ch18 Flashcards
Darwin’s Observation
Geographic distinction of organisms
Galápagos Islands (finches and tortoises)
Darwin vs Lamarck
Lamarck - giraffes stretched their necks from short to long
Darwin - both short and long necks, natural selection favored long necks (more resources)
Natural Selection
1) Organisms have heritable traits
2) Competition of resources
3) Individuals vary with reproductive success
4) Organisms may adapt with environmental change
Variation through genes
Competition, Fitness, and Adaptation
Fossil Evidence
Transitional species preserved
Anatomical Evidence
Homologous, Analogous, and Vestigial structures
Homologous structure
Inherited from common ancestor
Ex: Vertebrate forelimb
Analogous structure
Originated individually (over many times)
Ex: Wings
Vestigial structure
Important to ancestor and remains in derived species
Ex: Pelvic bone in whales and snakes
Biochemical evidence
All organisms have DNA
DNA -> RNA -> Protein
Biogeographical Evidence
Similar global strata
Evidence of Pangea
Misconceptions of Evolution
1) Evolution is just a theory
2) Individuals in a population evolve
3) Evolution is a theory tied to origin of life
4) Transitional fossils remain unknown
5) Organisms evolve on purpose
6) Random chance alone guides evolution
7) Evolution is not testable
8) Humans evolve directly from apes
Species Concept
Species - Latin for “kind”/”appearance”
Same “kind” of organism that may interbreed naturally and produce viable offspring
Limited to reproduction definition
Speciation
Formation of two species from one
(Allopatric or Sympatric)
Allopatric speciation
Geographic isolation between species and two species form
Sympatric speciation
Within the same area
Gene flow can occur or be disturbed
(Polyploidy, Autopolyploid, Allopolyploid, Sexual seletion, Habitat differentiation)
Polyploidy
more than 2 chromosome pairs
Autopolyploid
Cell division error creates a tetraploid cell
Yields new species
Allopolyploid
Interbreeding species
Hybrids often sterile
Sexual selection
Females select males and males differ by color
Habitat differentiation
Subpopulations that exploit different resources
Prezygotic Barriers
Habitat isolation
Temporal isolation
Behavioral isolation
Mechanical isolation
Gametic isolation
Habitat isolation
Two species in two habitats within the same area
Prevents mating
Temporal isolation
Seasonality of breeding
Prevents mating
Behavioral isolation
Courtship rituals performed by males
Prevent mating
Mechanical isolation
Mating attempted, but mismatched copulation
Prevents fertilization
Gametic isolation
Physical or biochemical barrier even when multiple eggs/sperms present
Prevents fertilization
Postzygotic Barrier
Fertilization has occurred
Reduced hybrid viability (low survival rate)
Reduced hybrid fertility (often sterile)
Hybrid breakdown - 1st generation sterile, but subsequent generations may not be
Hybrid Zones
Overlapping areas of two species that allow the two species to interbreed
Climate change shifts zones
Three possible outcomes (Reinforcement, Fusion, Stability)
Reinforcement
Strengthens reproductive barriers
Natural selection is the agent of change
Fusion
Weakening of reproductive barriers
Gene pool becomes more alike
Hybrids may further stress existing species
Stability
Continued formation of hybrid individuals and both species regularly enter hybrid zones
Narrow hybrid zone -> higher mating chances
Wide hybrid zone -> lower mating chances
Punctuated model
Short speciation period, prolonged stability, and abrupt extinction
Gradual model
Small, incremental changes over entire period and produces two species
