General Biology 2

• Taxonomy


  The science of describing, identifying, naming, and classifying organisms
• Taxonomy


  • It takes into account how organisms are related, but it does not totally reflect evolutionary relationships
• Taxonomic classification


  Groups organisms according to their relatedness
• Taxonomic classification (Hierarchy)


  Organisms are classified based on hierarchy
• Taxonomic traits


  Characters used to classify organisms according to their taxonomic groups. It is very important in quantifying the degree or relatedness of species with one another.
• Ancestral traits


  Evolutionary traits that are homologous within groups of organisms
• Ancestral traits

  The presence of jaws in fish, bird, rat and bat
• Derived traits


  Characters that are present in a species but absent in their ancestor
• Morphological traits


  The set of physical features of living organisms, both external and internal
• Developmental traits


  The set of developmental features that can be used for the classification of organisms, such as embryonic development
• Physiological traits


  The functional features of the structures
• Genetic traits


  Specific sequences of the DNA molecule in organisms
• Mendel, Johann (Gregor)


  Discovered how characteristics are passed down from one generation to the next — namely, dominant and recessive traits
• Law of independent assortment


  Genes for different traits can segregate independently during the formation of gametes
• Reproductive isolation

  • Prezygotic (barriers that prevent fertilization)
  • Postzygotic (barriers that occur after zygote formation such as organisms that die as embryos or those that are born sterile)
• Dichotomous key


  Designed to distinguish the differences among a set of organisms, separating into various categories based on physical characteristics until there are only two species remaining
• Dominant traits


  Those which are more likely to be inherited due to their stronger allele expression, typically passed vertically from parent to child where both are affected
• Recessive traits


  Traits that are expressed only when genotype is homozygous, and tend to be masked by other inherited traits, yet persist in a population among heterozygous genotypes