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Why Classify? Biologists have identified and named about 1.5 million species and estimate that anywhere between 2 and 100 million additional species have yet to be discovered.

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chapter 18 classification

Why Classify?

Biologists have identified and

named about 1.5 million species

and estimate that anywhere

between 2 and 100 million

additional species have yet to

be discovered.

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

Chapter 18: Classification

slide2

Referring to organisms by their common names can be quite confusing. (ex: buzzard in UK = hawk, buzzard in U.S. = vulture)

  • Catfish, starfish, seahorse, jellyfish…. What are they?
  • A Swedish botanist named Carolus Linnaeus developed a two-word naming system called binomial nomenclature.
section 18 1 finding order in diversity
Section 18.1 – Finding Order in Diversity
  • Good classification does two things:
    • Organized into groups that have biological similarities
    • Organize according to unique/important characteristics/how related
slide5

Binomial Nomenclature (naming system)

  • 2 part scientific name
  • Genus species
    • Italicize letters
    • Genus Capitalized; species lowercase
  • EX. Panthera pardus panther or leopard

(genus species) same species, different common name)

slide6

FYI: The genus Ursus contains 5 other kinds of bears, including polar bears, black bears, and brown bears.

  • The polar bear, for example has the scientific name Ursus maritimus.
  • The second part of a scientific name – maritimus, is unique to each species within the genus.
  • Often, this part of the name is a Latinized description of

some important trait or an indication of where it lives.

  • For example, the Latin word maritimus

refers to the sea, where polar bears live.

  • Another example – humans: Homo sapiens
frogs toads of illinois fyi
Frogs & Toads of Illinois FYI
  • American toad (Bufo americanus)
  • Blanchard’s cricket frog (Acris crepitans blanchardi)
  • Bullfrog (Rana catesbeiana)
  • Cope’s gray treefrog (Hyla chrysoscelis)
  • Crawfish frog (Rana areolata)
  • Eastern gray treefrog (Hyla versicolor)
  • Eastern spadefoot (Scaphiopus holbrooki)
  • Fowler’s toad (Bufo fowleri)
  • Green frog (Rana clamitans)
  • Northern leopard frog (Rana pipiens)
  • Pickerel frog (Rana palustris)
  • Plains leopard frog (Rana blairi)
  • Southern leopard frog (Rana sphenocephala)
  • Spring peeper (Hyla crucifer)
  • Western chorus frog (Pseudacris triseriata)
  • Wood frog (Rana sylvatica)
section 18 2 modern evolutionary classification
Section 18.2 – Modern Evolutionary Classification
  • Traditional classification system is that scientists relied on body structure comparison
  • Organisms that are quite different from each other evolve similar body structures.
  • Ex: crabs, barnacles, and limpets
slide9

Traditional Classification vs. Evolutionary Classification

Appendages

Conical Shells

Crustaceans

Gastropod

Crab

Crab

Limpet

Limpet

Barnacle

Barnacle

Molted exoskeleton

Segmentation

Tiny free-swimming larva

CLASSIFICATION BASED ON VISIBLE SIMILARITIES

CLADOGRAM

evolutionary classification
Evolutionary Classification
  • Darwin’s ideas about descent with modification have given rise to the study of phylogeny, or evolutionary relationships among organisms. Used today.
classification using cladograms
Classification Using Cladograms
  • To refine the process of evolutionary classification, many biologists now use a method called cladistic analysis.
  • Uses derived characters – unique characteristics that appear in recent organisms.
cladograms
Cladograms
  • Derived characters can be used to construct a cladogram, a diagram that shows the evolutionary relationships among a group of organisms.
cladogram of animal kingdom
Cladogram of Animal Kingdom

Chordates

Echinoderms

Arthropods

Annelids

Mollusks

RadialSymmetry

Roundworms

Flatworms

Pseudocoelom

Deuterostome Development

Cnidarians

RadialSymmetry

Coelom

Protostome Development

Sponges

Three Germ Layers;Bilateral Symmetry

Tissues

Multicellularity

Single-celled ancestor

similarities in dna rna
Similarities in DNA & RNA
  • The genes of many organisms show

important similarities at the molecular

level. These similarities are used to

classify.

  • EX. Humans and yeast both have a gene that codes for myosin (a protein in our muscles) — an indicator that humans and yeast have a common ancestor.
dna evidence example
DNA Evidence Example
  • In the traditional classification system, African vultures and American vultures were classified together, but DNA analysis has revealed that American vultures are actually more closely related to storks.
  • Based on DNA analysis, we know

that chimpanzees are our closest

living relatives (humans and

chimps share 98.5% same DNA).

molecular clocks
Molecular Clocks
  • Comparisons of DNA can show how closely related organisms are.
  • A model known as a molecular clock uses DNA comparisons to estimate the length of time that two species have been evolving independently.
slide17

Neutral mutations (those that have no effect on phenotype) accumulate in the DNA of different species.

