Classification and Taxonomy

• Species are defined as a collection of organisms with similar features and genetics which reproduce to make offspring which are fertile.
• What is the definition of species?

  A collection of organisms with similar features and genetics which reproduce to make offspring which are fertile.
• Why is the definition of species debated?

  It is impractical to see if two animals can breed to make fertile offspring, or in the case of bacteria, they reproduce asexually
• Courtship behaviour is an important factor to consider when classifying species
• Courtship behaviour is a series of behaviours that males and females use to attract each other
• Organisms with the same species can mate to produce fertile offspring.
• It is important that organisms only breed with individuals of the same species so that they can pass their genes to their offspring.
• Potential mates of the same species can be identified through courtship behaviours, which are complex displays that help an individual attract a male.
• How can potential mates be identified?

  Courtship rituals
• Courtship behaviours are useful when classifying species because they are species-specific
• Individuals of the same species will do the same courtship behaviour, and only individuals within the same species will respond to the courtship behaviour, and so they are a useful tool for classifying species.
• What are some examples of courtship behaviour?

  • Releasing a chemical
  • Using sound
  • Colour/visual displays
  • Dancing
  • Building nests and shelters
• Releasing a chemical is used by many insects to release pheromones to attract mates to their territory
• Birds use sound and calls that is specific to each species that are used to attract males.
• Many birds and some reptiles have brightly coloured patches which are displayed to mates to represent physical fitness, it takes a lot of energy to produce pigments.
• Birds can perform elaborate dance routines which are judged by mates before mating can occur
• Collections of materials to build shelters demonstrates to a mate that they can provide and protect them and their offspring
• Phylogeny is the grouping of organisms based on their evolutionary relationships between organisms, and can help to classify organisms.
• What is phylogeny?


  The grouping of organisms based on their evolutionary relationships using common ancestry
• Phylogenies are used to understand the evolutionary relationships between organisms, and can help to classify organisms.
• What can phylogenies be used for?

  To understand the evolutionary relationships between organisms and to help classify organisms
• The evolutionary relationship of an organism or group of organisms is called its phylogeny.
• Phylogenies are based on the fact that all organisms will share a more recent common ancestor than more distantly related organisms.
• More commonly related organisms will share a more recent common ancestor than more distantly related organisms
• A phylogenetic tree shows the evolutionary relationship between different species and their most recent common ancestor
• What does a phylogenetic tree show?


  The evolutionary relationships between organisms
• Each branch on a phylogenetic tree shows a different species, and the point that two branches join together is the most common ancestor of the two species.
• What does each branch on a phylogenetic tree show?

  A different species
• What does the point where two branches join on a phylogenetic tree show?

  The most common ancestor of the two species
• Genes important in the embryonic development of animals have been relatively well conserved during evolution, this means they are more similar among different species than many other genes.
• Genetic conservation can be explained across species as changes in the genes that are important to embryonic development have been relatively minor as mutational changes in the embryo has magnified consequences in the adult
• Why have genes been conserved across species?

  Changes in the genes that are important to embryonic development have been relatively minor as mutational changes in the embryo has magnified consequences in the adult
• Darwin first thought of phylogeny as a way of classifying organisms, he was limited however as he did not know about genetic yet
• Why was Darwins original theory of phylogeny limited?

  He didn’t yet know about genetics
• Up until Darwin, organisms were classified using the Linnaean method, which just grouped organisms based on their structure and characteristics.
• How did the Linnaean method group organisms?

  Based on their structure and characteristics
• What are the advantages of phylogenetic classification over hierarchial?

  Connects groups based on their evolutionary relationships rather than their characteristics, allows a continuum rather than discrete group and gives a better description of the variety present in groups, showing the changes over time
• Phylogenetic classification connects groups based on their evolutionary relationships rather than their characteristics, like in the hierarchical method of classification.
• Phylogeny allows a continuum rather than the discrete groups present in the hierarchical classification method
• Phylogeny gives a better description than the hierarchical method of the variety present within groups, rather than giving the impression that all groups are equal in age, it shows changes over time.