BIOL 117 Exam 2

Chapter 15

  • Define evolution
    • Evolution: the change in the genetic composition of a population over successive generations “Descent with Modification”
  • Explain the development of the theory of evolution
    • Developed by Darwin
    • Published On the Origin of Species by Means of Natural Selection
    • Charles Darwin’s work on evolution challenged established worldviews
    • Darwin proposed a mechanism for evolutionary change called Natural Selection
    • Darwin’s hypothesis for evolutionary change, after much testing, eventually became accepted as theory
    • Darwin made several observations that helped lead him to     believe that species evolve rather than remain fixed

     1. Fossils of extinct organisms resembled those of living        organisms 2. Patterns in the geographical distribution of organisms        suggested that organismal lineages change gradually as        individuals move into new habitats 3. Islands have diverse animals and plants that are related        to, yet different from, their mainland sources

  • Explain how natural selection can lead to evolution
    • Natural Selection = Mechanism for Evolution
    • Natural selection… aka “survival of the fittest” or “fit enough”
    • A mechanism for the more prolific reproduction of individuals with favorable traits that survive environmental change because of those traits.
    • This leads to evolutionary change, the trait becoming predominant within a population.
    • A mechanism of evolution -differential survival and reproduction of individuals within a population -due to differences in heritable traits -selected traits are most adapted to the environment (that can change!)
    • Natural selection is a process based on the     following observations:

     1. Organisms exhibit variation that can be passed from one        generation to the next—        that is, they have heritable variation. 2. Organisms compete for limited resources. 3. Individuals within a population        differ in terms of their reproductive success. 4. Organisms become adapted to conditions as the environment        changes.        “Nature selects which traits are adaptive to the local environment”

  • Provide examples of visible evidence of evolution
    • Peppered Moths
    • Variation in finch beaks
  • Explain the categorical bodies of evidence for the theory of evolution
    • Fossils
    • Similar Structures
    • Homologous structures – all contain the same sets of organized bones in similar ways
    • Embryological development (Ontogeny)
  • Explain why only heritable variation can be acted upon by natural selection
    • Organisms exhibit variation that can be passed from one generation to the next
    • Natural Selection favors heritable traits that enhance survival and reproduction

Chapter 16

  • Describe the agents of evolutionary change
    • populations and species evolve, individuals do not
    • 5 forces can cause changes to the frequency of genetic variation in a population, thus, enabling a population to evolve

  

  1. Mutations
  2. Natural selection
  3. Migration/Gene flow
  4. Nonrandom mating/Assortative      (sexual selection)
  5. Genetic drift
  • Determine the type of natural selection operating on a trait based on the change in phenotype distribution
    • mutations??
  • Assess the ways in which genetic variance affects the evolution of populations
    • genetic variance drives evolution
  • Compare stabilizing, directional, and diversifying/disruptive selection
    • Stabilizing selection: Selects against extreme phenotypes
    • Directional selection: Favored phenotype shifts in one direction
    • Disruptive selection: Selects against average phenotypes
  • List two examples of how diversity is maintained in populations
    • diversity is maintained in populations through…?
  • Explain how natural selection can lead to adaptive evolution
    • traits that can be passed down allow organisms to adapt to the environment better than other organisms of the same species. This enables better survival and reproduction compared with other members of the species, leading to evolution
  • Explain how evolution in populations is related to a change in allele frequencies
    • as organisms evolve, the allele frequencies are changed on a population level
  • List the five conditions necessary to maintain Hardy-Weinberg equilibrium
    • 1.The size of the population is very large or effectively infinite.

     2. Individuals mate with one another at random. 3. There is no mutation. 4. There is no immigration or emigration. 5. All alleles are replaced equally from generation to generation (natural selection is not occurring)

  • Use the Hardy Weinberg equation to calculate allelic and genotypic frequencies in a population
    • p+q=1
    • p^2+2pq+q^2=1

Chapter 17

  • Compare and contrast microevolution and macroevolution
    • macroevolution occurs at the species level or higher, microevolution occurs at population or lower
  • Explain the different ways that species are defined
    • Morphological: Based on analysis of one or more distinct physical diagnostic traits distinguishing one species from another
    • Biological: For sexually reproducing organisms, is a group of actually or potentially interbreeding individuals • There are exceptions to this rule : Hybrids
    • Phylogenetic: Compares differences in DNA sequences to identify a single ancestor for two or more different groups • Smallest set of interbreeding individuals that share a common ancestor
  • Define the modes of speciation and give examples of how it can happen
    • Speciation: the formation of two species from one original species
    • 2 modes:
    • Sympatric (sym- = "same"; -patric = "homeland") involves speciation occurring within a parent species, remaining in one location, No geographic separation
    • Allopatric (allo- = "other"; -patric = "homeland") involves geographic separation of populations from a parent species and subsequent evolution.
  • Identify and compare features of prezygotic and postzygotic reproductive isolation
    • prezygotic: prevent mating attempts or make it unlikely that fertilization will be successful.

