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Evolution
Chapters 13 and 14
What is evolution???
Youtube video
Evolution of Dance
Glossary of terms
Evolution
Fitness
Common descent
Adaptation
Fossil
Geological time scale
Relative dating
Radioactive element
Half life
Absolute dating
Sedimentary rock
paleontologist
fossil record
embryo
homologous structure
vestigial structure
CHARLES DARWIN
1809-1882
TRIP ON THE BEAGLE
• 1830’S BEAGLE
• TOURED AROUND THE WORLD
• SPENT TIME ON THE GALAPAGOS ISLANDS-OFF
THE COAST OF ECUADOR
• TRIP LASTED 5 YEARS
• COLLECTED MANY SAMPLES, SPECIMENS AND
SENT THEM HOME
• KEPT A JOURNAL OF HIS OBSERVATIONS FOR
THE ENTIRE TRIP
He saw that there were similar distinctions between
species that inhabited the various Galapagos
islands’
Organisms that were different than their ancestors
through adaptation
DARWIN’S OBSERVATIONS ON HIS TRIP
• HE SAW MUCH DIVERISTY IN ANIMALS AND
PLANTS AND FOUND FOSSILS OF THINGS NO
LONGER LIVING
• HE REALIZED THERE ARE AN ENORMOUS AMOUNT
OF SPECIES ON EARTH
• TODAY’S ESTIMATE-3-20 MILLION
• BUT MORE THEN 99.9% OF ALL SPECIES THAT
EVER LIVED ARE NOW EXTINCT
DARWIN WONDERED:
WHERE DID ALL THESE SPECIES COME
FROM AND WHY DID SOME DISAPPEAR?
MORE OBSERVATIONS OF DARWIN
HE SAW MANY WAYS THAT ORGANISMS SURVIVED
AND REPRODUCED
HE CALLED THIS FITNESS - PHYSICAL TRAITS &
BEHAVIORS WHICH ENABLE ORGANISMS TO
SURVIVE/REPRODUCE IN THEIR
ENVIRONMENT
DARWIN WONDERED:
HOW DID THESE ORGANISMS DEVELOP
STRUCTURES THAT GAVE THEM THIS FITNESS?
WHY WERE THERE SO MANY TECHNIQUES TO
SURVIVAL?
DARWIN RETURNS HOME
• HE BECAME VERY POPULAR DUE TO ALL THE
SPECIMENS, SAMPLES HE SENT BACK
• HE BECAME FRIENDS WITH CHARLES LYELL, A
GEOLOGIST
THE AGE OF THE EARTH
IN THE 18TH AND 19TH CENTURY SCIENTISTS
HYPOTHESISED THAT THE EARTH IS VERY
OLD, & CHANGED VERY SLOWLY DUE TO
NATURAL FORCES-WIND, RAIN, ETC.
• SCIENTISTS SAW THAT THE EARTH MOVED &
SHIFTED
• SOME ROCK LAYERS BURY OTHERS & PUSH
APART THE SEA FLOOR
• THEY FOUND FOSSILS THAT RESEMBLED
ORGANISMS STILL ALIVE, BUT OTHERS DID NOT
• THIS INFLUENCED DARWIN’S THINKING ABOUT
EVOLUTION
CHARLES LYELL
STATED, “THE EARTH MUST BE VERY OLD
SINCE GEOLOGICAL FORMATIONS ARE
SLOW & GRADUAL”
“SCIENTISTS MUST EXPLAIN PAST EVENTS
AS PROCESSES THEY CAN OBSERVE. THIS
IS HOW THE SCIENTIFIC METHOD
WORKS.”
