18-1 Finding Order in Diversity

Section 18-1Finding Order in Diversity

To study the diversity of life, biologists use a classification system to name organisms and group then in a logical manner.

Taxonomists are scientists that classify organisms into groups that have biological significance and assign each organism a universally accepted name.

Binomial NomenclatureDeveloped by a Swedish botanist, Carolus Linnaeus, in the 18th century.Each species is assigned a two-part scientific name that is always written in italics. The first word is capitalized, and the second word is lowercased.The first word is the genus and the second word is unique to each species of the genus. It is usually a Latinized description of some important trait of the organism or an indication of where the organism lives.Examples, Ursus maritimus – polar bear; Ursus arctos, grizzly bear

Why use a dead language?

•We only know about a fraction of the organisms that exist or have existed on Earth.

•Taxonomists give a unique scientific name to each species they know about whether it’s alive today or extinct.

• The scientific name comes from one of two “dead” languages – Latin or ancient Greek.

Devil Cat

Ghost Cat

Mountain Lion

Screaming Cat

Puma

Florida Panther

Cougar

•There are at least 50 common names for the animal shown on the previous 7 slides.

•Common names vary according to region.

•Soooo……why use a scientific name?

Section 18-1

Flowchart

Linnaeus’s System of Classification

Kingdom

Phylum

Class

Order

Family

Genus

Species

Linnaeus’s classification system is hierarchical; it consists of levels. Each level is called a taxon.

Grizzly bear Black bear Giant panda

Red fox Abert squirrel

Coral snake

Sea star

KINGDOM Animalia

PHYLUM Chordata

CLASS Mammalia

ORDER Carnivora

FAMILY Ursidae

GENUS Ursus

SPECIES Ursus arctos

Section 18-1

Figure 18-5 Classification of Ursus arctos

HumansDomain Eukarya

Kingdom Animalia

Phylum Chordata

Sub Phylum Vertebrata

Class Mammalia

Order Primates

Family Hominidae

Genus Homo

Species sapien

Scientific name: Homo sapien

Section 18-2

Evolutionary Classification

Species within a genus are more closely related to each other than to species in another genus because all members of a genus share a recent common ancestor.

All genera in a family share a common ancestor that is further in the past than the ancestor of the entire order.

The higher the level of the taxon, the further back in time is the common ancestor of all the organisms of the taxon.

A phylogenetic tree is a family tree that shows a hypothesis about the evolutionary relationships thought to exist among groups of organisms. It does not show the actual evolutionary history of organisms.

Why a hypothesis?

Phylogenetic trees are usually based on a combination of these lines of evidence:

    Fossil record

    Morphology

    Embryological patterns of development

    Chromosomes and DNA

Section 18-2

Evolutionary Classification

Cladistic analysis identifies and considers only those characteristics of organisms that are evolutionary innovations.

Derived characteristics are those that appear in recent parts of a lineage but not in its older members.

Used to construct a cladogram, a diagram that shows the evolutionary relationships among a group of organisms.

There are three basic assumptions in cladistics:

1.Organisms within a group are descended from a common ancestor.

2.There is a bifurcating pattern of cladogenesis.

3.Change in characteristics occurs in lineages over time.

CLADOGRAM

Appendages Conical Shells

Crab Barnacle Limpet Crab Barnacle Limpet

Crustaceans Gastropod

Molted exoskeleton

Segmentation

Tiny free-swimming larva

Section 18-2

Traditional Classification Versus Cladogram

Classifying species based oneasily observed adult traits canpose problems. Which of these three organisms seem most alike?What additional information might you gather to help inform yourdecision?

CLASSIFICATION BASED ON VISIBLE

SIMILARITIES

CLASSIFICATION BASED ON VISIBLE

SIMILARITIES

CLADOGRAM

Appendages Conical Shells

Crab Barnacle Limpet Crab Barnacle Limpet

Crustaceans Gastropod

Molted exoskeleton

Segmentation

Tiny free-swimming larva

Section 18-2

Traditional Classification Versus Cladogram

Biologists now group organisms into categories that represent lines of evolutionary descent, or phylogeny, not just physical similarities. This strategy is called evolutionary classification.

• A key is a device for easily and quickly identifying an unknown organism.

• The dichotomous key is the most widely used type in biological sciences.

• The user is presented with a sequence of choices between two statements, couplets, based on characteristics of the organism. By always making the correct choice, the name of the organism will be revealed.

The Dichotomous Key

                                                            

Section 18-2

Evolutionary Classification

In addition to physical characteristics, similarities in DNA and RNA can be used to help determine classification and evolutionary relationships.

