than env. can support
offspring with most adaptive traits will survive
and produce more of their own offspring
•
offspring will also have the adaptive traits
over time, the pop. changes
•
more adaptive traits become more prevalent
better
environmental forces affect an individual’s phenotype
1.
2.
3.
4.
to survive, an org’s. phenotype must become adapted to env.
•
but, genotype determines phenotype
orgs. with most adaptive genotypes survive better and pass their genes
onto their offspring
•
their genotypes produce a more fit and adaptive phenotype
o
such organisms are “selected for”
variation in pop.  small genetic changes  produce new genotypes 
lead to new, better adapted phenotypes
continued phenotypic change  development of new species
D.
variation
1.
2.
occurs in pops. in many different traits
a. behavioral, biochemical, physical
b. must be genetically based
c. two primary sources
i.
mutation
•
source of new variations
ii. crossing over
•
source of new combinations of traits
d. is very beneficial to a pop.  evol. cannot occur without it
maintained through a wide variety of mechanisms
a. dispersal of young
b. masking recessive alleles
c. heterozygote advantage
d. others
Fig. 15.7 Variation in
a human population
Fig. 16.16
An example of heterozygote advantage
E.
Modern Synthesis – Today’s Theory of Evolution
•
F.
G.
H.
nat. sel. causes populations to change, not individuals
selection is not a random process
evol. is not based on the needs of organisms
•
I.
J.
incorporates genetics into evolution
mutations  acted on by nat. sel.  adaptation to local env. conditions
selection has been tested and confirmed many times in many organisms
fittest ind. are those more likely to survive, based on adaptations
1.
2.
evolution is not “survival of the fittest”
survival not as important as reproduction
Fig. 16.3
Natural
selection in
peppered
moths
IV. Evidence and Examples of Evolution
A. fossil record
1. radioactive dating
2. hard-bodied vs. soft-bodied organisms
3. phylogenetic trees
Fig. 17.17
Evolutionary
history of
Equus
Fig. 30.7
Human evolution
B. biogeography
1.
2.
3.
4.
study of where organisms are found on earth
provides evidence of past evol. history
isolated regions have their own types of plants and animals
similarity of unrelated species in similar environments
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Biogeographical regions
Fig. 15.5 An example of
evidence through biogeography
– the European hare and the
Patagonian (S.A.) hare
Fig. 15.14 Biogeography. Some mammals of Australia and their North
and South American counterparts.
C.
comparative anatomy
1.
2.
3.
4.
homologous vs. analogous structures
adult and embryological evidence
transitional organisms
vestigial structures
Fig. 15.16
Fig. 15.15
Homologous structures
Developmental homologies
Fig. 15.13 Ambulocetus – an ancestor of
whales and a transitional fossil
Fig. 15.12 Transitional fossils - Archaeopteryx
Some vestigial
structures
Fig. 17.1 Whale evolution,
showing transitional organisms
D. molecular biology
1.
2.
3.
4.
genetic code and cellular structure
DNA and amino acid similarities
number of mutations
phylogenetic trees
Fig. 15.17 Biochemical differences – evidence from molecular biology
E. artificial selection
• selective breeding
Fig. 15.9
Fig. 15.8 Artificial selection in animals
Artificial selection in plants