Charles Lyell – Principles of Geology
A book that emphasized the great age
of earth and the principles of
uniformitarianism
Uniformitarianism – the geological structure
of the earth resulted from cycles of
observable processes and that these same
processes operate continuously through
time
Ex. Sediment deposition in rivers
These ideas influenced Darwin and he saw
how the same principles could apply to
organisms
•IN 1859, DARWIN’S “THE ORIGIN OF
SPECIES” IS PUBLISHED
•THIS IS 30 YRS. AFTER HIS TRIP ON THE
BEAGLE – IT WAS A RADICAL IDEA FOR
THE TIME
http://www.pbs.org/wgbh/evolution/darwin/index.html
•DARWIN’S BOOK CONTAINED 5 KEY
CONCEPTS
5Key concepts
Contained in the book
1.MODERN ORGANISMS ARISE
THROUGH EVOLUTION
2. EACH SPECIES COMES FROM A
PRECEDING ONE, THEY HAVE A
COMMON ANCESTOR. COMMON
DESCENT
3. FITNESS COMES FROM
ADAPTATION
4. SUCCESSFUL ADAPTATION
ALLOWS ORGANISMS TO
SURVIVE & REPRODUCE
5. ADAPTATION IS ANY
CHARACTERISTIC THAT
INCREASES AN ORGANISM’S
FITNESS
DO NOW
1. HOW LONG WAS DARWIN GONE ON HIS TRIP?
2. WHAT WAS THE NAME OF HIS BOOK?
3. DARWIN SAID, EACH SPECIES COMES FROM A
COMMON ANCESTOR. WHAT IS THIS CALLED AS
PART OF HIS THEORY OF EVOLUTION?
GEOLOGICAL TIME SCALE
GEOLOGICAL TIME-KEY EVENTS
• 3.6 B.Y.A.-1 CELLS
• 580 M.Y.A.-AQUATIC PLANTS-ALGAE
• 360 M.Y.A.-BONY FISH, AMPHIBIANS, INSECTS
ST
GEOLOGICAL TIME-KEY EVENTS
• 245 M.Y.A.-PERMIAN EXTINCTION-MARINE
ANIMALS
• 144 M.Y.A. JURASSIC-AGE OF THE DINOSAURS
• 65 M.Y.A.-CRETACEOUS-EXTINCTION OF
DINOSOURS
GEOLOGICAL TIME-KEY EVENTS
•65 M.Y.A –RADIATION (SPREADING) OF
MAMMALS
•39 M.Y.A. –PRIMATES EMERGE
•7 M.Y.A.-APELIKE ANCESTORS APPEAR
•2.5 M.Y.A.-HUMANS APPEAR
But how do scientists know when
certain things happened or when
certain organisms lived???
RELATIVE DATING-NOT DATING YOUR COUSIN!
• GEOLOGIST IN THE PAST NOTICED THAT
CERTAIN TYPES OF ROCK COULD ALWAYS BE
FOUND IN THE SAME VERTICAL ORDER
• AGE OF ROCK CAN BE ESTIMATED BY THE
POSITION IN THE ROCK LAYERS
• OLDER LAYERS AT THE BOTTOM, NEWER ON
TOP
RELATIVE DATING
• Relative Dating – technique to date fossils
relative to other fossils in the rocks
• Law of Superposition – successive layers of rock
or soil were deposited on top of one another by
wind or water
lowest layers are the oldest
top layers are the youngest
–
–
RELATIVE DATING OF FOSSILS
IF A FOSSIL IS IN A TOP LAYER-IT MUST
BE?
IF A FOSSIL IS IN A BOTTOM LAYER IT
MUST BE?
CAN EXACT AGE BE DETERMINED WITH
THIS METHOD?
RADIOACTIVE DATING-YOU HAVE A GLOW ABOUT
YOU!
http://www.pbs.org/wgbh/evolution/library/03/3/l_033_01.html
• THE AGE OF ROCK CAN BE DETERMINED BY
THE ELEMENTS IT IS COMPOSED OF
• MANY ELEMENTS ARE ISOTOPESRADIOACTIVE
• THE ATOMS DECAY OVER TIME-SO…
RADIOACTIVE DATING CONT.
• WHEN THE ATOMS DECAY THIS CHANGES
THEIR CHEMICAL IDENTITY
• RADIOACTIVE DECAY CAN BE MEASURED AS
HALF LIFE
• HALF LIFE IS THE TIME IT TAKES FOR HALF
THE ATOMS TO DECAY
URANIUM 238/POTASSIUM 40
URANIUM TURNS INTO LEAD AS IT DECAYS - HALF LIFE OF 4.5 BILLION YEARS
POTASSIUM TURNS INTO ARGON AS IT
DECAYS – HALF LIFE OF 1.3 BILLION
YEARS.
SCIENTISTS CAN DETERMINE ROCK AGES
USING RATIOS
FOSSILS FOUND IN THE ROCK THAT ARE
DATED ARE ASSUMED TO BE THE SAME AGE
AS THE ROCKS
C14, CARBON DATING FOR ONCE LIVING
ORGANISMS
• C14 CARBON – HALF LIFE OF 5770 YEARS
• CARBON CAN EXIST AS RADIOACTIVE C14
OR NON RADIOACTIVE C12
• IN 5770 YEARS ½ THE C-14 TURNS INTO
N-14
C14, CARBON DATING
• THEY CAN THEN DETERMINE THE AGE OF
THESE CELLS
• THIS METHOD IS ONLY GOOD FOR ITEMS <
60,000 Y.O.
