18.1 finding order in diversity. to study the diversity of life, biologists use a classification...

18.1 Finding Order in Diversity

Classification

Why Classify?To study the

diversity of life, biologists use a classification system to name organisms and group them in a logical manner.Taxonomy

Assigning Scientific NamesCommon names can be

confusing and vary between regions.

Scientists agreed to use Latin and Greek when assigning scientific names to organisms.

This practice is still followed today as new organisms are discovered.

Binomial NomenclatureTwo-word

naming system used in differentiating a speciesGenus species

A genus is a group of related species.Ursus arctosUrsus

maritimus

Linnaeus's System of ClassificationIncludes seven levels- from smallest to

largestSpecies, Genus, Family, Order, Class, Phylum,

KingdomEach level is called a taxon.

FamilyGenera that share

many characteristics

UrsidaeUrsidae Ursus

arctosUrsidae Ursus

maritimusUrsidae

Ailuropoda melanoleuca

Linnaeus's System of Classification

OrderBroad taxanomic

category composed of similar families

CarnivoraExamples:

CanidaeFelidaeUrsidae

Linnaeus's System of Classification

ClassComposed of

similar orders

MammaliaIncludes

animals that are warm blooded, have body hair, and produce milk for their young.

Linnaeus's System of Classification

PhylumIncludes many

different organisms that share important characteristics

ChordataMammaliaAvesReptiliaAmphibiaSeveral classes of

fish

Linnaeus's System of Classification

Linnaeus's System of Classification

KingdomLargest and most

inclusive level Linnaeus started

with only 2- Animals & Plants

Now, we recognize 6! Plants, Animals,

Protists, Fungi, Archaebacteria, Eubacteria.

18.2 Modern Evolutionary Classification

Classification

Which Similarities Are Most Important?

Organisms determine who belongs in their species by choosing whom they mate with!

Scientists have “invented” larger taxa according to an organisms characteristics.

Evolutionary ClassificationStrategy of

grouping organisms together based on their evolutionary history

Phylogeny- evolutionary relationships among organisms

See Figure 18-7

Evolutionary Classification

Organisms that appear very similar may NOT, in fact, share a common ancestor.

Because… natural selection operating on species in similar ecological environments has often caused convergent evolution.

Classification Using Cladograms

Only identifies and considers characteristics of organisms that are evolutionary innovationsNew characteristics

that arise as lineages evolve over time

Derived Characters- appear in recent parts of a lineage but not in its older members.Can be used to

construct a cladogram

CladogramsDiagram that

shows the evolutionary relationships among a group of organisms

Useful for helping scientists understand how one lineage branched from another in the course of evolution

Like a “Family Tree”

Similarities in DNA & RNAAll organisms have

DNA to pass on to future generations.

The genes of many organisms show important similarities at the molecular level.

Similarities in DNA can be used to help determine classification.

Molecular ClocksComparison of DNA can be used to mark the passage

the time that two species have been separated on the “family tree”

The degree to which genes are dissimilar indicates how far in the past the two species shared a common ancestor.

18.3 Kingdoms & Domains

Classification

The Tree of Life EvolvesAll science adapts to new discoveries.In the early days of classification Linnaeus

proposed a 2-kingdom system.Today, because of new discoveries, we

recognize a six-kingdom system of classification.

Changing Number of Kingdoms

Timeline Names of Kingdoms

1700s Plantae Animalia

Late 1800s

Protista Plantae Animalia

1950s Monera Protista

Fungi Plantae

Animalia

1990s Eubacteria

Archeabacteria

Protista

Fungi Plantae

Animalia

The Three-Domain SystemMolecular clock model analysis has given rise

to a new taxonomic category larger than the kingdoms.Domains

Classification of Living ThingsDOMAIN Bacteria Archaea Eukarya

KINGDOM Eubacteria Archaebacteria

Protista Fungi Plantae Animalia

CELL TYPE Prokaryote Prokaryote Eukaryote Eukaryote Eukaryote Eukaryote

CELL STRUCTURE

S

Cell walls with

peptidoglycan

Cell walls without

peptidoglycan

Cell walls some with cellulose

Cell walls of chitin

Cell walls of

cellulose; chloroplast

s

No cell walls or

chloroplasts

NUMBER OF CELLS

Unicellular Unicellular Most Unicellular

Most Multicellula

r

Multicellular

Multicellular

MODE OF NUTRITION

Autotroph or

Heterotroph

Autotroph or Heterotroph

Autotroph or

Heterotroph

Heterotroph

Autotroph Heterotroph

Domain BacteriaUnicellularProkaryoticThick, rigid cell

walls Have

peptidoglycanCorresponds with

the kingdom EubacteriaEcologically

diverseSome need oxygenSome

photosynthesizeSome are free-

living Some are

parasites

Domain ArchaeaUnicellularProkaryoticCell walls

No peptidoglycan

Unique lipids Extremophiles

Hot springsBrine poolsAnaerobic mud

Domain EukaryaKingdom Protista

Cannot be classified as animals, plants or fungi

Most diverse kingdom

Most unicellularExcept multicellular

algae Autotrophs or

HeterotrophsSome share

characteristics with plants, some with fungi and some with animals.

Domain EukaryaKingdom Fungi

HeterotrophsFeed on

decaying organic matter

Secrete a digestive enzyme and absorb their food

MulticellularMushrooms

UnicellularYeast

Domain EukaryaKingdom Plantae

MulticellularPhotosynthetic

autotrophsNonmotileCell walls with

celluloseIncludes mosses,

ferns, cone-bearing and flowering plants

Domain EukaryaKingdom

AnimaliaMulticellularHeterotrophicNo cell wallsVery diverse

group