UNIT ONE
1
EVOLUTION AND
SPECIATION
INTRODUCTION TO
EVOLUTION
2
MICROEVOLUTION
MICROEVOLUTION
3
 Individuals of all natural populations share a
common gene pool but differ in the alleles they each
inherit
 As a result of the variations in genotype, they show
variations in the phenotype
 Individuals do not evolve; populations do
MICROEVOLUTION
4
 This evolution occurs as a result of a change in the
alleles of that population’s gene pool
 Over the generations, any allele may increase in
frequency OR it may become rare or even lost
 Microevolution refers to changes in allele
frequencies as an out come of:
a) Mutation
b) Natural selection
c) Genetic drift
d) Gene flow
INTRODUCTION TO
EVOLUTION
5
GENETIC STRUCTURE OF
POPULATIONS
GENETIC STRUCTURE OF POPULATIONS
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 Population geneticists study heredity in groups of
individuals called a population
 Populations of the same species (ex: pigeons) share
morphological (morpho – form) traits:
a. 2 feathered wings
b. 3 toes forward, 1 toe back
 Populations also share physiological traits like
homeostatic mechanisms that help the body function
in it’s environment
 They also respond the same way to basic stimuli –
behavioral traits
GENETIC STRUCTURE OF POPULATIONS
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 The individuals of each population show variations
in the details of the traits they share with the other
members (i.e.: color/patterning of feathers on pigeon
wings)
 Almost every trait of any species may vary, but the
variety is far more pronounced in sexually
reproducing species
 Looking at our definition of a population, this variety
is the result of the combining and recombining of the
genes of two parents to create offspring
GENETIC STRUCTURE OF POPULATIONS
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Qualitative Differences
Quantitative Differences
 2 or more distinct
 Range of incrementally
forms (morphs)
 Dimorphism –
persistence of 2 forms
of a trait in a
population
 Polymorphism – 3 or
more forms of the trait
small variations in each
morph
 Typically unique to
specific populations
EVIDENCES OF EVOLUTION
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FOSSILS
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1. Mold fossils
2. Cast fossils
3. Permineralization (petrification)
4. Replacement fossils
5. Organic matter (teeth, bones)
6. Preservation
COMPARATIVE ANATOMY
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 Comparative Morphology – study of body forms and
structures of major groups of organisms
 Homologous structures – body parts that are
structurally similar but different in function; genes
for constructing these parts indicates shared
ancestry
 Analogous structures – structures that serve
similar functions but have different origins on
embryonic forms
 Vestigial structures – have no apparent function
in specific organism
12
COMPARATIVE EMBRYOLOGY
13
BIOGEOGRAPHY
14
COMPARATIVE BIOCHEMISTRY
15
FOSSIL DATING
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 Relative Dating – dating fossils relative to their
location in rock layers and to each other (estimate
only)
 Absolute Dating - determination of actual age of
fossil
1. Radioactive dating: use of specific radioactive
isotopes
2. Amino acid racemization: ratio of left-handed
amino acids (living) to right-handed (dead)