The Tree of Life Chapter 17

The Linnaean System of Classification Living things must be described 1.5 million identified and named species Identification and naming requires organization Classification systems provide this organization Taxonomy – science of naming and classifying organisms Before the Linean system scientists named newly discovered things however they wanted, often after themselves

The Linnaean System of Classification Each group of organisms is called a taxon (taxa) Basic level is the species Any group of animals that can interbreed In the Linnean System, each species got a name Still in use today

The Linnaean System of Classification Carolus Linnaeus – Father of taxonomy Developed two word naming system – Binomial Nomenclature Always written in italics or underlined Musca domestica or Musca domestica First word is the genus, second is the species

The Linnaean System of Classification Common names vary too much First attempts described physical characteristics What are the flaws of this method? Too long of descriptions Too many varying observations A name might be twenty words long United kingdom refers to buzzards as meaning a hawk, US means a vulture

The Linnaean System of Classification Linnaeus’s system consisted of 7 levels Domain (Largest) Kingdom Phylum Class Order Family Genus Species (Smallest) Each level is called a taxon (taxa) Linnaeus had everything but the domain

The Linnaean System of Classification Levels up always group more organisms together Families are grouped into orders Classes are composed of similar orders Classes make up phylums Linnaeus had two kingdoms – animalia and plantae

The Linnaean System of Classification Linneaus created his system based on physical similarities Flaws? Today scientists genetic information to be sure of similiarities Two unrelated species can evolve similar traits through convergent evolution

Classification Based on Evolutionary Relationships Anything above species has been “invented” How would Linnaeus classify these: Dolphin Hermit crab Sparrow Cow Snake Monkey Bull Shark Scientists have created levels above species to create order

Classification Based on Evolutionary Relationships Phylogeny – evolutionary relationships among organisms Used now instead of physical similarities Evolutionary classification Species in the same genus are more related than species from another genus

Classification Based on Evolutionary Relationships All members of genus share a common ancestor This can be traced through a phylogenic tree The higher the level, the farther back the ancestor The more recent the common ancestor, the more related Members that appear similar may not have a common ancestor even though appearnce would suggest so.

Classification Based on Evolutionary Relationships

Classification Based on Evolutionary Relationships Cladogram – using derived characters to determine evolutionary relationships Clade – group of species that share a common ancestor Derived Characters – characters in recent members, but not older members Result of evolution Demands force new innovations Cladograms are useful in determining how one group branched from another in terms of evolution The more closely related a species, the more derived characters they share

Classification Based on Evolutionary Relationships Cladogram Interpretation Derived characters Nodes – where a branch splits off Identifying clades – snip rule What is the derived character of: Amphibians Crocodiles and birds Snip rule – if you snip off before a node, you are left with a clade

Classification Based on Evolutionary Relationships A lot of classification methods are based on appearance USUALLY, this works…why? DNA/RNA/Proteins are similar in related species These substances are used to make comparisons The more related the DNA is to another organism, the more recently related the organisms are Organisms that appear the same, more than likely will be related because genes determine appearance, however there are animals that can be related that do not look alike

Classification Based on Evolutionary Relationships

Molecular Clocks Evolutionary time can also be measured with DNA Molecular Clock – use DNA mutations to estimate the length of time species have been evolving Scientists have found mutations tend to occur at constant rates for a species Relies on mutations to repeat The more time has passed between two species diverging from a common ancestor, the more mutations there will be Not just one clock running at a time Mutations cause a change in the DNA structure – under the pressure of natural selection More than one molecular clock running at a time

Molecular Clocks Molecular Clocks and Real Time Linking of mutations occurs with geological events and fossil evidence Amino acid differences along with geological splits determines the evolutionary time

Molecular Clocks Different genetic molecules mutate at different rates Some sequences of DNA mutate rapidly, while others are relatively slow Mitochondrial DNA Ribosomal RNA Found only in mitochondria Mutation rate is 10x faster than nuclear DNA Good for closely related species due to speed Always inherited from mother Used to study human lineage for 200,000 years Contained in ribosomes Good for distantly related species Low mutation rate

Domains and Kingdoms Linnaeus started with two kingdoms: Plantae Animalia Scientists realized they needed more This lead to five kingdoms 1866 – Ernest Haeckel realized that single celled organisms needed their own kingdom and made protista 1938 – Herbert Copeland argued prokaryotes were different enough to deserve their own kingdom – Monera 1959 – Robert Whittaker felt that because of the feeding habits of fungi they deserved their own kingdom – Fungi 1977 – Carl Woese found that there were two genetically different types of bacteria leading to the split of monera in to bacteria and archaea Plantae = plants Fungi = fungus Anamalia = animals Protists = are singled celled organisms Monera = bacteria

Domains and Kingdoms Domains – larger and includes the kingdoms Three domains Eukarya Archaea Archaebacteria As more discoveries are made, more kingdoms may be made Because of Woese’s research there are now three accepted domains Eubacteria = archaebacteria

Domains and Kingdoms Domain Bacteria Unicellular Prokaryotic Thick, rigid cell walls around a cell membrane Cell wall made of peptidoglycan

Domains and Kingdoms Domain Archaea Unicellular Prokaryotic Live in extreme environments Volcanic hot springs Brine pools Black mud devoid of oxygen Lack peptidoglycan

Domains and Kingdoms Domain Eukarya All organisms have a nucleus Consists of four kingdoms Protista Fungi Plantae Anamalia

Domains and Kingdoms Kingdom Protista Members have the greatest diversity Cannot be classified as animals, plants, or fungi Most single celled organisms Some are multi-celled algae Some are photosynthetic

Domains and Kingdoms Kingdom Fungi All are heterotrophs Feed on dead or decaying organic matter Most recognizable is the mushroom Most are multicellular, others (Yeast) are unicellular

Domains and Kingdoms Kingdom Plantae Multicellular All are photosynthetic autotrophs Non-mobile

Domains and Kingdoms Kingdom Anamalia Multicellular Heterotrophs Mobile Incredible diversity