  • The more similar the neutral DNA (genes) the more closely related the organisms.
slide18
18-3 Kingdoms and Domains

The Tree of Life evolves

Linnaeus’s 2-kingdom classification was eventually revised to include 6 kingdoms: Eubacteria, Archaebacteria, Protista, Fungi, Plantae, and Animalia

slide19
The Three Domain System

Molecular analyses have given rise to a new taxonomic category called the Domain

Domain- a more inclusive category than any other—larger than a kingdom

1. Bacteria- corresponds to the kingdom Eubacteria

2. Archaea- corresponds to the kingdom Archaebacteria

3. Eukarya- corresponds to the kingdoms protists, fungi, plants, and animals

slide20
Domain Bacteria

Unicellular and prokaryotic

Thick, rigid cell walls with peptidoglycan (gram +)

Ecologically diverse (some are free-living while others are parasites, some need oxygen while others are killed by it)

Autotrophic or heterotrophic

EX. Streptococcus, E. coli, Syphilis, Chlamydia, etc.

slide21
DomainArchaea “ancient bacteria”

Unicellular and prokaryotic

Live in extreme environments (volcanic hot springs, black organic mud deprived of oxygen, and brine pools)

Cell walls lack peptidoglycan and cell membranes contain unusual lipids not found in any other organism (gram -)

Autotrophic or heterotrophic

EX. Methanogen, halophiles

slide22
Domain Eukarya

Consist of all organisms with a nucleus and is organized into the 4 remaining kingdoms

1. Protista

“taxonomic misfits” Don’t fit into other categories.

Most single-celled; some colonial, microscopic ¼ inch. Neither plant nor animal.

Some photosynthetic; others heterotrophic

Most Diverse Group- Amoeba (some cause dysentery; others harmless) paramecium, slimemolds (fungus-like), diatoms (plant-like), giardia (animal-like parasite), other diseases caused are sleeping sickness and malaria.

Sexual and asexual reproduction

slide23
2. Fungi

Produce foods such as

Cheese, soy sauce, mushrooms

Cell walls of chitin

Most multicellular; some

unicellular/ sexual and asexual reproduction

Heterotrophic—feed on dead organic matter (saprobes)

Fermentation to make alcohol

Produce antibiotics

Produce chemicals used in soaps and plastics

EX. mushrooms, yeast, potato blight, ringworm, mildew

slide24
3. Plantae

Cell walls of cellulose, Contain chloroplasts, Multicellular, Autotrophic, Nonmotile

Most are terrestrial and have adapted in the following ways:

Control water loss

Vascular tissue- move materials (Xylem-water and Phloem-food)

Protective packaging for gametes and embryos (pollen, eggs, seeds)

Ex: seed plants (angiosperms and gymnosperms) seedless plants (mosses, ferns, horsetails)

slide25
4. Animalia

Multicellular, Heterotrophic, lack cell walls

Great diversity and many species exist in nearly every part of the planet. Phylums listed below for Kingdom Animalia:

Phylum Porifera – sponges

Phylum Cnidaria – hydras, jellyfish, sea anemone, corals

Phylum Platyhelminthes – flatworms (planaria, flukes, tapeworms)

slide26
Phylum Nematoda – roundworms (nematodes)
  • Phylum Mollusca – mollusks (snails, squid, sea slugs, oyster)
  • Phylum Annelida- segmented worms (earthworms, leeches, marine)
  • Phylum Arthropoda – Insects, crustaceans, spiders, mites, millipedes, etc
  • Phylum Echinodermata- sea stars, sea cucumbers, sand dollars, brittle stars
  • Phylum Chordata- chordates or “vertebrates” during all or part of life (mammals, birds, reptiles, amphibians, fish, tunicates, etc.)
slide27

Key Characteristics of Kingdoms and Domains

Classification of Living Things

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

DOMAIN

KINGDOM

CELL TYPE

CELL STRUCTURES

NUMBER OF CELLS

MODE OF NUTRITION

EXAMPLES

Animalia

Eukaryote

No cell walls or chloroplasts

Multicellular

Heterotroph

Sponges, worms, insects, fishes, mammals

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

Eukarya

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

questions
Questions

1. How is a cladogram used?

2. How is a dichotomous key used?

3. How do you name organisms?