EES 106-02

Fossils

  • Trace fossils
    • tracks
    • trails
    • burrows
  • provides behavioral information about extinct animals
  • fossils provide iased view of life
    • not all organisms are preserved
      • rare
      • lack hard parts
    • not all skeletal material is preserved
      • scavengers
      • transport and abrasion
      • post burial alteration of rock
    • not all fossils are exposed at the surface
    • some form fossil fuels

moving from fossils to living organisms

  • we need a fundamental understanding of organism classification to understand past and present life
  • fossils help us understand organisms from the past and how these organisms may have contributed to their present day activities

taxonomic groups

  • six kingdoms
    • prokaryotes: cells doe not comtaina membrane bound nucleus
      • archaeobacteria
      • eubacteria
    • eukaryotes: cells have a nucleus
      • plantae
      • fungi
      • animalia
      • protista
  • taxa range from broad (phylum) to narrow (species)
    • phylum
    • class
    • order
    • Genus
    • species
      • group of individuals that can interbreed

taxonomic classification for humans

  • phylum – Chordata
  • Class – mammalia
  • order – primates
  • family – Hominidae
  • Genus – Homo
  • species – sapiens
  • phylogeny
    • “tree of life”
    • structure formed by branches of species
  • cluster into groups with similar traits, equivalent to taxa
    • genera
      • small clusters
  • clade
    • cluster of species that share a common ancestry
    • all species within each clade must be traceable to a common ancestor

traits in taxonomic groups

  • primitive traits
    • appear early in evolutionary history
    • hagfish group traits
  • derived traits
    • evolved later
    • present only in some subgroups
    • jaws, lungs, claws or nails, feather, fur and mammary glands

fossils used to trace ancestry

  • horse ancestry
    • detailed due to abundant fossil record
  • three clades – share common ancestry
  • all members of the modern horse family belong to Equus and originated in N. America

evolution

  • process by which particular forms of life give rise to other forms by way of genetic changes
    • macroevolution
    • microevolution

How does evolution work

  • macroevolution – origin of a new species, in which the span of human existence is too short for us to see
  • microevolution – adaptive changes occurring within an existing species
    • direct human intervention
    • manmade changes to environment
    • naturally – differing environmental conditions

most evolution occurs when a population is isolated from its parent population

  • ecology of an area
  • different behavior of similar species
  • reproductive incompatibility of closely related species
  • different mating seasons, and sterile hybrids

types of evolution

  • divergent
    • an interbreeding population that gives rise to a diverse group of descendants is called divergent evolution
  • parallel
    • modern anteaters evolved from very different ancestors to fill a similar ecologic niche (parallel evolution). this is the result of geographic isolation
  • convergent
    • marsupial and placental mammals are a good example of convergent evolution

Mendelian inheritance

  • traits within a species are controlled by genes
  • genes controlling the same trait that occur in different forms are called alleles
  • dominant color is brown (R), recessive color is non-brown (r)

genes in populations

  • microevolution – change in gene frequency
    • mutation – random errors in DNA replication
    • mixing with other populations
    • isolation of a small sub-population
    • non-random mating – formation of manes, antlers, bright plumage (sexual selection)
    • natural selection – survival of the fittest
  • macroevolution – changes brought about by natural selection operating on the variability of populations over long periods of time would lead to the divergence of a population to form a new species
    • speciation – branching off of new species from existing ones
    • isolation is necessary for speciation to occur
      • geographic separation
      • ecology – population occupies same area but different habitat
      • bahvior – elaborate courtships prevent mating
      • reproductive incompatibility
      • timing
      • nonviability of hybrids – usually sterile

Using fossils to tell time

  • looking at present organisms to understand past life
  • looking at fossils and their modern relatives
  • organism physiological and evolutionary development
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