Classification of Living Things Taxonomy, Hierarchical Classification, Binomial Nomenclature, Genetic Variation, Relatedness, Phylogeny
Kingdoms • Classification – we all do it • Main classification by Aristotle • Plantae and Animalia • Does not always fit – sponges and corals fixed in one place however they do not make their own food through photosynthesis • Microscopes further clouded the process • Haeckel (1866) – created a third kingdom • Protista • "first established beings“ • "better regarded as a loose grouping of 30 or 40 disparate phyla with diverse combinations of trophic modes, mechanisms of motility, cell coverings and life cycles.”
Kingdoms • Fungi – were originally included with Plants • They do not carry out photosynthesis though and absorb food into their bodies • Bacteria – lack a nucleus and other organelles and can gain energy in a variety of environments • They were given their own kingdom as well • Sometimes known as Eubacteria, Prokaryotae or Monera • Archaea – kingdom created in the 1990’s • For bacteria that live in very unique environments • Acidic springs, salt lakes, hot springs
Prokaryotes & Eukaryotes • Two main types of cell types based on differences in size, structure and other characteristics • Fossil evidence • Prokaryotic cells – 3.5 billion years ago • Eukaryotic cells – 1.5 billion years ago • Multicellular organisms – 700 million years ago
Kingdoms - subdivided • Domains • Bacteria • Archaea • Eukarya • Within Eukarya we find the protists and it is believed that they should be further divided • Agreement is difficult
Taxonomy • Classifying organisms • Taxis – arrangement; Nomos – law • Carolus Linnaeus – circa 1750 • Used physical characteristics to classify organisms into groups • Latin and Greek stems (Felis domesticus) • Names given often reflect characteristics of organism or to honour a scientist or historical figure
Hierarchy of Groups • Horse is more like a dog then a shark • Horses and dogs are mammals • Horse is more like a shark then an oyster • Vertebrates vs. invertebrates • Each kingdom is broken down into smaller groups called taxon (plural taxa) to assist with categorization • Kingdom is largest down to species
Hierarchy of Groups Plantae--includes all plants Magnoliophyta--flowering plants Magnoliopsida--dicots Magnoliidae--subclass for Magnolia-like plants Magnoliales--order for Magnolia-like plants Magnoliaceae--family for Magnolia-like plants Magnolia--genus includes all Magnolias grandiflora--specific epithet • The name for a species consists of the genus name and the specific epithet. **Notice that the endings will always tell you what rank you are dealing with, even if you don't recognize the word. For example, the word "Sterculiaceae" could only refer to a family. • As you go up, each category is made of groups of members of the category below it--e.g., there are many types of Magnolia but they all fit into the genus Magnolia. The Magnolias and their relatives are all in the Magnoliaceae. Orders are made up of families, subclasses are made of orders, etc.
Binomial Nomenclature • Using two words for each species • Genus and species names used • Canis lupus (wolf); Canis latrans (coyote); Canis familiaris (domestic dog) • Common Names • Problematic because they are not standard • Mountain lion, puma and cougar • P. 395, fig. 11.13
Origins of Diversity • Similar to others in your species but not exactly the same • Diversity between species begins within a species • Certain different characteristics found between two populations in response to their environment may allow new species to develop • First described in 1859 by Charles Darwin in his book: On the Origin of Species by Means of Natural Selection
Genetic Variation • Changes in characteristics are produced by: • Random genetic mutations • Introduce variety • Especially important in asexual organisms • Selection for a particular characteristic that increases the organisms chance of survival and breeding in a particular environment
Determining Relatedness • Taxonomy involves evolution • A need to determine the evolutionary history of groups of organisms • Comparing different species living today with those that lived in the past • Ways by which scientists determine relatedness • Anatomy, development, biochemistry, DNA
Evidence from Anatomy • Classification between major classes can be difficult • Archaeopteryx – 150 million years ago • Fossils not required to find anatomical evidence of evolution • Human arm, horse’s leg, bat’s wing and whale’s flipper • All specialized for what they do but they have the same evolutionary origin - homologous
Further Evidence • Development • Relatedness due to appearance can be a dangerous mistake • Larval and adult forms of organisms can be very different and they are the same species!
Further Evidence • Biochemistry • Comparisons due the molecules from which organisms are made • Comparisons of proteins and hormones • Horseshoe crab is more similar to spiders then to other crabs
Further Evidence • DNA • Genes consist of sequences of nucleotide bases in a segment of DNA • Human single strands of DNA are compared to other organisms and the amount of complementary base pairing that occurs indicates relatedness • 93% match with the macaque monkey • 98% match with the chimpanzee • DNA can also help to determine how long ago species began to diverge from a common ancestor • Mitochondrial DNA – mother to offspring • It mutates at a predictable rate so it provides a molecular clock for measuring rates of evolution
Phylogeny • “True” evolutionary history of groups of organisms • Common ancestors share characteristics of all organisms that come after in a phylogenetic tree • Smaller differences help to distinguish genus’ from each other
Phylogeny • Order Artiocactyla • Even number of hoofed toes on hindfoot; specialized teeth and digestive systems for vegetation • Family Bovidae – horns • Family Cervidae – antlers • Genus Cervus – highly branched antlers • Genus Rangifer – broad, palmate antlers (hand shaped)
Cladistics • Classification scheme based on phylogeny • Based on idea that each group of related species has one common ancestor • The current organisms retain some ancestral characteristics and gain some unique characteristics as they diverge from the ancestor • Cladogram – like a phylogenetic tree but is used to test alternative hypothesis about differences in branching history
Phylogeny vs. Cladistics • A phylogenetic tree is a specific type of cladogram where the branch lengths are proportional to the predicted or hypothetical evolutionary time between organisms or sequences • The term "cladogram" emphasizes that the diagram represents a hypothesis about the actual evolutionary history of a group, while "phylogenies" represent true evolutionary history. • To other biologists, "cladogram" suggests that the lengths of the branches in the diagram are arbitrary, while in a "phylogeny," the branch lengths indicate the amount of character change.
Phylogeny vs. Cladistics • Bioinformaticians produce cladograms representing relationships between sequences, either DNA sequences or amino acid sequences. However, cladograms can rely on many types of data to show the relatedness of species. • In addition to sequence homology information, comparative embryology, fossil records and comparative anatomy are all examples of the types of data used to classify species into phylogenic taxa. • So, it is important to understand that the cladograms generated by bioinformatics tools are primarily based on sequence data alone.
Value of Phylogeny • Relatedness can have important consequences • Sources of drugs, hormones and other medical products the search can be narrowed to closely related organisms with similar proteins or chemicals • Transmission of disease • Increase in crop yields due to cross breeding to increase biological control • Where are we going?