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Evolution
Sec. 16.1
Darwin and Natural Selection
• Evolution: Change in a population over
time
• Galapagos Islands:
-located off the west coast of South
America
-Darwin studied species of animals and
plants; and found that species varied
between islands
GALAPAGOS ISLANDS
SPECIES VARIATION BETWEEN
ISLANDS
Mathus
• Discovered that the human population
growth outpaces the food supply
Darwin discovered species
compete for survival
• Food
• Space
• Finding mates
• Escaping predators
• Shelter
SURVIVAL OF THE FITTEST
• ONLY THE BEST FIT FOR THE
ENVIRONMENT SURVIVE TO
REPRODUCE!
DARWINS DISCOVERIES
• EACH GENERATION OF NEW SPECIES
SHOWS VARIATION IN TRAITS
THROUGH:
1. ARTIFICIAL SELECTION
2. NATURAL SELECTION
ARTIFICIAL SELECTION
• BREEDING ORGANISMS WITH SPECIFIC
TRAITS TO PRODUCE OFFSPRING WITH
IDENTICAL TRAITS
DOG BREEDING: EX. OF
ARTIFICAIL SELECTION
NATURAL SELECTION
• PROCESS OF SELECTION WHICH OCCURS
IN NATURE
• ORGANISMS WITH CERTAIN VARIATIONS
SURVIVE, REPRODUCE AND PASS
VARIATIONS TO NEXT GENERATION
• ORGANISMS WITHOUT THESE
VARIATIONS ARE LESS LIEKLY TO
SURVIVE AND REPRODUCE.
NATURAL SELECTION
Natural Selection:
ADAPTATIONS
• VARIATIONS THAT AID ORGANISMS IN
SURVIVAL IN THEIR ENVIRONMENT
• Ex: thorns on plants, distinct coloration of
animals
• Darwin believed adaptations occurred over
many generations.
Structural Adaptations
• Changes in an
organisms
appearance or
physical traits
MIMICRY
• Structural adaptation
•
that allows one
species to resemble
another
Harmless species
often adapt to look
like harmful to protect
themselves from
predators
CAMOUFLAGE
• STRUCTURAL
•
ADAPTATION THAT
ENABLES SPECIES TO
BLEND WITH THEIR
SURROUNDINGS
Prevents species from
being seem by
predators.
PHYSIOLOGICAL ADAPTATIONS
• Changes in an organisms metabolic
processes
• Ex: penicillin-resistant bacteria; pesticide
resistant insects and weeds
INDIRECT EVIDENCE OF
EVOLUTION
• Fossils
• Anatomy
• Embryology
• Biochemistry
1. Fossils
• Provide record of early life
• Ex: Camels
2. Anatomy
• Homologous structures: structures with
common evolutionary origin
- can be similar in structure, function,
or both
- believed structures are evidence of
evolution from an common ancestor
Homologous Structures
Ex: Forelimbs
2. Anatomy
• Analogous Structures: features that do
not have a common evolutionary origin
but are similar in function.
• Ex: Butterfly wing and Bird wing
Analogous Structures
2. Anatomy
• Vestigial Structures: structures that have
no function now but did in an ancestor
• A structure becomes vestigial when it is no
longer needed.
Vestigial Structure
Appendix is no longer used
in humans so it is
considered
a vestigial structure.
(need when we ate
more of
a plant based diet)
3. Embryology
• Easy to distinguish adult bird and mammal
but difficult to distinguish embryos.
• Embryo: earliest stage of growth and
development of an organism
• Suggest evolution of common ancestors
Embryology
4. Biochemistry
• Compares DNA and RNA of different
species to determine evolutionary
relationships
MECHANISMS OF EVOLUTION
SEC. 15.2
POPULATION GENETICS
• GENE POOL: ALL THE ALLELES OF A
POPULAITONS GENES
• ALLELE FREQUENCY: PERCENTAGE OF
A SPECIFIC ALLELE IN A POPULATION
• GENETIC EQUILIBRIUM: WHEN THE
ALLELE FREQUENCY REMAINS THE SAME
OVER GENERATIONS
CHANGES IN GENETIC
EQUILIBRUIUM
• GENETIC DRIFT
• NATURAL SELECTION:
– STABILIZING SELECTION
– DIRECTIONAL SELECTION
– DISRUTIVE SELECTION
GENETIC DRIFT
• ALTERATION OF ALLELIC FEQUENCIES BY
CHANCE EVENTS; COMMONLY OCCURS IN
SMALL POPULATIONS
• Ex: Amish Settlement in PA
– 1 in 14 (short arms, legs, extra fingers and
toes)
– 1 in 1000 in US population in general
STABILIZING SELECTION
• Favors average sized individuals
Small
cannot
compete
for food;
large are
seen by
predators.
SEE #1
DIRECTIONAL SELECTION
• Favors extreme variation
See #3
Elephants with
longer trunks are
able to reach
food/water more
easily.
DISRUPTIVE SELECTION
• Favors either extreme
See #2
Marine Limpets
with white, tan
and dark brown
shells. The
white and
brown are
camouflaged as
rocks while tan
are easily seen.
EVOLUTION OF SPECIES
(SPECIATION)
• SPECIES: Groups of organisms that look
alike and can interbreed to produce fertile
offspring
• SPECIATION: The evolution of a new
species
– Occurs when members of a population can no
longer interbreed and produce fertile
offspring.
Geographic Isolation
• Physical barrier divides population
REPRODUCTIVE ISOLAION
• GENETIC MATERIAL BECOMES TO
DIFFERENT TO MATE.
• BEHAVIOR: MAY MATE AT DIFFERENT
TIMES OF YEAR
• POLYPLOIDY: INDIVIDUALS WITH AN
EXTRA SET OF CHROMOSOMES CANNOT
MATE SUCCESSFULLY
REPRODUCTIVE ISOLATION
GRADUALISM VS. PUNCTUATED
EQQUILBRIUM
Gradualism
• Believes change will
happen slowly over
many generations
Punctuated
• Change is rapid and
then long periods of
equilibrium occur
between
PATTERNS OF EVOLUTION
• Adaptive radiation
– Ancestors evolve into an array of species to fit the
environment
• Divergent evolution
– Species becomes increasingly distinct from original
ancestor
• Convergent evolution
– Unrelated species that occupy similar environments in
different parts of the world undergo similar natural
selection
ADAPTAVIE RADIATION
DIVERGENT EVOLUTION
CONVERGENT EVOLUTION