Chapter 10

• Classification

  process of sorting living organisms into groups based on similar features they share
• Name the 8 taxonomic groups from biggest to smallest

  
  

  • domain do
  • kingdom keep
  • phylum plates
  • class clean
  • order or
  • family family
  • genus gets
  • species sick
• Define species

  
  

  • group of organisms that are able to reproduce to produce fertile offspring
• 2 parts of a binomial name

  • generic name - indicates genus - shared by close relatives

  • specific name - indicates species
• How should an organism's scientific name be written?

  • in italics (underline if handwritten) 

  • lowercase w exception of first letter of genus name which should be uppercase
• Advantage of binomial naming system

  
  

  • it's universal - an organisms binomial name is same everywhere in world
• Name the 5 kingdoms

  
  

  • prokaryotae (bacteria)
  • protoctista (unicellular eukaryotes)
  • fungi (e.g. yeasts, moulds, mushrooms)
  • plantae (plants)
  • animalia (animals)
• Reasons for classification

  • to identify species
  • to predict characteristics
  • to find evolutionary links
• General features of Protoctista

  • (mainly) unicellular
  • has nucleus & other membrane-bound organelles
  • some have chloroplast
  • nutrients acquired by photosynthesis, ingestion of other organisms or both - some parasitic
  • some sessile, others move by cilia, flagella
• General features of fungi

  • unicellular or multicellular
  • have nucleus & membrane-bound organelles & cell wall mainly composed of chitin
  • no chloroplasts
  • no mechanisms for locomotion
  • nutrients acquired by absorption - saprophytic feeders
• General features of Plantae

  • multicellular
  • have nucleus & other membrane-bound organelles - inc. chloroplasts & cell wall mainly composed of cellulose
  • nutrients acquired by photosynthesis - autotrophic feeders
  • most don't move
• General features of animalia

  • multicellular
  • nucleus & other membrane-bound organelles (no cell wall)
  • no chloroplasts
  • move w aid of cilia, flagella or contractile proteins
  • nutrients acquired by ingestion
• General features of prokaryotae

  • unicellular
  • no nucleus or membrane-bound organelles
  • no visible feeding mechanism - nutrients absorbed through cell wall or produced internally by photosynthesis
• What system did Wose propose?

  • Three Domain System
  • further level of classification at top of hierarchy
  • uses diffs in sequences of nucleotides in cells rRNA, cells membrane lipid structure & their sensitivy to antibiotics
• Name the 3 domains

  • archae
  • bacteria
  • eukarya
• Differences between each domain

  • eukarya - 80s ribosomes; RNA polymerase contains 12 proteins
  • archaea - 70s ribosomes; RNA polymerase contains 8-10 proteins
  • bacteria - 70s ribosomes; RNA polymerase contains 5 proteins
• Phylogeny

  • study of evolutionary relationships between organisms
• Phylogenetic trees

  • closer the branches, closer the relationship
  • earliest species found at base of tree, and most recent species found at tips of branches
  • branch length is proportional to time

  
• Advantages of phylogenetic classification

  • can be done without reference to Linnaean classification
  • produces a continuous tree whereas classification requires discrete taxonomical groups - scientisist not forced to put organisms into group they don't quite fit

  • heirarchal nature of Linnaean classification can be misleading as it iplies different groups within same rank are equivalent - e.g. cats and orchids are both families but 2 groups not comparable
• How did Charles Darwin develop theory of evolution?

  • Formed the initial theory of evolution by natural selection
  • Observed finches on the Galapagos Islands - slight differences between species on neighbouring islands indicated birds related but had developed different adaptations suited to their food sources
  • Studies of artificial selection by pigeon breeders enabled him to draw parallels with how natural selection works
  • Influenced by Charles Lyell's geological theories - fossils evidence of animals living millions of years ago and natural processes can result from gradual change & accumulations
• 3 sources that provide evidence for evolution

  • palaeontology
  • comparative anatomy
  • comparative biochemistry
• Evidence provided by palaeontology (fossils)

  • fossils of simple organisms tend to be found in the oldest rocks, whereas more complex organisms are found in more recent rocks
  • sequence organisms found match their ecological links to each other - e.g. plant fossils appear before animal (animals require plants to survive therefore evolved later)
  • similarities between diff fossil species reveal gradual anatomical changes over time
  • allow relationships between extinct & living organisms to be investigated
• Limitations of fossil record

  • not complete
  • many organisms decompose before they have chance to fossilised
  • conditions needed for fossils to form not often present
  • fossils destroyed by Earth's movements e.g. volcanoes
• What is comparative anatomy?

  • study of similarities and differences in the anatomy of different living species
• What is a homologous structure?

  • anatomical features have slight differences but same underlying structure
• Evidence provided by comparative anatomy

  • homologous structures provide evidence of divergent evolution - describes how from a common ancestor different species have evolved, each with a diff set of adaptive features
• What is comparative biochemistry?

  • study of similarities and differences in the proteins & other molecule that control life processes
• Evidence provided from comparative biochemistry

  • rate of mutations in DNA can be calculated - enables evolutionary relationships to be analysed
  • closer the relationship between 2 species, the fewer differences in their DNA base sequences
• What is interspecific variation?

  • variation between members of different species
  • e.g. mouse has 4 legs, teeth & fur whereas bird has 2 legs, 2 wings, a beak
• What is intraspecific variation?

  • differences between individuals in same species
  • e.g. people vary in height, eye colour, intelligence
• 2 factors causing variation

  • genetic material
  • environment
• Genetic causes of variation

  • alleles
  • mutations
  • meiosis
  • sexual reproduction
  • chance
• How do alleles introduce variation?

  • genes have different alleles
  • diff alleles produce diff effects
• How do mutations introduce variation?

  • changes to DNA sequence can lead to changes in proteins that are coded for
  • protein changes affect physical & metabolic characteristics
• How does meiosis introduce variation?

  • before nucleus divides and chromatids separate, the genetic material from the parents is 'mixed up' by independent assortment and crossing over
  • this leads to gametes of individual showing variation
• How does sexual production introduce variation?

  • offspring inherits genes from each of the 2 parents
  • each individual produced differs from the parents
• How does chance introduce variation?

  • during sexual reproduction it is a result of chance which 2 gametes combine to form a zygote
• How do species that undergo asexual reproduction gain genetic variation?

  • only as a result of DNA mutation
• Which organisms are more greatly affected by environmental variation?

  • plants - due to their lack of mobility
  • e.g. as plant can't move to gain sunlight it is more affected by environment than an animal which could move to another area to look for food/shelter
• What is a characteristic purely determined by environmental variation?

  • scarring