Post on 04-Jan-2016
Changes in the genetic makeup of populations
Natural Selection1.Populations
tend to overproduce offspring.
Natural Selection
2. Genetic variation exists within populations
Natural Selection3. The best adapted organisms survive and reproduce in
greater numbers.
Natural Selection4. Subsequent generations
contain higher frequencies of adapted orgs.
Adaptation Inherited trait
Increases chance of survival/reproduction
Environment-specific
Natural SelectionThe environment determines success of traits
1.Overproduction2.Genetic variation3.Struggle for survival4.Differential reproduction
Natural Selection
Hardy-Weinberg Conditions
Hypothetical conditions that must exist in a population for no evolution to
occur.
Population CharacteristicsHinder Evolution(Hardy-Weinberg Conditions)
Infinitely Large
Random Mating
Equal Survival
Isolation
No mutations
Help Evolution(Natural Conditions)
Small Genetic Drift
Natural Selection
Natural Selection
Gene Flow
Mutations
POPULATION SIZE
MATING
VIABILITY
INTERACTION W/ OTHER POPS
DNA CHANGES
Genetic DriftRandom fluctuations in genetic makeup
Example: 2 red, 2 blue orgs seek shelter 50% survive. All are red Blues eliminated by chance (17%)
4 red, 4 blue head for shelter 50% survive. All are red Blues eliminated by chance (1.4%)
Genetic DriftBottleneck Effect
Catastrophe cuts pop size Decreased variety of traits Altered genetic makeup Genetic drift more likely
Founder Effect
Small group emigrates to new habitat
Gene Flow Introduction of new traits through immigration May be beneficial or insignificant New traits altered genetic makeup
Modes of Selection Stabilizing
Environment is stableInitially adaptive form
becoming more numerous from many generations of natural selection RANGE OF PHENOTYPES
MOST ADAPTIVE FORM
Modes of Selection Directional
Environment is changing (or has changed)
Formerly adaptive form is no longer adaptive
Pop evolves toward newly adaptive form
MOST ADAPTIVE FORM
RANGE OF PHENOTYPES
RANGE OF PHENOTYPES
Modes of Selection
Disruptive(Diversifying)
Intermediate form is undesirable and decreases in #
MOST ADAPTIVE
FORMS
MOST ADAPTIVE
FORMS
Evolution of the Ctukis Ctukis are creatures from a planet you’ve never
heard of. You will construct a ctuki out of a single 8½x11
sheet of paper.Do not add any materials.Put your names on the ctuki.Your ctuki must be able to asexually reproduce in class
(it should take no more than one minute).