Chapter 17 Classification

Information from Holt Biology & other sites as listed

• Are you an organized person?– Consider – do you organize your room? CDs?

Your clothes? Your school work?

• What would happen if nothing was organized?– Would you be able to find anything?

• Why is it necessary to classify?

*Scientists have identified more than

2 MILLION SPECIES OF ORGANISMS- But estimate 40 MILLION SPECIES inhabit the Earth.

*There may be millions of undiscovered species, especially microbes, plants & insects , In the Tropical Rain Forest & Oceans

*Every year, thousands of new species are discovered.

I. Biodiversity• Biodiversity is the variety of organisms

on the earth.

• Considered at all levels from populations to ecosystems.

• Naturalists have invented several systems for categorizing

A. Taxonomy

• Taxonomy is the science of describing, naming, and classifying organisms.

• The branch of biology that names & groups organisms -according to their characteristics & evolutionary history.

• A Universal System was designed to Eliminate the use of Common Names and Confusion in the Scientific World.

History of Taxonomy

a. Aristotle –Early Classification system

• Greek philosopher more than 2,000 years ago

• Classified things- Plant or Animal– Grouped Animals into Land Dwellers, Water

Dwellers, and Air Dwellers. – Also grouped Plants into 3 categories, based

on differences in their Stems.

Naturalists replaced Aristotle’s classification system

• As modern science developed in the fifteenth and sixteenth centuries, Aristotle's system was found to be

INADEQUATE.

• Aristotle's categories did not work for all organisms.• his use of common names was problematic.

Use of Common Names• COMMON NAMES, such as “robin” or “fir

tree”, for organisms created some problems

• common names varied from one locale to next & did not describe species accurately.

• Use of long Latin names• Used by scientists before 1700’s,- did not

show relationships between species & were inconvenient, hard to understand.

Describe a problem with each of these common names

-Starfish -Seahorse -Jelly fish

-Peanut -Catfish -Tiger shark

How are their names misleading?

Discuss problems when 1 organism has 2 common names

Example- firefly & lightening bug

b. Carl Linnaeus (1707-1778)

“Father of Modern Taxonomy”

Swedish Naturalist• Used morphology(structure & form) • Grouped organisms into hierarchical categories

Linnaeus• Formed “Taxa” (groups of organisms)

• (Used Latin for the Names because it was the language of educated people)

• System was based on Morphology which are the STRUCTURAL SIMILARITIES BETWEEN ORGANISMS

• Series of hierarchical categories used to show relationships

• Linneaus divided organisms into 2 KINGDOMS:• PLANTAE & ANIMALIA.

• Then divided each Kingdom into smaller groups. (Linnaeus's classification hierarchy had 5 levels)KINGDOM, CLASS, ORDER, GENUS, SPECIES

• EACH LEVEL GROUPS TOGETHER ORGANISMS THAT SHARE MORE CHARACTERISTICS WITH EACH OTHER. (general to more specific)

Modern scientists add 2 more classifications levels to original 5: PHYLUM & FAMILY.

7 Modern Levels of Classification (From the most general to the most specific)

• Kingdom• Phylum• Class• Order• Family• Genus

• SpeciesSpecies is the smallest, most specific.Categories get larger, more general.

Kingdom is the largest, least specific

Pneumonic Devices• Keep Penguins Cool Or Find

Good Shelteror

• Kennywood Park Can Open For Good Summers.

or

• King Phillip Comes Over For Good Spaghetti

Classification Hierarchy of Organisms

3 Domains:

• Most modern system by Carl Woese

• These are Broad groups above the kingdom level.

Archaea

Bacteria

Eukarya

2. Binomial Nomenclature“Two name naming”

• Uses the last 2 categories (the most specific) to name things.

• Developed by Carl Linnaeus using the hierarchical system- uses the Genus & Species for the 2 parts of the name

• Always Capitalize the Genus but Not the Species Identifier. Both are either underlined or italicized.

Using Binomial Nomenclature• Acer rubrum - RED MAPLE TREE •   Acer is the Latin name for Maple (genus) •   rubrum is the Latin word for Red(species) •   Can be Abreviated: A.rubrum.

