bio lab exam

• natural selection


  those individuals with advantageous traits survive better and therefore live to reproduce more, passing those traits on to the next generation
• natural selection leads to adaptation to the environment
• genetic drift


  random change in allele frequencies and thus the traits they encode
• population bottleneck


  a type of genetic drift where a large natural event causes high mortality rates, decreasing the types of alleles available
• founder effect


  a type of genetic drift, in which a new population is founded in a geographically distinct region
• genetic drift is not adaptive but still can cause evolution
• Conditions for Hardy-Weinberg equilibrium:

  • natural selection must not be occurring
  • no migration must be occurring
  • no mutation must be occurring
  • mating within population must be random
  • the population must be sufficiently large
• phylogenetic tree nodes


  common ancestor species
• phylogenetic tree traits


  features that are proposed to have evolved at the time shown
• phylogenetic tree extant (living) species

  shown at end of lines
• monophyletic group


  includes common ancestor and all its descendants
• paraphyletic group


  includes common ancestor but not all its descendants
• polyphyletic group


  does not include common ancestor
• derived character


  a trait found in a group that is not found in their ancestral group
• homoplasy


  a character trait shared between two groups that is not inherited from their common ancestor
• synapomorphy


  a trait that is derived from the most recent common ancestor, found in all its descendants
• phylum porifera


  sponges
• phylum porifera traits:

  • no true tissues
  • no symmetry
  • acoelomate (no body cavity)
• phylum cnidaria


  jellyfish, corals, anemones
• phylum cnidaria traits:

  • ectoderm and endoderm tissues
  • radial symmetry
  • acoelomate (no body cavity)
  • have tentacles with stinging cells called nematocysts
• phylum platyhelminthes


  flatworms (planaria, tapeworm, etc)
• phylum platyhelminthes traits:

  • ectoderm, endoderm and mesoderm
  • bilateral symmetry
  • acoelomate (no body cavity)
  • protostome development
• phylum nematoda


  roundworms
• phylum nematoda traits:

  • ectoderm, endoderm, and mesoderm (triploblastic)
  • bilateral symmetry
  • pseudocoelomate
  • protostome development
• phylum annelida


  segmented worms (earthworms, leeches)
• phylum annelida traits:

  • triploblastic
  • bilateral symmetry
  • coelomate
  • protostome
• phylum mollusca


  clams, mussels, squid, octopus, snails, slugs, etc
• phylum mollusca traits:

  • triploblastic
  • bilateral symmetry
  • coelomate
  • protostome (blastopore develops in mouth)
  • have mantle and muscular foot
• phylum arthropoda


  insects, spiders, scorpions, lobster, crab, shrimp, etc
• phylum arthropoda traits:

  • triploblastic
  • bilateral symmetry
  • coelomate
  • protostome
  • have jointed appendages, chitinous exoskeleton
• phylum echinodermata


  sea stars, sea urchins, sea cucumbers, etc
• phylum echinodermata traits:

  • triploblastic
  • bilateral and secondary pentaradial symmetry
  • coelomate
  • dueterostome
  • have spiny skin with endoskeleton, water vascular system
• diploblastic


  have ectoderm and endoderm tissues
• triploblastic


  have endoderm, mesoderm, and ectoderm tissues
• acoelomate


  no true body cavity
• pseudocoelomate


  body cavity not entirely lined by mesoderm
• coelomate


  true body cavity (coelom)
• protostome


  blastopore develops into mouth
• deuterostome


  blastopore develops into anus
• cephalochordata (invertebrates)

  • lancelets
  • notochord extends to front of head
  • all 4 chordate characteristics in adults