• OFTEN DATE PRE-HISTORIC HUMANS
USING THIS METHOD
DO NOW
1. C14 DATING IS GOOD FOR ITEMS THAT
ARE > 1MILLION YEARS OLD, True OR
False?
2. WHEN URANIUM DECAYS IT
BECOMES_______?
3. WHAT IS THE DEFINITION OF HALF LIFE?
4. MOST FOSSILS ARE MADE FROM WHAT
TYPE OF ROCK?
Fossils
•Found in the rocks
•Preserved ancient remains of organisms
•Some fossils looked like organisms that
were alive – others did not
•The fossil record shows animals that were
•
preserved by being buried in the rocks, tar
pits or tree sap
Sedimentary rock-layers of sediment cover
up the animals and preserve the remains
The fossil record shows that change
followed change on earth.
FOSSIL RECORD-INFORMATION OF PAST FORMS OF LIFE
• TELLS OF MAJOR CHANGES IN THE
GEOLOGICAL RECORD OF EARTH
• SEA CREATURES IN ARIZONA,-COASTLINE
CHANGES
• GIANT FERNS IN N. AMERICA-WARMER
CLIMATE
• WHAT DOES A PALEONTOLOGIST STUDY?
FORMATION OF FOSSILS
http://www.pbs.org/wgbh/evolution/library/04/3/l_043_01.html
• MOST ARE FOUND IN SEDIMENTARY ROCK-
SEDIMENT FORMS WHEN SAND & SILT
FROM WATER SETTLE TO THE BOTTOM OF A
BODY OF WATER
• ANIMALS & PLANTS THAT DIE IN THE
WATER ARE COMPRESSED INTO ROCK BY
PRESSURE FROM THE WATER.
FOSSIL FORMATION
http://www.classzone.com/books/earth_science/ter
c/content/visualizations/es2901/es2901page01.cf
m?chapter_no=visualization
FORMATION OF FOSSILS
• BONES & TEETH MAY BE PRESERVED ON
LAND BY SHIFTING SAND, MUD OR
VOLCANIC ASH.
• FOOTPRINTS OR SOFT TISSUE CAN BE
PRESERVED IF THEY FILL WITH DUST OR
ASH. THEY ARE THEN COVERED BY OTHER
MATERIALS & HARDEN
FORMATION OF FOSSILS
•PETRIFICATION CAN OCCUR WHEN
REMAINS ARE COVERED WITH WATER
•DISSOLVED MINERALS FROM THE WATER
REPLACE THE DECAYING TISSUES &
HARDEN
Petrified wood
GAPS IN THE FOSSIL RECORD
•WHY ARE THERE GAPS?
•CONDITIONS TO FORM FOSSILS NOT
PRESENT
•SOME TISSUES ARE TOO SOFT TO FORM
FOSSILS-JELLY FISH, WORMS
•EROSION DESTROYS FOSSILS
•FOSSILS CAN BE BURIED AND NOT
FOUND
DO NOW
1. Which make better fossils, bone or
footprints?
2. Why are there gaps in the fossil
record?
3. Which is the cast & which one is the
mold of a fossil below?
COMPARISON OF LIVING ORGANISMS
http://www.pbs.org/wgbh/evolution/library/04/2/l_042_02.html
EMBRYOLOGY
• CHARACTERISICS LOST IN ADULTHOOD ARE
SEEN IN EMBRYOS
• ALL VERTEBRATE EMBRYOS HAVE GILL
POUCHES-NECK FOLDS
• IN FISH DEVELOP INTO GILLS
• IN HUMANS-TRACHEA
• INHERITANCE FROM A FISH-LIKE ANCESTOR
Evidence of evolution
Embryo evidence: embryos of different species look
identical early in development, and change as they
grow
EMBRYOLOGY
•THE COMMON ANCESTOR OF THESE
•
•
ORGANISMS PASSED ON A SINGLE
GENETIC PATTERN OF DEVELOPMENT
MUTATIONS PASSED ON CHANGES TO
THE ADULT ANIMAL TO CREATE THE
DIFFERENCES IN ADULTHOOD
TODAYS GENES FOR EMBRYO
DEVELOPMENT HAVE CHANGED LITTLE
FROM THE PAST. CONSERVED GENES
Similarities in body structure
Homologous structures:
the limbs of different organisms are based on the
same pattern of bones
Each type of limb is adapted in a different way to
help the organisms survive in its environment
Vestigial structures:
An organ that is so reduced in size or function that it
becomes a trace of what it used to be
COMPARATIVE ANATOMY
• HOMOLOGOUS STRUCTURES -SIMILAR
•
STRUCTURES DUE TO A COMMON
ANCESTOR
FORELIMBS
COMPARATIVE ANATOMY
• ANALOGOUS STRUCTURES -LOOK SIMILAR
BUT ARE USED FOR DIFFERENT PURPOSES.