• HUMANS ARE NAMED: Homo sapiens • Homo -large brain & upright posture.

sapiens for our intelligence & ability

to speak. Abbreviated H. sapiens

Additional Categories

• Zoologists-use term “SUBSPECIES” for variations that may occur in species from different geographical locations- ie, timber wolf and the northern timber wolf-

Canis Lupus ssp occidentalis

• Botanists – May use the term “division” instead of phylum– sometimes split species into Subsets known as

VARIETIES. Example: peaches & nectarines are varieties of Prunus persica var.

• Microbiologists- Bacteria are also

broken into subsets called STRAINS. Example: Escherichia Coli – some strains are harmless, even helpful;- live in our intestines, but strain E. coli 157 is responsible for food poisoning deaths.

According to the CDC there are an estimated 73,000 cases of E. Coli infection every year in the United States. The typical symptoms are bloody diarrhea and (if severe) kidney failure. These symptoms most commonly appear when a person has eaten undercooked or contaminated ground beef.

  *The way we group organisms continues to change, and today these methods reflect the evolutionary history of organisms (What’s in their genes).

This is called Phylogeny.

II. Systematics

Systematics* organizes the diversity of living

organisms in the context of evolution.

Scientists construct Phylogenic Trees based on several types of evidence:

1. Fossil Record 2. Morphology3. Embryology 4. Chromosomes & Macromolecules

1. Phylogenic Trees

• A family tree that shows evolutionary relationships thought to exist among organisms.

• Is a hypothesis about the relationships.

• Is subject to change - as more evidence is learned.

1. Fossil Record• Fossil Record a useful tool for ancient

organisms. • Record is incomplete

– Some organisms overrepresented– Some organisms may be missing

• Need other evidences to verify phylogenic relationships

II. Shared ancestry: Evidences for Evolutionary Relationships

Fossils Types: actual preservation, petrification, imprints, molds, casts, footprints

• Dated by radioactive isotopes in fossil or geological formation in which fossils are found

• Requires long periods of time and unusual

conditions for fossil preservation

2. Morphology• Examine structure & function

• Homologous structures- similar features that originated from similar ancestors. (forelimbs on bat, human, penguin)

• Analogous structures- features that serve similar functions & look alike but originated from different embryonic tissues.

(wings- on butterfly, bat, hummingbird)

II. Shared ancestry: Evidences for Evolutionary Relationships

Homologous structures

Comparing the structural features found in different organisms reveals a basic similarity.

example is the forelimb of mammals - Although function is quite different, they are similar structurally.

Analogous structures• We must look at

structures that look & function the same but are not derived from the same embryonic tissue.

• These features do not show recent, related ancestory.

Vestigial structures• Features which serve no useful function any

longer in the organism.

• Examples: the pelvis bone in the whale, tailbone & appendix in humans, pelvis & leg bones in some snakes, etc

3. Embryology

• SIMILARITIES IN EARLY EMBRYOLOGICAL DEVELOPEMNT OF VERTEBRATES CAN BE TAKEN AS ANOTHER INDICATION THAT VERTEBRATES MAY SHARE A COMMON ANCESTRY.

II. Shared ancestry: Evidences for Evolutionary Relationships

At the blastula stage, scientists begin to look for differences in the ways organisms develop.

Blastula - An early embryonic form produced by cleavage of a fertilized ovum - a spherical layer of cells surrounding a fluid-filled cavity.(think of a basketball)

Gastrula - double-walled stage of the embryo succeeding the blastula; the outer layer of cells is the ectoderm and the inner layer differentiates into the mesoderm and endoderm

Embryology example-At the blastula stage- what happens if a scientist

separates a cell from the ball?

• In Vertebrates (animals with a backbone) &

Echinoderms animals like starfish & sand dollars)- any cell separated can produce a “twin”.

• But blastula cells in a fruit fly cannot- the separated cells are already specialized to form a part & will die.

• Conclusion- we are more closely related to starfish than insects

4. Chromosomes & Macromolecules

• Taxonomists compare Macromolecules like DNA, RNA & Proteins.

