UNIT ONE - Alvin ISD
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Transcript UNIT ONE - Alvin ISD
UNIT ONE
1
EVOLUTION AND
SPECIATION
INTRODUCTION TO
EVOLUTION
2
MICROEVOLUTION
MICROEVOLUTION
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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
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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
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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
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COMPARATIVE EMBRYOLOGY
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BIOGEOGRAPHY
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COMPARATIVE BIOCHEMISTRY
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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)