• NOT FROM A COMMON ANCESTOR
COMPARATIVE ANATOMY
VESTIGIAL STRUCTURES -INHERITED FROM
AN ANCESTOR BUT no longer used by
modern organism
 An organism with a vestigial feature
probably shares common ancestor with an
organism that has a functional version of
the same feature
COMPARATIVE BIOCHEMISTRY
• GENETIC MATERIAL EXISTS IN EVERY LIFE FORM
• ORGANISMS W/A RECENT COMMON ANCESTOR
HAVE SIMILAR GENETIC MAKEUP.
• COMPARISON OF THE GENETIC SEQUENCES CAN
SHOW HOW CLOSELY RELATED ORGANISMS ARE
TO EACH OTHER
• HAS CREATED RETHINKING OF SOME ANCESTRY
OF ORGANISMS
CLADOGRAM-shows ancestral relationships, timeline
http://www.pbs.org/wgbh/evolution/change/family/
OLD SCHOOL THINKING
NEW SCHOOL
OLD SCHOOL
NEW SCHOOL
Evolution
The process by which modern organisms
have descended from ancient organisms
Chapter 14
A CHANGE IN A POPULATION OVER TIME
EARLY EXPLANATION FOR EVOLUTIONARY
CHANGE
•TO EXPLAIN FOSSILS, EARLY
•
SCIENTISTS HYPOTHESIZED THAT
CATASTROPHES OCCURRED
Punctuated equalibrium versus
gradualism
•AFTER EACH CATASTROPHE NEW
LIFE WOULD DEVELOP
•WERE THEY INCORRECT IN THIS
LOGIC?
I. JEAN BAPTIST LAMARCK
1744-1829
Jean Baptiste Lamarck
A FRENCH NATURALIST, IN CHARGE OF
THE INVERTEBRATES AT THE HISTORY
MUSEUM IN PARIS IN THE EARLY 1800’S
One of the first scientists to notice that:
1. living things change over time
2. organisms are adapted to their
environment
THREE ASSUMPTIONS (INCORRECT) OF
LAMARCK’S THEORY
1. ORGANISMS WILL ALWAYS TRY TO
IMPROVE & BECOME ADVANCED
2. THE EFFORT TO IMPROVE CAUSES THE
MOST USED STRUCTURES TO EVOLVE
WHILE OTHER PARTS ARE WASTED AKAPRINCIPLE OF USE AND DISUSE
3. ONCE A BODY STRUCTURE IS MODIFIED BY
USE OR DISUSE THE MODIFICATION IS
INHERITED AKA INHERITANCE OF
AQUIRED CHARACTERISITICS
BUT……
 Lamarck paved the way for Darwin
 First to come up with a theory
 Brought attention to how organisms
change
II. AUGUST WEISMANN 1834-1914
AUGUST WEISMANN
• DISPROVED LAMARCK THEORY ON INHERITED
CHARACTERISTICS DUE TO USE/DISUSE
• CUT OFF THE TAILS OF 22 GENERATIONS OF
MICE
• WHAT WOULD LAMARCK PREDICT?
