Transcript GEOGRAPHICAL ISOLATION

EVOLUTION &
SPECIATION
VOCABULARY REVIEW
• EVOLUTION – CHANGE OVER TIME
• NATURAL SELECTION - INDIVIDUALS
BETTER ADAPTED TO THE
ENVIRONMENT ARE ABLE TO
SURVIVE & REPRODUCE.
– A.K.A. “SURVIVAL OF THE FITTEST”
NEW VOCABULARY
• POPULATION – GROUP OF
INDIVIDUALS OF SAME SPECIES
THAT INTERBREED
• GENE POOL – COMMON GROUP OF
ALL GENES PRESENT IN A
POPULATION
Gene Pool
Combined genetic
info. of all
members
Allele frequency is
# of times
alleles occur
Evolution of Populations
Occurs when there
is a change in
relative
frequency of
alleles (gene
pairs)
How natural selection works
Resistance to antibacterial soap
Generation 1: 1.00 not resistant
0.00 resistant
How natural selection works
Resistance to antibacterial soap
Generation 1: 1.00 not resistant
0.00 resistant
How natural selection works
Resistance to antibacterial soap
Generation 1: 1.00 not resistant
0.00 resistant
Generation 2: 0.96 not resistant
0.04 resistant
mutation!
How natural selection works
Resistance to antibacterial soap
Generation 1: 1.00 not resistant
0.00 resistant
Generation 2: 0.96 not resistant
0.04 resistant
Generation 3: 0.76 not resistant
0.24 resistant
How natural selection works
Resistance to antibacterial soap
Generation 1: 1.00 not resistant
0.00 resistant
Generation 2: 0.96 not resistant
0.04 resistant
Generation 3: 0.76 not resistant
0.24 resistant
Generation 4: 0.12 not resistant
0.88 resistant
Conditions needed for Genetic
Equilibrium
SPECIATION
• THE FORMATION OF NEW SPECIES
• AS NEW SPECIES EVOVLVE,
POPULATIONS BECOME
REPRODUCTIVELY ISOLATED
• REPRODUCTIVE ISOLATION –
MEMEBERS OF 2 POPULATIONS
CANNOT INTERBREED & PRODUCE
FERTILE OFFSPRING.
3 ISOLATING MECHANISMS……..
• BEHAVIORAL ISOLATION- CAPABLE OF
BREEDING BUT HAVE DIFFERENCES IN
COURTSHIP RITUALS (EX.
MEADOWLARKS)
• GEOGRAPHICAL ISOLATION –
SEPARATED BY GEOGRAPHIC BARRIERS
LIKE RIVERS, MOUNTAINS, OR BODIES
OF WATER (EX. SQUIRREL)
• TEMPORAL ISOLATION – 2 OR MORE
SPECIES REPRODUCE AT DIFFERENT
TIMES.
Fig. 23.6
Four species of leopard frogs: differ in their mating
calls. Hybrids are inevitable
Behavioral Isolation
These squirrels live on opposite sides of the Grand Canyon.
This is an example of Geographic Isolation
These 2 species of cricket mate (reproduce) at
different times of the year. This is an example of
Temporal Isolation
SPECIATION IN DARWIN’S
FINCHES
• SPECIAITON IN THE GALAPAGOS
FINCHES OCCURRED BY:
- FOUNDING OF A NEW POPULATION,
- GEOGRAPHIC ISOLATION which led to - REPRODUCTIVE ISOLATION and
CHANGES IN THE NEW POPULATION’S
GENE POOL due to COMPETITION.
Evidence of Evolution
1. Fossil Record
2. Geographic Distribution of Living
Species
3. Homologous Body structures
4. Similarities in Embryology
Evidence of
Evolution
Fossil Record
provides
evidence that
living things have
evolved
Fossils show the
history of life on
earth and how
different groups
of organisms
have changed
over time
Relative Dating
versus
Absolute Dating
Relative Dating
• Can determine a
fossil’s relative
age
• Performed by
estimating fossil
age compared
with that of
other fossils
• Drawbacks –
provides no info
about age in
years
Absolute dating
• Can determine the
absolute age in
numbers
• Is performed by
radioactive dating –
based on the amount
of remaining
radioactive isotopes
remain
• Drawbacks - part of
the fossil is
destroyed during the
test