Classification Introduction

Objectives

• Outline the Linnaean classification system
• Describe a domain
• Describe phylogenetic classification
• Outline the evolution & classification of prokaryotes
• Describe a virus

Taxonomy is the science of classifying organisms.

Carolus Linnaeus

• Swedish botanist in 1700s
• Tried to classify all living things
• Groupings by physical traits
• Known as "father of taxonomy"
• Developed binomial nomenclature

Linnaean System

• Hierarchy of groupings called taxa
• Kingdom most inclusive
• Species most exclusive

Since Linnaeus's time, domain has been added.

Domains

• Bacteria
• Archaea
• Eukaryota (animal, plant, fungus, protist)

After Darwin, scientists looked for ways to classify based on phylogeny, the evolutionary history of a group of related organisms.

One way to do this is to use a clade, a group of organisms that includes an ancestor and all its descendents.

Clades are based on cladistics, a method of comparing traits to determine ancestor-descendent relationships.

Clades are represented by cladograms.

Prokaryotic Domains

Domain Bacteria

• Cyanobacteria contain cholorophyll
• Classified as gram-positive or -negative

Domain Archaea

• Little is known
• Hard to grow in lab
• First discovered in extreme environments
• Now known to live almost everywhere
• Especially abundant in plankton

Prokaryote Metabolism

Metabolism types

• Heterotrophs - use organic compounds
• Autotrophs - use carbon dioxide
• Phototrophic
• Chemotrophic

Virus Characteristics

If a virus were the length of three soccer balls, a prokaryote would be the size of a soccer field.

Viruses

• are not cells.
• lack cell membranes and organelles.
• can't make proteins or reproduce on their own.
• must depend on a host cell.
• ARE NOT LIVING THINGS.

Viruses

• are strands of genetic material within a capsid.
• infect cells, using them to make proteins and reproduce.

A phage is a virus that infects prokaryotes.