Text Chapter 8: Evolution and Natural Selection Flashcards
Observations that Led Darwin to Form his Theory of Evolution
- living organisms resemble extinct fossil organisms
- progressive changes from simpler to more complex organisms can be seen in the fossil record
- different island species resemble each other
- island populations resemble those on nearby islands
- lands with similar climates have unrelated plants and animals
- plants and animals of each continent are distinctive
Observations Reached in the Flowchart of Evolutionary Reasoning
- potential for rapid reproduction
- relatively constant resources and population over time
- variability in structures and behaviors
- some variability is inherited
Conclusions Reached in the Flowchart of Evolutionary Reasoning
- competition for survival and rapid reproduction
- natural selection- on average, the fittest organisms leave the most offspring
- evolution- the genetic makeup of the population changes over time driven by natural selection
Conclusions Reached in the Flowchart of Evolutionary Reasoning
- competition for survival and rapid reproduction
- natural selection- on average, the fittest organisms leave the most offspring
- evolution- the genetic makeup of the population changes over time driven by natural selection
Adaptation
a trait that makes a species survival more likely
Evolution
a change in the characteristics of organisms over time
Natural Selection
the mechanism for evolution, the fittest organism survive
Three Conditions Required for Natural Selection
- variations for a trait- different versions of a trait are found in a population
- heritability- variations on the trait are passed from parents to offspring
- differential reproductive success- individuals best adapted to the environment leave the most offspring
Three Conditions Required for Natural Selection
- variations for a trait- different versions of a trait are found in a population
- heritability- variations on the trait are passed from parents to offspring
- differential reproductive success- individuals best adapted to the environment leave the most offspring
Analogous Structures
superficially similar, do not show a common origin
Homologous Structures
same evolutionary origin despite differences in function
Directional Selection
increases one extreme
Stabilizing Selection
eliminates both extremes
Disruptive Selection
increases both extremes
Disruptive Selection
increases both extremes
Evidence for Evolution after Darwin
- fossil record
- geological (sufficient time for evolution based on age of earth)
- comparative anatomy (analogous, homologous, vestigial structures)
- embryology (similar embryonic patterns of development)
- biochemistry (molecular similarities between different organisms)
- genetics (mutation generates diversity, meiosis and fertilization generate new combinations due to crossing over, alternate patterns of chromosome segregation, unique genotype of fertilizing sperm combined with unique genotype of egg)
Evidence for Evolution after Darwin
- fossil record
- geological (sufficient time for evolution based on age of earth)
- comparative anatomy (analogous, homologous, vestigial structures)
- embryology (similar embryonic patterns of development)
- biochemistry (molecular similarities between different organisms)
- genetics (mutation generates diversity, meiosis and fertilization generate new combinations due to crossing over, alternate patterns of chromosome segregation, unique genotype of fertilizing sperm combined with unique genotype of egg)
Ways in which Scientists can Observe Natural Selection in Action Today
artificial selection (dog breeds) -insecticide resistance (in western corn rootworm larvae)
Major Sources of Genetic Variability
-mutation generates diversity
-meiosis and fertilization generate new combinations due to:
crossing over, alternate patterns of chromosome segregation, unique genotype of fertilizing sperm combined with unique genotype of egg
Describe how Natural Selection Contributes to Evolution
the fittest offspring survive, over time makes organisms best suited to their environment
Describe how Natural Selection Contributes to Evolution
the fittest offspring survive, over time makes organisms best suited to their environment
Mutation
an alteration in the base-pair sequence in the DNA of an individual’s gamete- producing cells that changes an allele’s frequency
Genetic Drift
a random change in allele frequencies, unrelated to any allele’s influence on reproductive success
Migration (gene flow)
a change in allele frequencies caused by individuals moving in or out of a population
Natural Selection
a change in allele frequencies that occurs when individuals with one version of a heritable trait have greater reproductive success than individuals with a different version of the trait.
Describe the types of color and pattern adaptations that can arise as a result of natural selection
organisms adapt to camouflage to their environment to hide from predators, or become brightly colored to ward off predators
