• EVOLUTION – CHANGE OVER TIME
• NATURAL SELECTION - INDIVIDUALS
BETTER ADAPTED TO THE
ENVIRONMENT ARE ABLE TO
SURVIVE & REPRODUCE.
– A.K.A. “SURVIVAL OF THE FITTEST”

• POPULATION – GROUP OF
INDIVIDUALS OF SAME SPECIES
THAT INTERBREED
• GENE POOL – COMMON GROUP OF
ALL GENES PRESENT IN A
POPULATION

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 dimorphism: secondary sex characteristic distinction
• Sexual selection: selection towards secondary sex characteristics that leads to sexual dimorphism

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

Depends on how many genes control that trait

Single-Gene vs. Polygenic Traits
Single-Gene:
2 Distinct Phenotypes
Polygenic:
Many Phenotypes
(EG: tongue rolling)

Single Gene
Traits
Allele Frequencies
Natural Selection 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

• THE FORMATION OF NEW SPECIES
• AS NEW SPECIES EVOVLVE,
POPULATIONS BECOME
REPRODUCTIVELY ISOLATED
• REPRODUCTIVE ISOLATION –
MEMEBERS OF 2 POPULATIONS
CANNOT INTERBREED & PRODUCE
FERTILE OFFSPRING.

• 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.

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.

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.

An example of adaptive radiation – these species all diverged from a common ancestor (founder species)
FOUNDER SPECIES

• 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.

1.
Fossil Record
2.
Geographic Distribution of Living
Species
3.
Homologous Body structures
4.
Similarities in Embryology

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

Sugar
Glider
Marsupial Mammals
Convergent
Evolution and
Analogous
Structures
Flying
Squirrel
Placental mammals
Mammalia
Rat like common ancestor

 How did life arise on the big blue planet??
 Scientists attempt to answer this question scientifically.

• 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

• 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

 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.

 Earth was Hot!!
 Little or no oxygen
 Gasses in atmosphere:
 Hydrogen cyanide (poison to you!)
 Hydrogen sulfide
 Carbon dioxide
 Carbon monoxide
 Nitrogen
 water

 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

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

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
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
Endosymbiotic theory
 eukaryotic cells arose from living communities formed by prokaryotic organisms
 Ancient prokaryotes entered primitive eukaryotic cells and remained there as organelles