Classification

Taxonomy

Science of grouping organisms according to their presumed natural relationships

Artificial

May change with new evidence

History of Classification

Aristotle

Either plant or animal

Animals where they lived

Land Dwellers

Water Dwellers

Air Dwellers

Plants based on stem differences

Herbs

Shrubs

Trees

18th Century

New discovered organisms didn’t fit

Used Latin Descriptions - Cumbersome

Common Names

• Everyday name given to organisms–Don’t describe accurately– Same name for two organisms–May have more than one common name

Carolus Linneaus

Swedish Naturalist – 1707 -1778

Grouped organisms into a hierarchy

Developed system called Binomial Nomenclature

Linneaus’ Hierarchy

KingdomPhylum

ClassOrder

FamilyGenus

Species

Binomial Nomenclature

Means “two names”

Uses Genus and Species

Also called Scientific Name

Rules for Scientific Names

• Describes organism, its range, or honors another scientist

• Name is always Latinized

• Genus – capitalized; Species – Lower Case

• Always italicized or underlined

Levels of Classification with Human Taxonomy

• Kingdom – Animalia• Phylum – Chordata• Class – Mammalia• Order – Primates• Family – Hominidae• Genus – Homo “Man”• Species – Sapiens “Wise One”

The Taxonomist’s Subgroups

Subspecies – morphologically different; geographically separated

Variety – morphologically different; not geographically separated

Strain – biochemically dissimilar group in a species; microorganisms

Domains

• Bacteria – Kingdom Eubacteria

• Archea – Kingdom Archaebacteria

• Eukarya – Kingdoms Protista, Fungi, Plantae, and Animalia

Evidence used in Classification

• Comparative Morphology (Anatomy)• Embryological Evidence• Genetic Similarities• Biochemical Comparisons• Physiological Studies

Comparative Morphology

• Based on physical features• Looks at structural similarities• May or may not be completely accurate• Identification often uses a Dichotomous Key– Set of written choices leading to organism’s name– Branches; selections become more specific

Embryological Evidence

• Usually used for upper categories – Phylum, Class, etc.

• Looks at origin of body organs

• Homologous Organs – common origin, similar function – bat’s wing, human’s arm

• Analogous Organs – Different origin, similar function – insect’s wing vs bird’s wing

Genetic Similarities

• Looks at DNA sequences – related species have more similarities

• Comparison of Karyotypes – picture of organism’s chromosomes

• Chromosome counts• Chromosome shapes

Biochemical Comparisons

• Comparisons of amino acid sequences in common proteins in different species

• More similarities indicate closer relationship

Physiological Studies

Useful in Bacterial Classification

Looks at what chemical bacteria may use as food

May look the same but have different physiologies

Phylogeny

Evolutionary history of a species

Uses evidence of probable evolutionary relationships

Phylogenetic Tree (Cladogram) – model of inferred evolution

Phylogenetic Tree

• Species at branch ends – most recently evolved organisms

• Main Branches and Trunk – organisms which gave rise to more recent organisms

• Close branches imply close evolutionary history

Biosystematics

• Study of reproductive compatibility and gene flow

• Reproductive compatibility used to infer evolutionary relationship

• Studies speciation – evolution of one species into two new species

Kingdom Classifications

Two KingdomsPlants

Animals

Three KingdomsPlants

Animals

Protists

Kingdom Classifications

Four KingdomsPlantsAnimalsProtistsMonera

Five KingdomsPlantsAnimalsProtistsMoneraFungi

Kingdom Classifications

Six KingdomsPlants

AnimalsProtistsFungi

EubacteriaArchaebacteria

Criteria for Defining Kingdoms

• Cell Structure – Prokaryote or Eukaryote

• Number of Cells – Unicellular or Multicellular

• Nutrition – Autotrophs or Heterotrophs

• Reproduction – Asexual or Sexual

Kingdom Characteristics

ArchaebacteriaProkaryoticUnicellular – Cell Walls

without peptidoglycanAutotrophs and

HeterotrophsAsexual/SexualLive in extreme

environments

EubacteriaProkaryoticUnicellular – Cell Walls

with peptidoglycanAutotrophs and

HeterotrophsAsexual/SexualTypical Bacteria

Kingdom Characteristics

ProtistaEukaryoticUnicellular some

MulticellularAutotrophs and

HeterotrophsAsexual/SexualAquatic or Moist Habitats

FungiEukaryoticMulticellular some

UnicellularHeterotrophic by

AbsorptionSexual/AsexualMostly terrestrial, some

aquatic

Kingdom Characteristics

PlantaeEukaryoticMulticellularAutotrophicSexual/AsexualAquatic and terrestrialUsually remain in one

place

AnimaliaEukaryoticMulticellularHeterotrophic by ingestionSexual/Asexual (lower

species)Aquatic and terrestrialMost move about