     1. Habitat Isolation – species occupy different habitats 2. Temporal Isolation – each reproduces at a different time 3. Behavioral Isolation – courtship patterns for recognizing mates differ 4. Mechanical Isolation – incompatible animal genitalia or plant floral structures 5. Gamete Isolation – gametes that meet do not fuse to become a zygote

  • postzygotic: Prevent hybrid offspring from developing or breeding

     1. Hybrid Inviability – hybrid zygote is not viable and dies 2. Hybrid Sterility – hybrid zygote develops into a sterile adult

  • Explain how convergent evolution differs from other modes of evolution
    • convergent evolution occurs when a similar biological trait evolves in two unrelated species as a result of exposure to similar environments, results in analogous structures but does not indicate common ancestry
  • Distinguish between the gradual and the punctuated equilibrium models of evolution
    • gradual:
    • Evolution at the species level occurs gradually
    • Speciation occurs after populations become isolated
    • Each group continues its own evolutionary pathway
    • The gradualistic model suggests that it is difficult to indicate when speciation occurred
    • punctuated:
    • This model states that periods of equilibrium are punctuated by speciation
    • Species can appear quite suddenly
    • The assembly of species in the fossil record can be explained by periods of equilibrium interrupted by abrupt speciation
    • Some fossil species can be explained by the gradualistic model and others by the punctuated equilibrium model
      • Stabilizing selection can keep species in equilibrium for long periods

Chapter 18

  • Define LUCA
    • Last Universal Common Ancestor (LUCA) is common to all organisms that live, and have lived, on Earth since life began
  • List and describe the four stages of the origin of life
    • Stage 1: Organic monomers evolved from inorganic compounds (ex. Amino acids)
    • Stage 2: Organic monomers were joined to form organic polymers (ex. RNA, DNA, proteins)
    • Stage 3: Organic polymers became enclosed in plasma membranes to form protocells (protobionts)
    • Stage 4: Protobionts acquired the ability to self-replicate.
  • List and describe hypotheses for the origin of life
    • Iron-Sulfur World Hypothesis: It suggests organic molecules reacted with amino acids to form peptides in the presence of iron-nickel sulfides in thermal vents deep at ocean floor
    • Protein-First Hypothesis: Amino acids can polymerize in the presence of dry heat into proteinoids, Proteins came first, DNA genes came afterwards.
    • RNA-First Hypothesis: It suggests only RNA was needed to progress toward formation of the first cell or cells., RNA can act as both a substrate and an enzyme, Some viruses have only RNA genes, DNA genes would have come after RNA genes via reverse transcription
  • Explain endosymbiotic theory
    • Mitochondria were probably once free-living aerobic prokaryotes. → Chloroplasts were probably once free-living photosynthetic prokaryotes → A nucleated cell probably engulfed these prokaryotes that became various organelles
    • Mitochondria and chloroplasts are similar in size to bacteria
    • Mitochondria and chloroplasts have their own DNA and make some of their own proteins
    • Mitochondria and chloroplasts divide by binary fission
    • The outer membranes of mitochondria and chloroplasts differ
  • Explain how geology influenced the evolution of life
    • plate tectonics and continental drift affected what organisms were found where as well as habitats
    • Example: marsupials able to diversify with less competition, endemic to Americas and Australia
  • What are the roles of mass extinctions in the history of life
    • large losses of genetic diversity (allele frequency), less biodiversity

Chapter 19

  • Differentiate among taxonomy, classification, and systematic biology.
    • Taxonomy: formal system of classification, naming and grouping species
    • Systematics: field of study determining evolutionary relationships of organisms / species
    • Phylogeny/Cladogram: visual (graphical) representation of evolutionary relationships
  • Use the classification system in the correct order & Identify the levels of the classification hierarchy.
    • Kingdom, Phylum, Class, Order, Family, Genus, Species
  • Identify the genus and species of an organism from its scientific name
    • Genus species
  • List the three domains of life
    • Eukarya, Bacteria, Archaea
  • Summarize two characteristics that define each of the three domains.
    • Bacteria: unicellular, peptidoglycan cell wall
    • Eukarya: mostly multicellular, membrane bound organelles
    • Archaea: unicellular, cell wall no peptidoglycan
  • Discriminate between ancestral and derived traits.
    • Ancestral traits:
    • Present in all members of a group
    • Present in the common ancestor
    • Are not useful for determining the evolutionary relationships of an ancestor’s descendants
    • Derived traits (Synapomorphies):
    • Present in some members of a group, but absent in the common ancestor
    • Are the most important traits for clarifying evolutionary relationships
    • An opposable thumb, not present in the common ancestor of all mammals, is an ancestral trait of primates
  • List the types of traits that can be used to construct a phylogeny
    • Anatomical features
    • Behavior
    • DNA sequences