• Example- the number of differences in amino acids is a clue to how long ago 2 species “Diverged”

• In Divergent Evolution- 2 species become more and more dissimilar.

• Convergent Evolution- Species which have different ancestors, but have become more similar

II. Shared ancestry: Evidences for Evolutionary Relationships

Proteins indicate degree of relatedness. Differences - Amino Acids in Protein Cytochrome C

• (From Atlas of Protein Sequence and Structure, 1967-68 by Margaret O. Dayhoff

Number of different amino acids found in human cytochrome C as opposed to selected organisms

 Organism # of amino acids different compared to humans

Human 0 Self (Family Hominidae, Order Primates)

Monkey 1 Different family (Pongidae), same order (Primates)

Pig, bovine, sheep 10  Different order (Carnivora), same class (Mammalia)Horse 12

Dog 11

Rabbit 9

Chicken, Turkey 13 Different class (Aves), same phylum (Chordata) - homeothermicDuck 11

Rattlesnake 14 Different class (Reptilia), same phylum (Chordata) - poikilothermicTurtle 15

Tuna 21 Different class (Ostheichthys), same phylum (Chordata) - poikilothermic

Moth 31 Different phylum (Arthropoda), same Kingdom (Animalia)

Candida fungus 51 Different Kingdom (Fungi)

Martin (1993).

B. Cladistics• uses shared, derived characters as

the only criterion for grouping taxa.

• is a newer way to display relationships which highlights other differences (shared or derived chracters)

• Shared characters-

• Derived Characters- are special features that apparently have only developed in that group

– like feathers in birds

Cladogram• Shared derived characters are strong

indicators of common ancestry.

• Diagrams which show derived characters are called cladograms.

• Cladograms can show non-traditional conclusions about

which organisms

are “close cousins”.

From this cladogram, we can figure out that brown bears have more derived characters in

common with sun bears than with dogs & lesser pandas are more closely related to

racoons than giant pandas.

Cladogram

Dichotomous Key

• A dichotomous key graphically organizes data. You start with a main idea, split that into two major pieces. Those pieces are then split again into two major pieces. You can continue splitting each piece until you reach only one possible answer.

• Each set of questions is called a couplet, & contains instructions for which couplet to go to next.

Example of Dichotomous Key

Dichotomous Key Use• Can be used by any one to classify anything.• Are used by taxonomists to classify organisms.

III. TWO MODERN SYSTEMS OF CLASSIFICATION

 Aristotle classified organisms as either plant or animal, but today we recognize that many forms of life are neither

2 Ways to organize (things continue to change)

A. Three Domain System

B. Six Kingdom System

Modern TAXONOMY recognizes that many organisms are Neither

Plant or Animal. • Study cellular structure

• Look at ways organisms obtain food:

–Autotroph- Makes own food (photosysthesis or chemosynthesis)

–Heterotroph- Eats something

3 Domain System• Compares Ribosomal RNA of different

organisms.• Most modern system by Carl Woese• Broad groups

ArchaeaBacteriaEukarya

3 Domains1. Archaea = Prokaryotic cells

2. Bactaeria = Prokaryotic cells

3. Eukarya = Eukaryotic cellsThere are four kingdoms in Eukarya* Protista * Fungi* Plantae * Animalia

• SIX KINGDOMS GROUP ORGANISMS TOGETHER THAT HAVE SIMILARITIES SUCH AS MAJOR CELLULAR STRUCTURE, METHODS OF OBTAINING NUTRIENTS, AND METABOLISM.

The 3 Domains in detail:• Domain Archaea

– aligns with Kingdom Archaebacteria, are single-celled prokaryotes that have distinctive cell membranes and cell walls.

• Domain Bacteria– aligns with Kingdom Eubacteria, are single-

celled prokaryotes that are true bacteria.

• Domain Eukarya– Domain Eukarya includes the kingdoms Protista,

Fungi, Plantae, and Animalia. – All members of this domain have eukaryotic cells.

What are Bacteria?

• Until recently, the term bacteria was used for all microscopic prokaryotes. But, it turns out that there are two groups of prokaryotes that differ from each other in just about every way except size and lack of a nucleus.

