Chapter 18 Classification

Classifying• A great diversity of organisms requires a universal

way to name them• Taxonomy – allows biologists to name and classify

organisms in a logical manner- usually based on similarities and

differences in appearanceEx: teachers and mechanicsvs. biology teachers and auto mechanics

Scientific Naming• Carolus Linnaeus – Swedish botanist brought order and

devised a system for naming and categorizing organismsBinomial Nomenclature – two word system of

scientific nameGenus (capitalized and italized) – depicts species

association- Specific epithet (lower case italized) – unique species within genusEx: Ursus arctos Canis familiaris

Hierarchical Classification• System of levels that categorize organisms in

increasingly more specific groups- Broad at the top to most specific at the bottom- Organisms grouped at the bottom share more common characteristics compared to organisms near the top

Hierarchical ClassificationDomain - 3 domains (Eukarya, Bacteria, Archaea)

Kingdom – 4 kingdoms within EukaryaPhylumClassOrderFamilyGenusSpecies

Hierarchical Classification

Classification

Evolutionary Classification• Phylogeny- grouping organisms into categories

that represent lines of evolutionary descent- Refers to the evolutionary history of a species or group of species- Usually constructed from fossil record to describe origin.

Cladograms• Cladistic analysis - identifies characteristics that are new

and innovative as lineages of a species evolved over time• Derived characters – features that appear in recent parts

of lineage but not in older members• Cladogram – diagram that shows evolutionary

relationship among groups of organisms- depicts patterns of shared characteristics- useful in understanding how one lineage branched

from another- resembles a family tree

Cladograms

Cladograms

DNA & RNA• Organisms of different anatomies can have

common traits – How?• All organisms use DNA and RNA to pass on

information and to control cell growth and development.

• Genes can show similarities at the molecular level and can help determine classification and evolutionary relationships

Molecular Clocks• Molecular clocks - use DNA comparisons to

estimate the length of time that 2 species have been evolving independently- relies on mutations to indicate time- DNA sequences of 2 species can show dissimilarity- any degree on difference indicates how long ago the 2 species may have shared a common ancestor

Domains• Bacteria

- unicellular and prokaryotic- thick, rigid cell wallsKingdom – Eubacteria- diverse organisms that are both free living and deadly parasites- some are photosynthetic- some require oxygen, other are anaerobicEx: E. coli, Streptococcus

Domains• Archaea

- unicellular and prokaryotic- extremophiles- live in extreme habitats

1. thermophiles - volcanic hot springs ( hydorthermal vents)

2. Halophiles - Brine pools (Dead sea)

3. Methanogens – black organic mud (sewage treatment)

Domains• Eukarya

Eukaryotic – unicellular and multicellular4 Kingdoms

1. Protista – paramecium, green algae 2. Fungi – yeast, mushrooms3. Plantae – cell walls, chloroplasts4. Animalia- you