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Evolution
What is Evolution? How did this theory begin?
 EVOLUTION is the change in populations over time.
 Where did Darwin make observation to consider the
possibility that species change over time?
GALAPAGOS ISLAND
 Why was the HMS Beagle important to Darwin’s
studies? HE WAS THE SHIP’S NATURALISTS WHO
STUDIED AND COLLECTED BIOLOGICAL
SPECIMENS AT EVERY PORT
Types of Selection
 What is artificial selection? BREEDING
ORGANISMS WITH SPECIFIC TRAITS IN ORDER
TO PRODUCE OFFSPRING WITH IDENTICAL
TRAITS
 NATURAL SELECTION IS A MECHANISM FOR
CHANGE IN POPULATIONS. IT OCCURS WHEN
ORGANISMS WITH CERTAIN VARIATIONS
SURVIVE, REPRODUCE, AND PASS THEIR
VARIATIONS TO THE NEXT GENERATION.
4 Basic Principles of Natural Selection
 ORGANISMS PRODUCE MORE OFFSPRING THAN
CAN SURVIVE
 IN POPULATIONS, INDIVIDUALS HAVE
VARIATIONS.
 INDIVIDUALS WITH CERTAIN USEFUL VARIATIONS
SURVIVE IN THEIR ENVIRONMENT *Industrial
Melanism (peppered moth)
 OVER TIME, OFFSPRING WITH CERTAIN
VARIATIONS MAKE UP MOST OF THE POPULATION
AND MAY LOOK ENTIRELY DIFFERENT FROM
THEIR ANCESTORS.
Evidence of Evolution: FOSSILS
 FOSSILS shape the ideas of evolution
Evidence of Evolution:
STRUCTURAL ADAPTATIONS
 1. STRUCTURAL adaptations (morphological)
 A. Obvious examples- Mole-rats have large teeth and claws
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for digging better tunnels.
B. Subtle examples:
a. Mimicry – Viceroy and Monarch Butterflies; yellow
jacket wasp and syrphid fly
b. Camouflage
1. Cryptic Coloration- leaf frog, tree frog, chameleon
2. Counter Shading – bass
c. Warning Colors – skunk, coral snake
Coral snake – red on yellow will kill a fellow
King Snake – red on black is a friend of Jack.
Evidence of Evolution:
ADAPTATIONS PHYSIOLOGICAL
 2. PHYSIOLOGICAL adaptations – changes in an
organism’s metabolic processes.
Examples:
a. Bacteria have developed a resistance to the
medicine penicillin.
b. Insects and weeds have become resistant to the
chemicals in pesticides.
Evidence of Evolution:
BEHAVIORAL ADAPTATIONS
 BEHAVIORAL adaptations – action in a species for
survival.
Examples
a. Fish swim in schools for protections.
b. Male lions fight to maintain territory.
Evidence of Evolution: Anatomy of Organisms
 Anatomy of organisms:
1. Homologous structures-COMMON STRUCTURAL FEATURES
WITH A COMMON EVOLUTIONARY ORIGIN; SIMILAR IS
ARRANGEMENT, IN FUNCTION, OR IN BOTH
EXAMPLES: WHALE FORELIMB, CROCODILE FORELIMB,
BIRD WING
2. Analogous structures- DO NOT HAVE COMMON EVOLUTIONARY
ORIGIN, BUT ARE SIMILAR IN FUNCTION
EXAMPLES - BIRD WING AND BUTTERFLY WING
3. Vestigial structures-A STRUCTURE OR ORGAN THAT SUGGEST
EVOLUTIONARY RELATIONSHIP BUT HAVE NO KNOWN
FUNCTION IN A PRESENT DAY ORGANISM
EXAMPLES – HUMAN APPENDIX, REMAINS OF THE
NICTITATING MEMBRANE ON THE HUMAN EYE
Evidence of Evolution:
Embryology and Biochemistry
 Embryology –EMBRYOS OF FISH, REPITLE, BIRD
AND MAMMAL ARE MUCH THE SAME WITH
GILL SLITS AND A TAIL
 Biochemistry – DNA AND RNA COMPARISON –
USED AS THE BASIS FOR MODERN
CLASSIFICATION
What is meant by Population Genetics?
 EACH MEMBER OF THE POPULATION HAS THE
GENES THAT CHARACTERIZE THE TRAITS OF
THE SPECIES, AND THESE GENES EXIST AS
PAIRS OF ALLELES. JUST AS INDIVIDUALS
MAKE UP POPULATIONS, ALL OF THE GENES OF
THE INDIVIDUALS MAKE UP THE
POPULATION’S GENES.
