EVOLUTION
(Two Lectures)
I.
INTRODUCTION
A. Observations
1.
All life forms share certain common characteristics (unity)
2.
There are many forms of life on earth today (diversity)
B.
Explanation: Principle of Evolution
1.
Unity: common descent
2.
Diversity: adapt to environment (Natural Selection)
3.
Define: Hypothesis  Theory Principle: Scientific Method
observations  hypothesis  scientific (controlled) observations/experiments 
interpretation of new data  conclusion  reject/support hypothesis
Many scientific observations/experiments over long time period = THEORY
Theories that are generally accepted as valid by an overwhelming # of scientists =
PRINCIPLE / LAW
II.
III.
CHARLES DARWIN
A. 1831 - MHS Beagle naturalist (see p 241 map)
B.
1858 - Darwin & Wallace both proposed natural selection. Data to back
theory: Origin of Species
C.
Other hypotheses for agents of evolutionary change rejected by physical
evidence: Ex: Lamarck: Inheritance of acquired characteristics
1.
If you don't use it, you loose it
2.
No scientific evidence to support
Ex: muscles atrophy in individual; offspring have potential muscle
development
POPULATION GENETICS (MICROEVOLUTION)
Changes in a population's allele frequencies over time.
A.
Definitions:
1.
Population = all members of single species occupying a particular
area at the same time.
2.
Species = interbreed & produce viable offspring
3.
Allele = version of a gene. It shows one particular manifestation of
a trait.
4.
Gene = section of DNA with enough code to make one protein.
Each protein contributes to a trait that is inherited.
5.
Gene pool = all the various alleles of all the genes in all the
members of a population
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6.
7.
B.
Gene flow = movement of alleles between populations
Mutation = Change in alleles
a.
Translocation
b.
Deletion
c.
Inversion
d.
Duplication
Population variations
members of population vary in function, physical appearance & behavior
C.
Reproductive potential vs reality
1.
Mathematical calc shows an animal population unchecked would
increase faster than food supply (Thomas Malthus, 1798)
2.
Available resources not sufficient to support all members of
population
3.
Only certain members of population survive & reproduce
D.
Survival of the Fittest
(Differential reproduction)
1.
Fitness = ability of individual to survive & reproduce in its local
environment
2.
Ex: Convergent evolution
a.
Dissimilar species living in similar environments have
similar physical appearances
b.
Ex.:
i. Sharks, seals, whales, penguins & sea turtles have
flippers
ii. Bats, birds & butterflies have wings
E.
Natural selection
1.
Stabilization selection - intermediate phenotype favored
2.
Disruptive selection – both extreme phenotypes favored
3.
Directional selection - one extreme phenotype favored
F.
Agents of evolutionary change
1.
Mutation = Raw material for evolutionary change
2.
Natural Selection
3.
Adaptive radiation = rapid development from 1 sp.  many
Occurs with lack of competition
a) Galapagos: tortoises; finches
b) Australia: marsupials
4.
Interruption of gene flow
(Gene flow keeps gene pools similar & large  Prevents
speciation)
a.
Reproductive isolation = increased chances of speciation
1) Allopatric speciation
Ex: geographic isolation
2
4.
5.
2) Sympatric speciation
a) Rare in animals
b) Polyploidy in some plants
Nonrandom mating = mating preference for particular phenotype
a.
Decreases # of heterozygotes
b.
Increases # of homozygotes
Genetic drift = changes in allelic frequencies due to chance
Most noticeable in small populations
a.
Founder Effect
When few individuals found new colony, bring only
fraction of original gene pool, which alleles are carried
determined by chance
Ex:
1) Smith Is.: blonde hair & blue eyes
2) Amish of Lancaster, PA
i. 1 in 14 carries recessive allele that causes
unusual form of dwarfism (affects lower arms/legs
only) and polydactylism (extra fingers)
ii. 1 in 1000 carries allele in pop. at large
b. Bottleneck effect = natural or manmade disaster drives
population to near extinction
1) Few individuals surviving = small gene pool
2) Surviving alleles selected by chance, not better
adapted (endangered species)
G.
VI.
Population NOT evolving
Frequency of alleles remains constant
Hardy - Weinberg rule
SUMMARY
Principle of Evolution - explanation of unity & diversity of life
MACROEVOLUTION
Reading fossils
Comparative embryology and early development
Comparative anatomy
MICROEVOLUTION
Comparative biochemistry
Proteins: yeasts & humans have 90% of the same proteins
DNA fingerprinting
3
1. 99% shared with chimpanzees (Jane Goodall)
2. 18 of 23 human chromosomes nearly identical to chimpanzees
& gorillas
Other 5 differ at inverted & translocated regions
VII.
HOMEWORK
DUE AT START OF NEXT LECTURE
Required: After reading these chapters, collect one living organism (See outline of
homework for details)
(Optional Extra Credit):
INDEPENDENT STUDY FOR EXTRA CREDIT: KINGDOM PROTISTA (See outline
of homework for details)
INDEPENDENT STUDY FOR EXTRA CREDIT: THE FUNGI KINGDOM (See
outline of homework for details)
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