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

The more similar the DNA sequence of two species, the more recently they shared a common ancestor, and the more closely they are related in evolutionary terms.

Section 18-3

Kingdoms and Domains

The six-kingdom system of classification includes the kingdoms Eubacteria, Archaebacteria, Protista, Fungi, Plantae, and Animalia

The three domains are Eukarya, Bacteria, and Archaea. The domain Eukarya includes the kingdoms Protista,

Fungi, Plaintae, and Animalia. The domain Bacteria includes the kingdom Eubacteria. The domain Archaea includes the kingdom

Archaebacteria.

Section 18-3

Concept Map

are characterized by

such as

and differing which place them in

which coincides withwhich coincides with

which place them in which is subdivided into

Living Things

Kingdom Eubacteria

Kingdom Archaebacteria

Eukaryotic cellsProkaryotic cells

Important characteristics

Cell wall structures

Domain Eukarya

Domain Bacteria

Domain Archaea

Kingdom Plantae

Kingdom Protista

Kingdom Fungi

Kingdom Animalia

Section 18-3

Domain Bacteria

Characteristics of Domain Bacteria Kingdom Eubacteria Unicellular and prokaryotic Thick, rigid cell walls surrounding a cell membrane Cell walls contain peptidoglycan Ecologically diverse, ranging from free-living soil organisms to

deadly parasites Some are photosynthetic Some anaerobic

Section 18-3

Domain Archaea

Characteristics of Domain Archaea Kingdom Archaebacteria Unicellular and prokaryotic Thick, rigid cell walls surrounding a cell membrane Cell walls lack peptidoglycan Cell membranes contain unusual lipids found only in Archaea Live in some of the most extreme environments (hot springs, brine

pools, and black organic mud) Many are anaerobic

Section 18-3

Domain Bacteria

Characteristics of Domain Eukarya Eukaryotes (organisms with a nucleus)

Kingdom Protista

- cannot be classified as animals, plants, or fungi

- greatest variety

- most unicellular; some colonial; some multicellular

- cell walls of cellulose in some; some have chloroplasts

- some photosynthetic, others are heterotrophic

- some share characteristics with plants, others with fungi, and others with animals

- animal-like protist include Euglena, Paramecium and Amoeba

- other examples include algae, slime molds, and giant kelp

Section 18-3

Domain Eukarya

Characteristics of Domain Eukarya, continuedKingdom Fungi

- cell walls of chitin

- most multicellular (mushrooms); some unicellular (yeasts)

- heterotrophic

- often found on dead or decaying organic matter; secrete digestive enzymes into their food source; absorb smaller molecules into their bodies

Section 18-3

Domain Eukarya

Characteristics of Domain Eukarya, continuedKingdom Plantae

- multicellular, photosynthetic autotrophs

- nonmotile – cannot move from place to place

- cell walls that contain cellulose; have chloroplasts

- includes cone-bearing plants, flowering plants, mosses, and ferns

Kingdom Animalia

- multicellular, heterotrophs

- no cell walls

- mobile for at least some part of their life cycle

- incredible diversity

- examples include sponges, worms, insects, fishes, and mammals

DOMAIN

KINGDOM

CELL TYPE

CELL STRUCTURES

NUMBER OF CELLS

MODE OF NUTRITION

EXAMPLES

Bacteria

Eubacteria

Prokaryote

Cell walls with peptidoglycan

Unicellular

Autotroph or heterotroph

Streptococcus, Escherichia coli

Archaea

Archaebacteria

Prokaryote

Cell walls without peptidoglycan

Unicellular

Autotroph or heterotroph

Methanogens, halophiles

Protista

Eukaryote

Cell walls of cellulose in some; some have chloroplasts

Most unicellular; some colonial; some multicellular

Autotroph or heterotroph

Amoeba, Paramecium, slime molds, giant kelp

Fungi

Eukaryote

Cell walls of chitin

Most multicellular; some unicellular

Heterotroph

Mushrooms, yeasts

Plantae

Eukaryote

Cell walls of cellulose; chloroplasts

Multicellular

Autotroph

Mosses, ferns, flowering plants

Animalia

Eukaryote

No cell walls or chloroplasts

Multicellular

Heterotroph

Sponges, worms, insects, fishes, mammals

Eukarya

Classification of Living Things

Section 18-3

Figure 18-12 Key Characteristics of Kingdoms and Domains

KingdomsEubacteria

Archaebacteria

Protista

Plantae

Fungi

Animalia

DOMAIN EUKARYA

DOMAIN ARCHAEA

DOMAIN BACTERIA

Section 18-3

Figure 18-13 Cladogram of Six Kingdoms and Three Domains

Modern Hominoids