Reproduction Advantageous Advantageous traits traits must must be be passed passed to to progeny progeny Ability Ability to to pass pass on
on the the genotype genotype to to the the next next generation generation is is the the measure measure of of success success Biological Change Over
Time Microevolution Macroevolution Changes Change with in species Well defined mechanism Easily observed Based on selection
from one species to another Undefined mechanism Interpretation of: Cladistics Fossil record Geological data Microevolutionary Processes Drive a population away from genetic equilibrium
Small-scale changes in allele frequencies brought about by: Natural selection Gene flow Genetic drift Microevolution Genetics Microevolution
changes a population not individuals Traits in a population vary among individuals Microevolution is change in frequency of traits Natural Selection Reproductive success
for winning phenotypes Acts directly on phenotypes and indirectly on genotypes The first changed individual has no advantage The Gene Pool All of the genes in the population Genetic resource that
is shared (in theory) by all members of population Phenotype Variation Two copies of each gene (2 alleles)
Inherit different allele combinations Different combinations= different phenotypes Inherit genotype, NOT phenotypes Variation is inherited Genotypes, Phenotypes and Environmental Effects Himalayan rabbit experiment Pluck hare 2. Grow hair with cold pack Rabbits share genotype but phenotype is dependent on environmental conditions 1.
Fig. 10.18, p. 166 Genetic Equilibrium Allele frequencies at a locus are not changing 5 Rules for Equilibrium 1. 2. 3. 4. 5. No mutation
No immigration/ emigration Gene doesnt affect survival or reproduction Large population Random mating Interprete d No Variation No Variation No selection No selection No selection What happens when the rules are broken?
Rule #1 No Mutation Biological information changes Each gene has own mutation rate What determines rates? Effect of mutations on selection
Lethal Neutral Advantageous Variation in the gene pool? 1. Recombination 2. 5. Meiosis II (haploid germ cells)
Fertilization 4. Crossing over at meiosis I Independent assortment 3. Reorganizing Information Haploid + haploid = diploid
Changes in chromosome number or structure Mutations Changing Information Variation Eastern bluebird Western bluebird Mountain bluebird Rule #2 No
Immigration Immigration from a separate, segregated populations New variation Alleles Mutations Effects of immigration Shifts allele frequency Introduces new mutations through breeding
Gene Flow Physical flow of alleles into a population Tends to keep the gene pools of populations similar Counters the differences between two populations that result from mutation, natural selection, and genetic drift Rule #3 Survival or
Reproductive Advantage What does selection do for a population? Survival advantage or Reproductive advantage 1. 2. 3. 4. 5.
Pillars of Natural Selection Individuals of all populations have the capacity to produce more offspring than the environment is able to support, so individuals must compete for resources. Individuals of a population vary in size, form, and other traits. The variant forms of a trait may be more or less adaptive under prevailing conditions. When a form of a trait is adaptive under prevailing conditions, and when it has a heritable basis, its bearers tend to survive and reproduce more frequently than individuals with less adaptive forms of the trait. Over generations, the adaptive version becomes more common in the population. Natural selection is the result of differences in survival and reproduction among individuals of a population that differ from one another in one or more traits.
Natural selection results in modifications of traits within a line of descent. Over time, it may bring about the evolution of a new species, with an array of traits uniquely its own. Basics of Natural Selection Capacity and Competition All populations have the capacity to increase in numbers No population can increase indefinitely
Eventually, the individuals of a population will end up competing for resources Basics of Natural Selection Capacity and Competition The alleles that produce the most successful phenotypes will increase in the population Less successful alleles will
become less common Change leads to increased fitness Increased adaptation to a specific environment Results of Natural Selection Three possible outcomes: Directional selection Decreases variation in favor of an extreme. Stabilizing selection Selects most average/ common form of a
trait Disruptive selection Selects against intermediate forms Allele frequencies shift in one direction Number of individuals in the population Number of individuals in the population
Range of values for the trait at time 1 Range of values for the trait at time 2 Number of individuals in the population Directional Selection Range of values for the trait at time 3 Microevolution: Any change below the level of species: change in the base pair sequence of DNA or RNA
A gene frequency within a population or a species allelic effects on the form, or phenotype, of organisms that make up that population or species. Industrial Melanism Intermediate forms are favored and extremes are eliminated Number of individuals in the population
Stabilizing Selection Range of values for the trait at time 1 Range of values for the trait at time 2 Range of values for the trait at time 3 Resistance Chemical kills Antibiotic susceptible Resistance individuals Bacteria Resistant individuals
Antiviral Resistance survive HIV If resistance is Pesticide heritable, following generations exhibit Resistance the same trait. Insects Example: Pesticide Resistance Evolution in Action The DDT Paradigm Preadapted to