• ALL MICE WERE BORN WITH TAILS
• AQUIRED CHARACTERISTICS ARE NOT
INHERITABLE
• CHANGES IN INDIVIDUALS DO NOT AFFECT
REPROD. CELLS OR OFFSPRING
Ideas that helped shape Darwin’s
theory of Evolution
1. Principles Of Geology by Lyell
 Earth is old
 Lots of time is needed for evolution
 Geological phenomena could transform the
face of earth over time
 If earth could change then life could
change
2. Farmers – Artificial Selection
 Domesticated organisms vary a
great deal
 Inheritable variations
 Variation happened or not
 Selectively bred for traits
Artificial Selection
 Intervention of humans ensures that only
individuals with the more desirable traits
reproduce
B. THOMAS MALTHUS 1766-1834
• CLERGYMAN WHO WROTE ABOUT ECONOMICS
•
WHO WROTE ESSAY “PRINCIPLE OF
POPULATION”
HE SAID “THE HUMAN POPULATION WAS
GROWING SO FAST THAT RESOURCES WOULD
SOON RUN OUT, PEOPLE WOULD DIE DUE TO
DISEASE, WAR & OTHER DISASTERS”
THOMAS MALTHUS CONT.
http://www.pbs.org/wgbh/evolution/library/02/5/l_025_01.html
•PLANTS & ANIMALS PRODUCE FAR MORE
OFFSPRING THEN CAN SURVIVE
•HE SUGGESTED THAT LOWER CLASS
FAMILY SIZE BE REGULATED SO THEY
CAN NOT PRODUCE MORE THEN THEY
CAN SUPPORT
IV. MAJOR COMPONENTS OF DARWIN’S NATURAL
SELECTION THEORY
1844 DARWIN WROTE HIS THEORY ON
EVOLUTION-CALLED IT NATURAL
SELECTION
THERE ARE 5 POINTS TO HIS THEORY
1. VARIATION IN POPULATION-VARIATIONS
ARE PASSED ON FROM PARENT TO
OFFSPRING
IV. MAJOR COMPONENTS OF DARWIN’S NATURAL
SELECTION THEORY
2. SOME VARIATIONS ARE FAVORABLE-IF
FAVORABLE , IT IMPROVES THE
ORGANISMS ABILITY TO LIVE &
REPRODUCE
DARWIN’S INFLUENCE FROM MALTHUS & LYELL
3. MORE YOUNG ARE PRODUCED THAN CAN
SURVIVE-ONLY A FEW LIVE LONG ENOUGH
TO REPRODUCE
4. Better adapted organisms are likely to live
longer and produce more offspring-A
LARGER & LARGER PORTION OF THE NEXT
GENERATIONS WILL INHERIT THESE
FAVORABLE VARIATIONS
5. GRADUALISM-OVER A LARGE AMOUNT OF
TIME, SMALL CHANGES ACCUMULATE &
POPULATIONS CHANGE
Evolution happens by Natural Selection
How it works:
 Variation in a population
 More organisms are produced than can fit in
the environment
 Struggle to survive – against environment
and each other
 Organisms that are well suited to their
environment survive (survival of the
fittest)
 Organisms not well suited die
 Well suited organisms go on to reproduce and
pass on their well suited traits (Adaptations)
 Overtime this will slowly change a species
V. NATURAL SELECTION IN PEPPERED MOTHS
KETTLEWELL’S OBSERVATION
• BEFORE THE INDUSTRIAL REVOLUTION IN
•
ENGLAND IN THE LATE 1700’S, THE FOREST
WERE COVERED IN SPOTTED LICHEN
SPOTTED MOTHS COULD BLEND INTO THE BARK
COVERED WITH LICHEN
PEPPERED MOTHS
http://bcs.whfreeman.com/thelifewire/content/chp23/2302001.html
• BLACK MOTHS WERE EASY TO SEE AND WERE
EATEN BY PREDATORS
• AFTER THE INDUSTRIAL REVOLUTION-LICHEN
STARTED TO TURN BLACK FROM THE SOOT
• BLACK MOTHS WERE NOW HARDER TO SEE SO…
• SOON THE SPOTTED MOTH POPULATION
•
STARTED TO DECLINE & BLACK MOTHS
INCREASED
THE BLACK MOTHS HAD ADAPTED TO THE
ENVIRONMENT
PEPPERED MOTHS CONTINUED
• 1950’S H.B.D KETTELWELL HYPOTHESIZED
•
•
•
•
THAT SOMETHING IN INDUSTRIAL REGIONS
CAUSED THE DARK GRAY MOTH TO BE MORE
SUCCESSFUL THAN LIGHT GRAY MOTHS.
WHAT WAS IT?
THE DARK GRAY MOTHS’ ABILITY TO BLEND
INTO THEIR HABITAT AND AVOID PREDATION.
DARWIN WOULD CALL THIS?
FITNESS!
DO NOW
1. Who worked in the invertebrate
collection at a museum in Paris?
