Transcript evolution and speciation ppt

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
Variation in Populations
2 processes can
lead to this:
Mutations change in DNA
sequence
Gene Shuffling –
from sexual
reproduction
Genetic Drift changes populations…….
• Random change in allele
frequency causes an allele to
become common
• Founder Effect:
a cause of genetic
drift attributable to
colonization by a
limited number of
individuals from a
parent population
• Gene Flow:
genetic exchange
due to the
migration of fertile
individuals or
gametes between
populations
(reduces
differences
between
populations)
• Nonrandom mating: inbreeding and
assortive mating (both shift
frequencies of different genotypes)
• Natural Selection:
differential
success in
reproduction;
only form of
microevolution
that adapts a
population to its
environment
Sexual selection
• Sexual
dimorphism:
secondary sex
characteristic
distinction
• Sexual selection:
selection towards
secondary sex
characteristics
that leads to
sexual
dimorphism
Evolution of Populations
Occurs when there
is a change in
relative
frequency of
alleles
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
Phenotype Expression
• Depends on
how many
genes control
that trait
Single-Gene vs. Polygenic Traits
Single-Gene:
2 Distinct Phenotypes (EG: tongue rolling)
Polygenic:
Many Phenotypes
Allele Frequencies
Natural Selection
Single Gene
Traits
Genetic Drift
Polygenic
Traits
Directional
Selection
Stabilizing Selection
Disruptive Selection
Natural Selection on Polygenic Traits
• Shifts to
middle range
• Shifts to
2 extremes
• Shifts to
1 extreme
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.
Table 23.1a
Tigon
Result of male tiger
and female lion
mating incaptivity.
Offspring are infertile.
Separated both
geographically and
ecologically.
Liger
Result of male lion and female
tiger mating in captivity.
Offspring are infertile.
Table 23.1b
Fig. 23.6
Four species of leopard frogs: differ in their
mating calls. Hybrids are inviable.
These squirrels live on opposite sides of the Grand
Canyon. This is an example of allopatric speciation.
Hawaiian Honeycreepers
An example of adaptive radiation –
these species all diverged from a
common ancestor (founder species)
FOUNDER SPECIES
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
Flying
Squirrel
Sugar
Glider
Marsupial Mammals
Convergent
Evolution
and
Analogous
Structures
Placental mammals
Mammalia
Rat like
common
ancestor
Big Question!!!
How did life arise on the big blue planet??
 Scientists attempt to answer this
question scientifically.
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
Carbon-14 Dating
Fossil Formation
Big Bang Theory
 A cosmic explosion that hurled matter and in all
directions created the universe 10-20 billion years
ago
 Evidence
 it explains why distant galaxies are traveling
away from us at great speeds
 Cosmic radiation from the explosion can be
observed
 The Big Bang theory probably will never be
proven; consequentially, leaving a number of tough,
unanswered questions.
What was early earth like?
Earth was Hot!!
Little or no oxygen
Gasses in atmosphere:
Hydrogen cyanide (poison to you!)
Hydrogen sulfide
Carbon dioxide
Carbon monoxide
Nitrogen
So how did the earth
get oxygen?
 Some of that oxygen was generated by
photosynthetic cyanobacteria
 Some came from the chemical
separation of water molecules into
oxygen and hydrogen.
 Oxygen drove some life
forms to extinction
 Others evolved ways of
using oxygen for respiration
How did life begin?
Miller and Urey’s
Experiment
 Passed sparks
through a mixture of
hydrogen methane
ammonia and water
 This produced
amino acids – the
building blocks of life
Miller’s
experiment
suggests that
lightning could
have produced
amino acids
How can simple amino
acids result in life?
There are 3 theories
1. Formation of microspheres
 Large organic molecules can
sometimes form tiny proteinoid
microspheres
 Store and release energy, selectively
permeable membranes, may have
acquired more characteristics of living
cells
nd
2
Hypothesis for Life
Evolution of RNA to DNA
• RNA was assembled
from simple organic
molecules in a
primordial soup
• RNA was able to
replicate itself and
eventually form DNA
• Not scientifically
proven to be possible
rd
3
Theory of Life
Endosymbiotic theory
eukaryotic cells
arose from living
communities formed
by prokaryotic
organisms
Ancient prokaryotes
entered primitive
eukaryotic cells and
remained there as
organelles