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Evolution (The Origin of Species (Hybrid: Offspring from 2 dif. species…

- - - - 3 pop. of species are connected
      - Barrier is established
      - One pop. diverges w other 2 pop.
      - Gene flow is re-established in hybrid zone
      - Reinforcement: Strengthening of barriers and hybrids cease to be formed
      - Fusion: Weakening of barriers, species fuse
      - Stability: Hybrid production continues
  - - - Biological Species Concept: Organisms that can reproduce and have fertile offspring is a species
      - Morphologic Species Concept: Distinguishes species by structural features
      - Ecological Species Concept: Environment they live in and how they interact w/ nonliving and living
    - - Prezygotic Barrier: Before Fertilization
        
        Habitat Isolation: Same species in same area but not same place therefore don't mate
        
        Temporal Isolation: Same species mating at different times
        
        Behavioral Isolation: No mate recognition (courtship rituals)
        
        Mechanical Isolation: Mating is attempted but because of physical differences it is unsuccessful (snails genital openings aren't aligned)
        
        Gametic Isolation: Can have sex but recognition proteins don't recognize sperm therefore cannot produce offspring
      - Postzygotic Barrier: After fertilization
        
        Reduced Hybrid Viability: Offspring are impaired or don't survive
        
        Reduced Hybrid Fertility: Offspring aren't fertile
        
        Hybrid Breakdown: 1st generation is viable and fertile but 2nd generation is sterile
  - - - Geographic Isolation causes allopatric speciation
      - (Darwin's finches)
      - Separated gene pools diverge and different mutations arise
      - Reproductive isolation increases as geographic distance increases
    - - (squirrels from Grand Canyon)
      - Occurs if gene flow is reduced by polyploidy, sexual selection, and habitat differentiation)
      - Less common than allopatric speciation
    - - Alloploidy: Dif. set of chromosomes from a dif. species
      - Autoploidy: 2+ sets of chromosomes from single species
      - Nondisjunction during mitosis or meiosis causes polyploidy
      - More common in plants b/c less of a problem
- - - - Populations Vary
      - Overpopulation (more babies than adults)
      - Environment couldn't support babies so some died and the ones that survived reproduced
      - Good characteristics live
    - - Individuals w/ favorable traits reproduce more
      - Populations shift depending on the environment
    - - Artificial Selection: Humans select + breed those w/ desirable traits
      - Microevolution: Evolutionary changes in populations
      - Macroevolution: Pattern of evolution above species level
      - Geological Strata: Superimposed layers of rock
  - - - Soapberry bug's beak lengths were similar to the depth the seeds are
      - When species are introduced to a new environment, natural selection would favor those with traits suited to the environment
      - Certain strains of Staphylococcus aureus became resistant to the antibiotics
    - - Homology is the similarity resulting from a common ancestor (forelimbs of mammals are similar)
      - Convergent Evolution Distantly related organisms resemble one another b/c of the environment they share
        
        Homologous: Similar structure but different lineage
        
        Analogous: Similar function but same species
      - Vestigal Structures are remnants of a structure that use to be of function but no longer is
      - All life forms have almost the same genetic code suggesting that all species descended from a common ancestor (LUCA)
    - - Shows a difference between present day and past organisms
      - Incomplete and doesn't record newer species or trait manifestations
      - Constantly being altered because there is always new information
      - Shows a pattern that those with favorable traits survive and reproduce
    - - Influenced by continental drift (Pangea)
      - Use our understanding of evolution and continental drift to predict where fossils of organisms can be found
      - Islands usually have organisms that are ENDEMIC (found nowhere else in the world)
- - - - Some variations are "either-or" whereas others vary
      - Certain genetic variations aren't important because it doesn't affect the chance of survival
      - Some phenotypic variation doesn't result from genetic differences
  - - - Organisms in a population show variations in their trains that are better suited for the environment produce more offspring than those that don't
      - Adaptive Evolution: Traits that enhance survival or reproduction tend to increase in frequency over time
      - Selection results in alleles being passed to the next gen. in proportions that differ from those in present gen.
    - - Can lead to the loss of an allele in the gene pool
      - Caused by chance events associated with survival and reproduction
      - Founder Effect: Few individuals are isolated + smaller group establishes new pop. + gene pool is different than larger group
        
        High frequency of certain inherited disorders
      - Bottleneck Effect: Drop in pop. b/c of environment changes
        
        Certain alleles more common than others and those will be passed on
        
        Less genetic variation
      - Significant in smaller populations
    - - Genes from another population being introduced can change the allele frequencies in the next pop.
      - Affect how well pop. are adapted to environment
      - Gene flow tends to reduce genetic differences between pop. (can result in 2 pop. becoming 1)
      - Can improve ability of pop. to adapt to environment
  - - - Directional Selection: Populations shift and favor one extreme (shifts pop. frequency curve) common when pop. migrates
      - Disruptive Selection: Conditions favor both extremes (ends up w/ 2 pop.)
      - Stabilizing Selection: Favors intermediate (extremes are weeded out)
      - Balancing Selection: Natural selection maintains 2+ phenotypic traits
    - - Sexual Selection: Ind. w/ certain inherited characteristics that are. desirable are more likely to reproduce
      - Sexual Dimorphism: Result of sexual selection w/ difference in secondary sexual characteristics between males/females
      - Intrasexual Selection: Direct competition among individuals
      - Intersexual Selection: One sex is choosy in selecting mate
      - Frequency-dependent Selection: Fitness of phenotype depends on how common it is