species and taxonomy

• • Courtship in animals is a behaviour that eventually results in mating and reproduction
• Courtship

  • It can be a very simple process that involves a small number of visual, chemical or auditory stimuli
  • It can also be a highly complex sequence of acts by two or more individuals, which are using several modes of communication
  • Many birds of paradise have intricate and impressive courtship rituals
  • Courtship can play a major role in species recognition
• Phylogenetic Classification

  • Taxonomy is the practice of biological classification
  • The phylogenetic classification system enables us to arrange species into groups based on their evolutionary origins and relationships
  • There is no overlap between groups and each group is called a taxon (plural taxa)
  • By grouping organisms into taxa it can make them easier to understand and remember
• • There are several different ranks or levels within the hierarchical classification system used in biology
  • Multiple smaller taxa can be put in the same larger taxa
• • The highest rank is the domain
  • Cell type has a major role in the classification of organisms into the three domains; but do not confuse cell types and domain
  • Prokaryotic cells are easily distinguishable in that they lack a nucleus
  • Eukaryotic cells have compartmentalised structures, with at least their genetic material segregated from the rest of the cell in a nucleus
• • Based upon molecular analysis of RNA genes in particular, scientists have realised that using cell type to classify organisms is insufficient, and that prokaryotes could be divided into two separate groups (domains)
  • The three domains are:
  • Archaea (prokaryotes)
  • Bacteria (prokaryotes)
  • Eukarya (eukaryotes)
• Archaea

  Organisms within this domain are sometimes referred to as the extremophile prokaryotes, archaea were first discovered living in extreme environments, but not all archaea do
• Archael cells


  • Have no nucleus (and so are prokaryotic)
  • Unique lipids being found in the membranes of their cells
  • No peptidoglycan in their cell walls
  • Ribosomal structure (particularly that of the small subunit) are more similar to the eukaryotic ribosome than that of the bacteria
  • Similar size range as bacteria (and in many ways metabolism is similar between the two groups)
  • DNA transcription is more similar to that of eukaryotes
• Archaea were initially classified as bacteria until several unique properties were discovered that separated them from known bacteria
• Bacteria

  • These are organisms that have prokaryotic cells which contain no nucleus
  • They vary in size over a wide range: the smallest are bigger than the largest known-viruses and the largest are smaller that the smallest known single-celled eukaryotes
  • Bacterial cells divide by binary fission
• Eukarya

  • Organisms that have eukaryotic cells with nuclei and membrane-bound organelles are placed in this domain
  • They vary massively in size from single-celled organisms several micrometres across to large multicellular organisms many-metres in size, such as blue whales
  • Eukaryotic cells divide by mitosis
  • Eukaryotes can reproduce sexually or asexually
• • Species is the lowest taxonomic rank in the system
  • Similar species can be grouped in a genus
  • Similar genera can be grouped in a family
  • Similar families can be grouped into an order
  • Similar orders can be grouped into a class
  • Similar classes can be grouped into a phylum
  • Similar phyla can be grouped into a kingdom
  • Similar kingdoms can be grouped into a domain
• • Domains are the highest taxonomic rank in the system
• Genome Sequencing

  • Three types of sequence data are used to investigate evolutionary relationships
  • DNA
  • mRNA
  • Amino acids (of a protein)