survive 99% Non-resistant die Spray Pesticide 100% resistant survive Spray with an Insecticide Second generation Second generation survivors Spray with an Insecticide
Third generation Third generation survivors Mutation rate = 1 x 10-4 100 butterflies or 1 in 10,000 1 million butterflies Beneficial mutation = 1 x 10-9 or 1 in
1,000,000,000 Insects Evolve at a High Rate Breeding super-bugs in the home? -Antibiotic resistance -Food safety -Bioterrorism -GMO foods Forms at both
ends of the range of variation are favored Intermediate forms are selected against Number of individuals Number of individuals in the population in the population Range of values for the trait at time 1 Range of values for the trait at time 2
Number of individuals in the population Disruptive Selection Range of values for the trait at time 3 Balanced Polymorphism Polymorphism - having many forms
Occurs when two or more alleles are maintained at frequencies greater than 1 percent Sexual Selection Selection favors certain secondary sexual characteristics Through nonrandom mating, alleles for preferred traits increase
Leads to increased sexual dimorphism Sickle-Cell Trait: Heterozygote Advantage Allele HbS causes sickle-cell anemia when heterozygous Heterozygotes are more resistant to
malaria than homozygotes Malaria case Sickle cell trait less than 1 in 1,600 1 in 400-1,600 1 in 180-400 1 in 100-180 1 in 64-100 more than 1 in 64 Rule #4 Large Population What happens if the population or allele frequency gets wacked?
Genetic Drift Random change in allele frequencies Most pronounced in small populations Sampling error - Fewer times an event occurs, greater the variance in outcome Fixation: one allele is established in a population Founder Effect
Small number of individuals start a new population Low probability that allele frequencies are the same as original population Effect is pronounced on isolated islands Bottleneck
A severe reduction in population size Causes pronounced drift Results All progeny will be very similar. Gene pool very shallow Rule #5 Random
Mating Inbreeding Nonrandom mating between related individuals Leads to increased homozygosity Can lower fitness when deleterious recessive alleles are expressed Genetic Equilibrium Allele frequencies at a locus are not
changing 5 Rules for Equilibrium 1. 2. 3. 4. 5. No mutation No immigration/ emigration Gene doesnt affect survival or reproduction Large population
Random mating Interprete d No Variation No Variation No selection No selection No selection Macroevolution and Speciation 1. Biological evolution is the theory that all living things are modified descendants of a common ancestor that lived in the
distant past, or descent with modification. 2. Evolution simply means change over time. Descent with modification occurs because all organisms within a single species are related through descent with modification Biological Species Concept Species are groups of interbreeding natural populations that are reproductively isolated from other such groups. Ernst Mayr
Morphology & Species Morphological traits may not be useful in distinguishing species Members of same species may appear different because of environmental conditions Morphology can vary with age and sex Different species can appear identical Variable Morphology Grown in water Grown
on land Isolation and Divergence Reproductive Isolation Cornerstone of the biological species concept Speciation is the attainment of reproductive isolation
Reproductive isolation arises as a by-product of genetic change Genetic Divergence Gradual accumulation of differences in the gene pools of populations Natural selection, genetic drift, and mutation can
Zygote is a fertilized egg Speciation Allopatric Different lands, (physical barrier) Sympatric Same lands (no physical or ecological barrier Parapatric Same border (small hybrid zone) Allopatric Effect Speciation in geographically isolated
populations Probably most common mechanism Some sort of barrier arises and prevents gene flow Effectiveness of barrier varies with species Extensive Divergence
Prevents Inbreeding Species separated by geographic barriers will diverge genetically If divergence is great enough it will prevent inbreeding even if the barrier later disappears Hawaiian Islands Volcanic origins, variety of habitats
Adaptive radiations: Honeycreepers - In absence of other bird species, they radiated to fill numerous niches Fruit flies (Drosophila) - 40% of fruit fly species are found in Hawaii Hawaiian Honeycreepers FOUNDER SPECIES Reproductive Isolation Cant allow gene flow Prezygotic Isolation
Ecological Isolation Temporal Isolation Behavioral Isolation Mechanical Isolation Gametic Mortality Postzygotic Isolation Zygotic mortality Hybrid inviability Hybrid sterility Zygote is a fertilized egg Speciation without a Barrier
Sympatric speciation Species forms within the home range of the parent species Parapatric speciation Neighboring populations become distinct species while maintaining contact along a common border Speciation by Polyploidy Change in chromosome number
(3n, 4n, etc.) Offspring with altered chromosome number cannot breed with parent population Common mechanism of speciation in flowering plants Possible Evolution of Wheat Triticum
monococcum (einkorn) 14AA Unknown species of wild wheat X 14BB T. turgidum (wild emmer) CROSS-FERTILIZATION, FOLLOWED BY A
SPONTANEOUS CHROMOSOME DOUBLING 14AB 28AABB X T. tauschii (a wild relative) 14DD T. aestivum
(one of the common bread wheats) 42AABBDD Parapatric Speciation Adjacent populations evolve into distinct species while maintaining contact along a common border
BULLOCKS ORIOLE BALTIMORE ORIOLE HYBRID ZONE Are We All Related? Are all species are related by descent? Do we share genetic connections that extend back in time to the first prototypical cell?
