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
•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