Chapter 5: Evolution

• Biological diversity is usually a sign of a healthy ecosystem
• When an ecosystem is biologically diverse, there is a higher chance that some organisms will survive changes in the ecosystem that arise
• Levels of biological diversity

  • Species Diversity
  • Genetic diversity
• Species Diversity


  Describes the number of different species able to successfully mate and produce viable offspring
• Species


  Communities of individuals that can interbreed successfully
• Two creatures that can’t interbreed, even if they resemble each other, must belong to different species
• Example of different species

  • Lions and tigers
• Lions and tigers are different species but can be artificially interbred, making Ligers and Tigons. They are generally sterile and short-lived (evolutionary dead-end)
• Genetic diversity


  The amount of variation in inherited traits between individuals of the same species
• In the wild, there are less noticeable differences between the same species
• Taxonomy


  The science of classification according to the inferred (presumed) relationships among organisms
• Biological classification systems have two main purposes: identifying organisms and providing a basis for recognizing natural groupings of living things
• Classification systems are artificial, developed by scientists to deal with diversity of life and to represent relationships among organisms
• Binomial Nomenclature is a method of naming organisms by using two names: the genus name and the species name. Scientific names are italicized
• Genus


  The first part of a binomial name; includes several species. Always capitalized, can be written alone
• Species


  A group of organisms that look alike and can interbreed under natural conditions to produce fertile offspring. Never used alone
• Names are based on an organism’s physical and structural features or a characteristic (colour, habitat)
• Linnaeus believed that more common features among organisms = closer relationship
• The two-part name uses Latin (and sometimes Greek) words
• Example: Castor canadensis. Castor is the Genus, meaning “Beaver”. Canadensis is the Species, meaning “from Canada”
• Levels of Classification


  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• For a simple abbreviation, use “King Philip Cry Out For Goodness Sake!”
• Protista is a kingdom originally proposed for all unicellular organisms such as the amoeba. More recently, multicellular algae have been added to the kingdom
• Monera is a kingdom that includes organisms that lack a true nucleus
• Five Kingdom-System proposed by Robert Whittaker in 1969 consists of Plantae, Animalia, Protista, Monera, Fungi
• Archaebacteria is a kingdom consisting of prokaryotic microorganisms distinct from eubacteria that possess a cell wall not containing peptidoglycan and that live in harsh environments such as salt lakes and thermal vents
• Eubacteria is a kingdom consisting of prokaryotic microorganisms that possess a peptidoglycan cell wall
• Six-Kingdom System proposed by Carl Wose and his colleagues in the 1970s consists of Eubacteria, Archaebacteria, Protista, Fungi, Plantae, Animalia
• Many microbiologists believe that the traditional kingdom classification systems should be replaced by a three-domain system that better shows the evolutionary history of life. This separates all of the Eukaryotes from the Eubacteria and Archaebacteria, which genetically are very different from each other
• Kingdoms


  • Archaebacteria
  • Protista
  • Fungi
  • Plantae
  • Animalia
• Phylogeny


  The history of the evolution of a species or a group of organisms
• Phylogeny


  Relationships shown in a phylogenetic tree starting from the most ancestral form, showing branchings that lead to all of its descendants
• Things that can fossilize

  • Bones
  • Burrows
  • Footprints
  • Chemical remains
• Living species and their closely related fossils are typically located in the same region
• Organisms generally become more complex over time
• Fossil evidence shows a systematic progression from very simple organisms to species of ever-increasing complexity
• Modern paleontologists can estimate accurate ages for fossils by comparing the amount of the original element and the amount of the new element and knowing the half-life
• Half-Life


  The amount of time it takes for half of a sample of the isotope to decay
• Radiometric Dating


  Technique used to determine the age of a rock or fossil by measuring the rate of decay of radioactive isotopes
• Radiometrically dating one isotope is unreliable, so data from a variety of isotopes is used