ch 18- classification why do biologists organize living organisms into groups that have biological...

Ch 18- Classification

• Why do biologists organize living organisms into groups that have biological meaning?– Study the diversity of life

• Use classification system to name organisms and group them in logical manner

• Taxonomy- discipline of classifying organisms and assigning each organism a universally accepted name

Scientific Names

• Why don’t scientists use common names?• Use Latin and Greek • Bionomial nomenclature- two word naming system

– Each species given two-part scientific name– Carolus Linnaeus– First word is capitalized, second word is lowercased, written in

italics– Ursus arctos- grizzly bear

• Ursus- genus to which organism belongs– Genus- group of closely related species

• artos- unique to each species within the genus

Linnaeus’s System of Classification• Linnaeus’s hierarchical system of classification uses seven taxonomic categories

– Species– Genus– Family– Order– Class– Phylum– Kingdom

• Taxon- taxonomic category• Family- genera that share many characteristics

– Ursidae• Order- broad taxonomic category composed of similar families

– Carnivora• Class- composed of similar orders

– Mammalia• Phylum- several classes that share important characteristics

– Chordata• Kingdom- largest and most inclusive categories

– Animalia

Sec 2- Modern Evolutionary Classification

• Phylogeny- evolutionary relationships among organisms

• How are evolutionary relationships important in classification?– Organisms are grouped into categories that

represent lines of evolutionary descent, or phylogeny- not just physical similarities

• Evolutionary classification- grouping organisms together based on their evolutionary history

Classification Using Cladograms

• Cladistic analysis identifies new characteristics that arise as lineages evolve over time

• Derived characters- characteristics that appear in recent parts of a lineage but not in its older members– Evolutionary innovation, or new characteristics

• Cladogram- diagram that shows evolutionary relationships among group of organisms– Help understand how one lineage branched from another– Use derived characters

Similarities in DNA and RNA

• All organisms use DNA and RNA to pass on information• How can DNA and RNA help scientists determine evolutionary

relationships?– Genes of many organisms show important similarities at molecular

level– Can be used to determine classification and evolutionary relationships

• Similar genes– Human muscles and yeast

• DNA evidence– More similar DNA sequence of two species, the more recently they

shared a common ancestor– American vulture, African vulture, stork

Molecular Clocks

• Uses DNA comparisons to estimate the length of time that two species have been evolving independently

• Relies on mutations• Comparison between DNA sequences can

reveal how dissimilar the genes are- indicates how long ago two species shared a common ancestor

Sec 3- Kingdoms and Domains

• How many kingdoms of life are there?• What are the 6 kingdoms?

– Eubacteria– Archaebacteria– Protista– Fungi– Plantae– Animalia

• Domain- taxonomic category larger than kingdom– Eukarya- composed of protists, fungi, plants, animals– Bacteria- Eubacteria– Archaea- Archaebacteria

Domain Bacteria and Archaea

• Bacteria- unicellular and prokaryotic– Thick, rigid cell walls– Ecologically diverse- free living to deadly parasites– Some photosynthetic, some not– Some depend on oxygen, some not

• Archaea- unicellular and prokaryotic– Most extreme environments– Many survive only in absence of oxygen– Cell walls lack peptidoglycan– Unusual lipids in cell membranes, not found in any other

organism

Domain Eukarya• All have nucleus• Protista, Fungi, Plantae, Animalia• Protista- display greatest variety

– Unicellular and multicellular– Photosynthetic and heterotrophic

• Fungi- heterotrophs– Feed on dead or decaying organic matter– Unicellular or multicellular

• Plantae- multicellular organisms that are photosynthetic autotrophs

• Animalia- multicellular and heterotrophic – Incredible diversity