Pearland High School 2008

Chapter 18

TheTheDiversityDiversityof Lifeof Life

Tacitus

bellus

Populus tremuloides

Quaking Aspen

Finding Order in Diversity• To study the diversity of life,

biologists use a classification system to name organisms and group them in a logical manner.

• Taxonomy is the branch of biology that groups and names organisms based on studies of their different characteristics.

• Biologists who study taxonomy are called taxonomists.

• Classification systems change with expanding knowledge.

Carolus von Linnaeus(1707-1778)

Carolus Linnaeus• Swedish botanist• Developed Binomial

Nomenclature• Two-word naming system

– Genus» Noun, Capitalized,

Underlined or Italicized

– Species» Descriptive, Lower Case,

Underlined or Italicized

– Each species is assigned a two-part scientific name

» Ex. Ursus arctos

System of Classification

• Linnaeus’s hierarchical system of classification includes seven levels (from largest to smallest)

• Grizzly Bear (common name)– Kingdom Animalia

– Phylum Chordata

– Class Mammalia

– Order Carnivora

– Family Ursidae

– Genus Ursus

– Species arctos

Each of the levels is called a TAXONUrsus

arctos(scientific name)

System of Classification

• Taxonomic categories, an acronym:– Kingdom King– Phylum Phillip– Class Came– Order Over– Family For– Genus Good– Species Soup

KKPPCCOOFFGGSS

• Phylogeny – evolutionary relationships among organisms

• Evolutionary classification – strategy of grouping organisms together based on their evolutionary history– Fossil record– Comparative homologies– Comparative sequencing of

DNA/RNA among organisms– Molecular clocks

Evolutionary Classification

Represent hypothesized evolutionary relationships

Taxonomic Diagrams

PhylogeneticTree

Mammals Turtles Lizards and Snakes Crocodiles Birds

Attempt to trace the process of evolution by

focusing on shared features

Mammals Turtles Lizards and Snakes Crocodiles Birds

CladogramTaxonomic Diagrams

Dichotomous Keys Identify Organisms

• Dichotomous keys contain pairs of contrasting descriptions.

• After each description, the key directs the user to another pair of descriptions or identifies the organism.

Example: 1. a) Is the leaf simple? Go to 2

b) Is the leaf compound? Go to 3

2. a) Are margins of the leaf jagged? Go to 4

b) Are margins of the leaf smooth? Go to 5

Domains• Most inclusive category • Larger than a kingdom• There are 3

– Eukarya – includes the kingdoms»Protists, Fungi, Plants &

Animals– Bacteria – corresponds to the

kingdom Eubacteria– Archaea – corresponds to the

kingdom Archaebacteria

Kingdoms• Monera (Eubacteria and

Archaebacteria) - Prokaryotes, with or without peptidoglycan in cell walls

• Protista – Eukaryotes, diverse, not fungi, plants, or animals

• Fungi – Eukaryotes, multicellular (except yeasts), heterotrophic, chitin in cell walls

• Plantae – Eukaryotes, multicellular, autotrophic, cell wall containing cellulose

• Animalia – Eukaryotes, multicellular, heterotrophic, no cell wall

Kingdom Monera - Eubacteria• Common name: Bacteria• Unicellular prokaryotes• Peptidogylcan in cell wall• Ecologically diverse • Basic shapes are cocci,

bacilli, spirilla• Reproduce both sexually and

asexuallyBacillus anthracis(spores can live in

soil for years)

Streptococcus mutans

(can cause endocarditis and

dental caries)

Kingdom Monera - Archaebacteria• Cell wall does not contain

peptidogylcan• Cell membrane contains unusual

lipids not found in other organisms• Live in extreme environments

(devoid of oxygen):– volcanic hot springs– brine pools– black organic mud

Archaeafirst detected in

extreme environments,

such as volcanic hot springs.

Kingdom Protista• A classification problem – consists

of organisms that cannot be classified as animals, plants, or fungi

• Most unicellular, some colonial and some multicellular

• Autotrophic and heterotrophic• Some move with flagella,

pseudopods or cilia• Animal-like, plant-like and fungus-

like groups• Reproduce by mitosis and meiosis

Entamoeba histolytica

Kingdom Fungi

• Most feed on dead of decaying organic matter by secreting digestive enzymes into their food source then absorbing it into their bodies

• Cell walls of chitin• Most multicellular; some

unicellular• Heterotrophic

Boletus zelleri(Edible, but often infected with fly

larvae)

Epidermophyton floccosum

(one of the causes of

athlete's foot)

Kingdom Plantae

• Multicellular• Nonmotile – cannot

move from place to place

• Cell wall with cellulose• Mostly photosynthetic

autotrophs

Sunflowers in Fargo, North

Dakota

Ginkgo bilobaGinkgos are often very long-lived.

Some specimens are thought to be more than 3,500

years old.

Kingdom Animalia

• Multicellular• Heterotrophic• No cell walls or

chloroplasts• Incredible diversity

Chambered

Nautilus

Colony of sponges

Hymenoptera Dialictus zephrum

Txodes scapularisDeer tick

Hierarchical Systemof Classification

Domain

Kingdom

Phylum

Class

Order

Family

Genus

SpeciesFrom

general to more specific

How Many Kingdoms?

6Kingdoms