2. List one of his principles of evolution
3. Who wrote a book on economics that
influenced Darwin?
4. What did August Weisman do as an
experiment?
5. What caused the Peppered Moth’s
population to change?
Species
 A group of similar looking organisms
that breed with one another and
produce fertile offspring in their
natural environment
VI. POPULATION GENETICS
•SCIENTISTS STUDY GENETIC TRAITS IN A
POPULATION OVER TIME
•POPULATION OF THE SAME SPECIES CAN
•
BREED SO THEY SHARE A GENE POOLCOMBINED GENETIC MAKEUP OF ALL
MEMBERS IN A POPULATION
REMEMBER-GENES COME IN TWO
ALLELES, IN A GENE POOL EACH ALLELE
REPRESENTS A TRAIT
POPULATION GENETICS CONTINUED
THE NUMBER OF TIMES AN ALLELE
OCCURS IN A GENE POOL COMPARED
TO THE NUMBER OF TIMES OTHER
ALLELES OCCUR IS CALLED-THE
RELATIVE FREQUENCY OF THAT
ALLELE
RELATIVE FREQUENCY AN EXAMPLE
•SUPPOSE HALF A POPULATION
OF
PLANTS HAS AN ALLELE OF T FOR TALL
HEIGHT, THEN THE RELATIVE FREQUENCY
FOR THE TALL ALLELE IS 50%
•SCIENTISTS LOOK AT ALLELE FREQUENCY
CHANGES IN A POPULATION AS
BIOLOGICAL EVOLUTION
VII. DEVELOPMENT OF NEW SPECIES
•NICHE-ROLE AN ORGANISM PLAYS IN IT’S
•
•
ENVIRONMENT. NO TWO SPECIES CAN
OCCUPY THE SAME NICHE OVER A LONG
TIME PERIOD
COMPETITION CAUSES ONE TO ADAPT OR
LOOSE OUT
ONES WITH FAVORABLE TRAITS SURVIVE
& REPRODUCE PASSING ON THEIR TRAITS
THE PROCESS OF SPECIATION
REPRODUCTIVE ISOLATION-WHEN SPECIES
ARE SEPARATED NEW SPECIES CAN EVOLVE
HOW? geographic separation-rivers, mts.,
earthquakes
• CAN RESULT IN DIFFERENT BREEDING
TIMES, BEHAVIOR
• THE GENE POOL BECOMES CHANGED OVER
TIME DUE TO DIFFERENCES IN
ADAPTATION TO GEOGRAPHIC CHANGE
• OVER TIME THEY BECOME DIFFERENT
SPECIES
THE PROCESS OF SPECIATION
• ADAPTIVE RADIATION-ONE SPECIES GIVES RISE
TO NEW ONES
• WHEN ADAPTIVE RADATION OCCURS A NUMBER
OF SPECIES CAN MOVE AWAY FROM THE
ORIGINAL AREA-DIVERGENT EVOLUTION. EX.
LIMBS IN VERTEBRATES HAVE CHANGED INTO
DIFF. SHAPES
COVERGENT EVOLUTION. WINGS OF BATS & BIRDS
These have a different evolutionary origin, but
various species adopted similar strategies.
GENETIC DRIFT
http://www.wadsworthmedia.com/biology/0495119814_starr/big_picture/ch16_bp.swf
•AN ACCIDENTAL CHANGE IN GENE
FREQUENCY-CATASTROPHES
•FIRE DESTROYS WHITE FLOWERS AND
LEAVES MORE RED-CHANCE
•THE ALLELE FOR RED FLOWERS
INCREASES IN THE GENE POOL
14-3 Genetics and Evolutionary Theory
 Darwin did not know anything about
genetics
 Genes are the source of variation
 Mutations cause variations
 Meiosis causes variation as genes are
 given to gametes.
 Natural selection works on an organisms
phenotype
Example of Speciation
 Darwin’s finches
 13 species on Galapagos Islands
 Different beaks, different food, different
habitat
How the speciation of finches
occurred
 Founding male and female find their way
to – Island A
 Separation of populations – a couple of
birds get to – Island B
 Changes in the gene pool occur as the
birds adapt to their unique environments
 Reproductive isolation occurs
 Sharing the same island – coexistence,
evolution, extinction
http://www.britannica.com/EBchecked
/topicvideo/66391/16514/Galapagosfinches-have-evolved-manyadaptations-that-allow-them-to
http://www.youtube.com/watch?v=l
25MBq8T77w