SPECIES AND TAXONOMY

• SPECIES: a group of organisms that share similar characteristics that can interbreed to produce fertile offspring
• PHYLOGENETICS / PHYLOGENY: is based on evolutionary relationship between organisms tells us who’s related to whom and how closely related they are
• CLASSIFICATION: the grouping of organisms
• PHYLOGENETIC CLASSIFICATION: a phylogenetic classification system arranges species into groups based on their evolutionary origins and relationships
• HIERARCHY: an arrangement of taxa where the smaller groups are placed within larger groups with no overlap between groups
• TAXONOMY: the practice and science of classification of the groups (taxa)
• SPECIES: A group of organisms that share similar characteristics that can interbreed to produce fertile offspring.

  • they are therefore able to produce more offspring. This means that when a species reproduces sexually any of the genes of its individuals can be combined with any other
  • a species is the basic unit of classification
• BINOMIAL NOMENCLATURE - FEATURES

  • its a universal system based upon Latin or Greek names
  • organisms are identified by two names
  • the first name is the generic name which denotes the genus to which the organism belongs. Like the surname used to identify people and shared by their close relatives.
  • the second name is the specific name which denotes the species to which the organism belongs. This is equivalent to the first (or given) name used to identify people. However, unlike in humans, it’s never shared by other species within the genus.
• BINOMIAL NOMENCLATURE - RULES

  • the names are printed in italics or if handwritten they’re underlined to indicate that they’re scientific names eg. Homo sapiens
  • the first letter of the generic name is in upper case (capitals), but the specific name is in lower case (small letters)
  • if the specific name isn’t known, it can be written as ‘sp.’ For example, Felix sp.
• WHAT IS COURTSHIP BEHAVIOUR?

  Courtship behaviour is carried out by organisms to attract a mate of the right species. It can be fairly simple or quite complex. Courtship behaviours can be performed by either the male or the female or may sometimes involve both sexes. During courtship, animals use signals to communicate with a potential mate and with members of their own sex
• WHY IS COURTSHIP BEHAVIOUR IMPORTANT?

  SURVIVAL OF THE SPECIE THROUGH REPRODUCTION, ENABLES INDIVIDUALS TO:

  1. RECOGNITION OF MEMBERS OF OWN SPECIES - to ensure mating only takes place between members of the same species to produce fertile offspring
  2. IDENTIFYING A MATE THATS CAPABLE OF BREEDING - sexually mature, fertile, receptive
  3. FORM A PAIR BOND - leads to successful mating and raising of offspring
  4. SYNCHRONISE MATING - so it takes place when there’s maximum probability of fertilisation
  5. BECOMING ABLE TO BREED - physiological state
• STIMULUS RESPONSE CHAIN: is a chain of actions that is the same for all members of the same species, but different for different species.
• STIMULUS RESPONSE CHAIN: 1

  A stimulus response chain: a chain of actions that is the same for all members of the same species, but different for different species.

  • This enables individual to tell if prospective partner is of same species
  • also tells whether the partner is ready to mate
  • #Females of many species undergo cycle of sexual activity where they can only conceive during a very short time only receptive to mating for a period around the time when they produce eggs
  • #Courtship behaviour - used by males to determine whether female is at this receptive stage.
• STIMULUS RESPONSE CHAIN: 2

  • #lf she responds with the appropriate behavioural response, courtship continues and is likely to result in the production of offspring.
  • #If she is not receptive, she exhibits a different pattern of behaviour and the male turns his attentions elsewhere.
  • The longer the chain, the more likely mating.
• ROLE OF COURTSHIP BEHAVIOUR IN SPECIES RECOGNITION

  • courtship behaviour is specific for each species
  • this allows members of the same species to recognise each other, preventing interbreeding and making reproduction more successful (as mating with the wrong species won’t produce fertile offspring)
  • because of this specificity, courtship behaviour can be used to classify organisms
  • the more closely related species are, the more similar their courtship behaviour
• PHYLOGENY: based on evolutionary relationship between organisms it tells us who’s related to whom and how closely related they are

  • the term is derived from the word phylum which in classification is a group of related or similar organisms
  • all organisms have evolved from shared common ancestors (relatives)
  • the phylogeny of an organism reflects the evolutionary branch that led up to it
  • the phylogenetic relationships of different species are usually represented by a tree-like diagram called a phylogenetic tree
• PHYLOGENETIC TREES

  • the first branch point represents a common ancestor of all the family members
  • each of the following branch points represent another common ancestor from which a different group diverged
  • the oldest species is at the base of the tree while the most recent ones are represented by the ends of the branches
  • closely related species diverged away from each other most recently

  -eg. Humans and chimpanzees are closely related, as they diverged very recently. You can see this because their branches are close together.

  
• PHYLOGENETIC CLASSIFICATION (HIERARCHAL)

  • PHYLOGENETIC CLASSIFICATION SYSTEM: arranges species into groups based on their evolutionary origins and relationships
  • HIERARCHY: an arrangement of taxa where the smaller groups are placed within larger groups with no overlapping between groups
• PHYLOGENETIC CLASSIFICATION (HIERARCHAL)

  • grouping of organisms (classification) using shared features derived from their ancestors (phylogenetic)
  • arranges the group into a hierarchy
  • each group is a taxon
  • relationships in a phylogenetic classification are partly based on homologous characteristics

  -homologous characteristics have similar evolutionary origins regardless of their functions in the adult of a species

  -eg. The wing of a bird, the arm of a human + front leg of a horse all have the same basic structure + evolutionary origins + are therefore homologous
• TAXONOMY: practice and science of classification of the groups (taxa)


  • taxa are positioned in a hierarchy order - known as taxonomic ranks
  • with largest groups at top, smallest at bottom - makes it easier to identify + study them
  • scientists now consider phylogeny when classifying organisms + group organisms according to their evolutionary relationships
  • as you move down hierarchy, there are more groups at each level but fewer organisms in each group
  • organisms in each group become more closely related
  • hierarchy ends with species
• WHY DO SCIENTISTS CONSTANTLY UPDATE CLASSIFICATION SYSTEMS? taxonomy

  Because of discoveries about new species and new evidence about known organisms (eg. DNA sequence data)
• HIERARCHY OF TAXONOMIC RANKS

  TAXON:

  • domain - dirty
  • kingdom - king
  • phylus - Philip
  • class - comes
  • order - over
  • Family - for
  • genus - garlic — Genera plural
  • species - sausages
• 3 DOMAINS

  • eukarya
  • bacteria
  • archaea
• CARRYING EVOLUTIONARY RELATIONSHIPS

  Evolutionary relationships used to be clarified by observable characteristics. Now advances in immunology and genome sequencing help to clarify evolutionary relationships between organisms.
• GENOME SEQUENCING

  Compare the order of base sequence of whole genome of different species

  • advances in genome sequencing have meant that the entire base sequence of an organisms DNA can be determined
  • the DNA base sequence of one organism can then be compared to the DNA base sequence of another organism, to see how closely related they are
  • Closely related species will have a higher percentage of similarity in their DNA base sequence when putting one above the other

  HIGHER % MATCH = MORE CLOSELY RELATED
• IMMUNOLOGICAL COMPARISONS

  • similar proteins will bind same antibodies
  • if antibodies to a human version of a protein are added to samples from other species, any proteins (antigens) that are similar (enough) to the human version will also bind to the human antibodies
  • proteins that bind antibodies will form a precipitate (a solid mass in a solution)
  • the more precipitate (proteins) there is = the more similar the proteins are so the more related they are