Patterns of Change in a Lineage Cladogenesis Branching pattern Lineage splits, isolated populations diverge Homology and morphology Anagenesis
No branching Changes occur within single lineage Gene flow throughout process Evolutionary Trees extinction (branch ended before present) new species branch point (a time of divergence,
speciation) a single lineage branch point (a time of divergence, speciation) a new species a single lineage dashed line
(only sketchy evidence of presumed evolutionary relationship) Gradual Model Speciation model in which species emerge through many small morphological changes that accumulate over a long time period
Fits well with evidence from certain lineages in fossil record Punctuation Model Speciation model in which most changes in morphology are compressed into brief period near onset of divergence Supported by fossil evidence in some lineages Adaptive Radiation
Burst of divergence Single lineage gives rise to many new species New species fill vacant adaptive zone Adaptive zone is way of life Adaptive Radiation
Extinction Irrevocable loss of a species Mass extinctions have played a major role in evolutionary history Fossil record shows 20 or more large-scale extinctions
Reduced diversity is followed by adaptive radiation Who Survives? Species survival is to some extent random Asteroids have repeatedly struck Earth destroying many lineages Changes in global temperature favor lineages that are widely distributed
extinction (branch ended before present) new species branch point (a time of divergence, speciation) a single lineage
branch point (a time of divergence, speciation) a new species a single lineage dashed line (only sketchy evidence of presumed evolutionary relationship)
Fig. 17.11 p. 268 Fig. 17.12 p. 269 Mechanism of Evolution Progeny Large Populations Genetic Variability Parental GenerationSelection Genetic Variability Mechanism of Evolution
Factors that cause change Mutations- new alleles Genetic Drift- unselected random change in allele frequencies Genetic Bottlenecks Founder effect Inbreeding Gene Flow- moving alleles with mating Natural Selection
ion changes allele frequencies in populations not indiv Struggle Struggle for for survival: survival: Different genetic makeup = different advantages Fitness = ability to pass on genotype to next generation = measure of success Endangered species - are they less fit? Survival: Selective forces - Competition for niches environment - Biotic forces: Disease - Abiotic forces eg. weather
Ability to adapt to human-derived habitats Survival of the fittest: Interplay of genetic variation vs selective forces Death before Reproduction Compete against siblings and others for food, mates, living space Survival: Natural Selection Result of evolutionary forces --animals capable of adapting (passing on their
genes to the next generation) Weeding out the slow and weak Survival: Preadaptation Already adapted to a condition not previously confronted with eg. coevolution of plants and arthropods Reproduction Reproduction must outweigh mortality -Predation -Parasitization -Disease -Lack of food -Lack of nesting sites -Environmental extremes
Over-reproduction Therefore...Evolution as a Scientific Theory is Well Supported by good science. - Adequately explains: Subspecies Groups: Races, Biotypes, etc. Resistance Adaptation within species Domestication of Animals, microbes and plants Evolution is a change from a no-howish untalkaboutable all-alikeness by continuous sticktogetherations and somethinglelsifications. --William James (1842-1910) American Psychologist
Glossary: Chapters 16, 17, 18 & 19 each have a glossary. In addition, the terms below will be helpful. Resistance: Pesticide use is a powerful selection pressure for changing the genetic makeup of a pest population. In the last decade, the number of weed species known to be resistant to herbicides rose from 48 to 270, and the number of plant pathogens resistant to fungicides grew from 100 to 150. Resistance to insecticides is very common. You can find the latest count on my website at http://whalonlab.msu.edu/resistance/rmdb. Resurgence: Pesticides often kill off natural enemies along with the pest. Without them, resistant populations experience unchecked growth Secondary Pests: Some potential pests which are normally kept to reasonable numbers by natural enemies become actual pests after their natural enemies are destroyed by pesticides. Mite outbreaks after pesticide applications are a classic example of this. Residues: Only a tiny portion of any pesticide application will contact the target
organism. The rest is often carried by water, wind and soil to non-target areas and organisms, affecting the health of human and wildlife populations. Variation from Sexual Recombination: -Diploidy -Mutation = changes in genetic sequence or chromosomal aberrations -Recruitment, genetic drift = migration
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