Evolution
Chapters 22-25
Evolution
Changes in populations, species, or groups of species.Variances of the frequency of heritable traits
that appear from one generation to the next.
2 Areas of Evolutionary Study
Microevolution Details of how
populations of organisms change.
Generation to Generation
New species origninate
Macroevolution Patters of change in
groups of related species.
Broad period of geologic time
Patterns determine phylogeny.
The evolutionary relationships among species and groups of species
Agree or Disagree
For each of the following statements decide if you agree that this is how evolution occurs or disagree.
After you have agreed or disagreed choose 2 agree statements and site examples and 2 disagree statements and site examples.
Lamarck
3 ideas for evolution:Use and Disuse Inheritance of acquired characteristicsNatural Transformation of species
Use and Disuse
How body parts of organisms can develop with increased usage, while unused parts weaken.
Inheritance of Acquired Characteristics
Described how body features acquired during the lifetime of an organism could be passed on to offspring.
Natural Transformation of Species
Organisms produced offspring with changes, transforming each subsequent generation into a slightly different form toward some ultimate higher order of complexity.
Species did not become extinct nor did they split and change into two or more species.
Evidence for Evolution
PaleontologyBiogeographyEmbryologyComparative AnatomyMolecular Biology
overproductioncompetitionvariation
adaptationNatural
Selectionspeciation
•More organisms are born than needed to maintain the population
competitionvariation
adaptationNatural
Selectionspeciation
Organisms compete for limited natural resources such as food, water, shelter and space.
variationadaptation
Natural Selectionspeciation
Organisms within a population vary. Variation is heritable.
adaptationNatural
Selectionspeciation
Any inherited trait that increases the chances of survival. Fitness is determined by the environment.
Natural Selectionspeciation
•Individuals with favorable variations (adaptations) are more likely to survive and pass on these traits to their offspring
• “Survival of the Fittest”
Evolution and Speciation
•Favorable variations (adaptations) gradually accumulate and unfavorable variations disappear over many generations
•Eventually this leads to a new species
4 Different types of Selection
Stabilizing SelectionDisruptive SelectionDirectional SelectionSexual SelectionArtificial Selection
Sources of Variation
MutationsSexual ReproductionDiploidyOutbreedingBalanced Polymorphism
Mutations
Raw material for new variation.Invents new genes that were never in
the gene pool before.
Sexual Reproduction
Creates individuals with new allele frequencies.
Genetic Recombination- 3 eventsCrossing Over Independent Assortment of HomologuesRandom Joining of Gametes
Diploidy
The presence of 2 copies of each chromosome in a cell.
Recessive alleles are hidden in the gene pool.
Outbreeding
Mating of unrelated partners.Increases the possibility of mixing
different alleles and creating new combinations.
Balanced PolymorphismMaintenance of different phenotypes in a
population.Heterozygote Advantage
The heterozygote condition bears a greater selective advantage. (Sickle Cell in Africa)
Hybrid Vigor/ heterosisSuperior quality of offspring resulting from crosses
between 2 different inbred strains of plants. Frequency-dependent selection
Least common phenotypes have a selective advantage. Predator mimicking prey.
Causes of Changes in Allele Frequencies
Natural SelectionMutationsGene FlowGenetic DriftNonrandom Mating
Gene Flow
The introduction or removal of alleles from the population ImmigrationEmigration
Genetic Drift
A random increase or decrease of alleles.2 Types
Founder Effect Alleles in a group of migrating individuals are not the
same as that of the origin population.Bottleneck
Population undergoes a dramatic decrease in size due to a natural catastrophe.
Nonrandom Mating
Individuals choose mates based upon their particular traits. InbreedingSexual Selection
How do we know evolution is occuring?
Hardy-Weinberg5 Conditions for Hardy-Weinberg
Equilibrium (evolution is not happening)All traits are selectively neutralMutations do no occurNo gene flowNo genetic driftRandom mating
Genetic Equilibrium Determination
Allele frequencies for each allelep is for the dominant alleleq is for the recessive allele
Frequency of homozygotesp2 is for the homozygous dominantq2 is for the homozygous recessive
Frequency of heterozygotespq + qp = 2pq
Equations
p + q= 1p2 + 2pq + q2 = 1
Example Problem
Suppose a plant population consists of 84% plants with red flowers and 16% with white flowers. Assume the red allele (R) is dominant to the white allele (r).
Do Hardy-Weinberg conditions meet any population?
NO!Why bother learning it?
Starting pointFurther investigation as to which condition is
being violatedMechanisms of evolution
Speciation
SpeciesSpeciation
The formation of a new species by one of 4 processes
AllopatricSympatricSympatric by PolyploidyAdaptive Ratiation
Allopatric Speciation
Population is divided by a geographic barrier.
Barrier creates isolation of breeding.Species continue to evolve by natural
selection (if environments are different), mutation, genetic drift.
Sympatric Speciation
The formation of a species without the presence of a geographic barrier.Balanced Polymorphism
Camouflage and MimicryHybridization
Sympatric Speciation by Polyploidy
The posession of more than the normal two sets of chromosomes (2n).
Polyploidy occurs as a result of non-disjunction of all chromosomes during meiosis.
A tetraploid can occur when two diploid gametes come together.
Reproductive Isolation thus speciation
Adaptive Radiation
Rapid evolution from a single speciesAdapts to geographic or ecological
conditions.Darwin’s Finches
Maintaining Reproductive Isolation
Necessary for speciationPrezygotic Isolating MechanismsPostzygotic Isolating Mechanisms
Prezygotic Isolating Mechanisms
Habitat IsolationTemporal IsolationBehavioral IsolationMechanical IsolationGametic Isolation
Postzygotic Isolating Mechanisms
Hybrid InviabilityHybrid SterilityHybrid Breakdown
Patterns of Microevlution
Divergent EvolutionConvergent EvolutionParallel EvolutionCoevolution
JigsawGroups of 4, 1-2 sentence summary.Picture or graph of evolution
Patterns of Macroevolution
Phyletic GradualismPunctuated Equilibrium
Phyletic Gradualism
Gradual Accumulation of small changes.
Fossil evidence provides snapshots of the evolutionary process.
Punctuated Equilibrium
Long periods of no evolution “stasis” followed by quick bursts of evolution.
The Earth and its atmosphere formed.
Consisted of CO, Carbon dioxide, hydrogen gas, nitrogen gas, water, sulfur, and hydrochloric acid.
Little or no oxygen gas.
The primordial seas formed
The earth cooled, gases condensed to produce seas consisting of water and minerals.
Complex molecules were synthesized.
Miller-Urey Experiment
Oranic molecules were formed from inorganic molecules with help from energy.
Polymers and self-replicating molecules were synthesized.
Monomers combined to form polymers.Proteinoids
Abiotically produced polypeptides
Organic molecules were concentrated and isolated into protobionts.
ProtobiontsCell precursors.Able to carry out chemical processesNot able to reproduce.
Microspheres and coacervates
Primitive heterotrophic prokaryotes formed.
Heterotrophs formed to take in materials.Natural selection
Primitive autotrophic prokaryotes were formed.
Mutation for an autotroph to be formed.Produces oxygen as a product of
chemical processes.
Oxygen and the ozone layer formed and abiotic chemical evolution ended.
Oxygen released in the atmosphere.Ozone layer made.UV light was filtered.Major source of energy was eliminated.
Eukaryotes formed
Endosymbiotic Theory