• These are now divided into 2 kingdoms: – Archaea -(also known as Archaebacteria)

anicient, extreme environments.– Bacteria- the "true" bacteria (also known as

Eubacteria)

Domain: Archaea & Bacteria

Bacteria-

• Organisms in the Kingdoms Eubacteria & Archae are very different from each other.

• Archaebacteria have been found in temperatures above the boiling point and in cold that would freeze your blood. Eubacteria are the “regular” bacteria.

Domain: Archaea & Bacteria

1. Archeabacteria• The prefix archae - comes from the Greek Word

"ANCIENT".  MAY BE Directly descended from and very similar to the First Organisms on Earth. 

• They Are UNICELLULAR PROKARYOTES with distinctive Cell Membranes as well as Biochemical and Genetic Properties that Differ from ALL Other Kinds of Life. 

• Some are AUTOTROPHIC, producing food by CHEMOSYNTHESIS. Most are HETEROTROPHIC. 

Domain: Archaea, Kingdom Archeabacteria

Archaea:

• Some types are

• A. Methanogens

• B. Themoacidophiles

• C. Extreme Halophiles

Domain: Archaea, Kingdom Archaeabacteria

• Called Extremophiles• Many Archaebacteria LIVE in HARSH

ENVIRONMENTS such as Sulfurous Hot Springs, Very Salty Lakes, and in ANAEROBIC Environments, such as the Intestines of Mammals. Includes Chemosynthetic Bacteria.

Domain: Archaea, Kingdom Archaeabacteria

The “true” bacteria• The first thing you probably think of

when you say this word is “disease”- something like strep. throat or maybe an infection in a cut.

• Most of the bacteria that are disease causing are Eubacteria.

• NOTE: Only about 1% of bacteria are disease causing.

Domain: Bacteria, Kingdom Bacteria

• Many bacteria are very helpful organisms.

• Actinomycetes, produce antibiotics such as streptomycin and nocardicin;

• others live symbiotically in the guts of animals (including humans) or elsewhere in their bodies, or on the roots of certain plants, converting nitrogen into a usable form.

• Bacteria put the tang in yogurt and the sour in sourdough bread;

• help to break down dead organic matter; & make up the base of the food web in many environments.

Domain: Bacteria, Kingdom Bacteria

The true or “Eubacteria”

• UNICELLULAR PROKARYOTES (No true nucleus)

• Are the greatest number of living things on earth.• No membrane bound organelles• Circular double strand of DNA

• “Eu” means true. Eubacteria are the common, true bacteria- causing strep throat, food poisioning, tooth decay, fermenting milk into yogurt, etc.

Domain: Bacteria, Kingdom Bacteria

Classifying bacteria:

• Bacteria occur in 3 basic shapes: cocci, bacilli & spiral. Many are named by their shape.

Domain: Bacteria, Kingdom Bacteria

3. Protists• Made of a variety of organisms that don’t

“fit” anywhere else. Some are not very much like the others in this group.

• EUKARYOTIC (has a true, membrane bound nucleus)

• 50,000 species- many unicellular, some are like fungi, some like plants or animals.

• Includes protozoans, unicellular algae, slime molds & water molds

Domain: Eukarya, Kingdom Protista

Protists includes slime molds & protozoans like Euglena, Paramecium, Ameoba

4. Fungi

• Unicellular & multicellular• HETEROTROPHIC (eats something

else)

–NOT like plants (photosyntheic)

100,000 species include mushrooms, puffballs, rusts, mildew & molds

Domain: Eukarya, Kingdom Fungi

5. Plantae • Multicellular & Photosynthetic

Autotrophs (food by photosynthesis) They are the chief producers of the world.

• Found in all the types of environments: aquatic algae, amphibian mosses, and terrestrial ferns and seed-bearing plants.

• 350,000 species identified.

Domain: Eukarya, Kingdom Plantae

6. Animalia

• Eukaryotic, Multicellular Heterotrophic organisms.

• Most animals are symmetrical

• Movement at some time in their life cycle.

Domain: Eukarya, Kingdom Animalia