What is a gene pool?
 ALL OF THE POPULATION’S GENES BROUGHT
TOGETHER
What is allelic frequency?
 THE PERCENTAGE OF ANY SPECIFIC ALLELE IN
THE GENE POOL – HOW OFTEN A TRAIT SHOWS
UP IN A POPULATION
 What is genetic equilibrium? THE FREQUENCY OF
ALLELES REMAIN THE SAME IN A POPULATION
FOR GENERATIONS
What causes changes in genetic equilibrium?
 ANY FACTOR THAT DISRUPTS THE ALLELIC FREQUENCY WILL
DISRUPT THE PHENOTYPE:
 EXAMPLES:
1. MUTATIONS – ENVIRONMENTAL FACTORS (chemicals or radiation)
OR GENETIC FACTORS BY NATURAL SELECTION
2. GENETIC DRIFT –
a. Small population that include the descendants of a small number of
organisms: example – The Amish of Lancaster County, Pennsylvania one
of the 30 settlers in this community carried the recessive genes that
resulted in short arms and legs and extra fingers and toes. Today 1 in 14
have these traits rather than the 1 in 1000 in the larger population of the
U.S.A.
b. movement of individuals in and out of a population –
Individuals leave a population, their genes are lost from the gene pool.
Individuals move into population, their genes are added to the gene pool.
3 types of Natural Selection that Act on Variation
 A. STABILIZING SELECTION FAVORS AVERAGE
INDIVIDUALS IN A POPULATION AND REDUCES
VARIATION IN A POPULATION.
 B. DIRECTIONAL SELECTION FAVORS ONE OF THE
EXTREME VARIATIONS OF A TRAIT AND CAN LEAD
TO THE RAPID EVOLUTION OF A POPULATION
 C. DISRUPTIVE SELECTION FAVORS BOTH
EXTREME VARIATIONS OF A TRAIT, RESULTING
EVENTUALLY IN NO INTERMEDIATE FORMS OF
THE TRAIT AND LEADING TO THE EVOLUTION OF
TWO NEW SPECIES.
Speciation
 What is speciation? OCCURS WHEN MEMBERS OF
THE SIMILAR POPULATIONS NO LONGER
 INTERBREED TO PRODUCE FERTILE
OFFSPRING WITHIN THEIR NATURAL
ENVIRONMENT.
 (the formation of a new species)
Causes of Speciation
 a. Geographic Isolation – members of a population
are separated by a structural object like a river,
ocean, mountain range, pond, lake
 b. Reproductive (Temporal) Isolation
1. mating seasons
2. mating habits
 c. Change in the number of chromosomes –
polyploidy – DNA is not compatible.
Occurrence of Speciation
 a. Gradualism – ORGANISMS SLOWLY CHANGE
OVER A LONG PERIOD OF TIME
 b. Punctuated Equilibrium-A MAJOR CASTROPHE
HAPPENS AND ORGANISMS CHANGE QUICKLY
Patterns of Evolution
 a. Adaptive Radiation- COMMON ANCESTOR EVOLVED INTO DIFFERENT
SPECIES
EXAMPLE –
ANCESTRAL LASAN FINCH
MAUI PARROT BILL CRESTED HONEY CREEPER
GROSBEAK FINCH
 b. Divergent evolution- IS ADAPTIVE RADIATION; ORGANISMS BECOME LESS
ALIKE
OVER TIME
 c. Convergent evolution- ORGANISM HAVE DIFFERENT ANCESTORS BUT
BECOME MORE
ALIKE IN TIME
EXAMPLE: WATER LIVING ANCESTOR
LAND LIVING ANCESTOR
(GILL SLITS) SHARK
DOLPHIN (LUNGS)
TORPEDO SHAPED BODY
LIVE IN WATER
Primates
 Primate – MAMMALS THAT INCLUDE LEMURS,
MONKEYS, APES, HUMAN
- Opposable thumb- GRASP- THUMB CAN CROSS
THE HAND
- Prehensile tail- GRASP – 5TH LIMB - MONKEYS
Types of Primates
 Hominids- WALK UP RIGHT
 TWO GROUPS: 1. GORILLAS AND CHIMPANZEES
HUMAN
 Bipedal- ABLE TO WALK ON TWO LEGS