Chapter Intro-page 442 What Youll Learn You will identify and compare various methods of...

What You’ll Learn

You will identify and compare various methods of classification.

You will distinguish among six kingdoms of organisms.

• Evaluate the history, purpose, and methods of taxonomy.

Section Objectives:

• Explain the meaning of a scientific name.

• Describe the organization of taxa in a biological classification system.

• Biologists want to better understand organisms so they organize them.

• One tool that they use to do this is classification—the grouping of objects or information based on similarities.

How Classification BeganHow Classification Began

• Biologists who study taxonomy are called taxonomists.

How Classification BeganHow Classification Began• Taxonomy (tak SAH

nuh mee) is the branch of biology that groups and names organisms based on studies of their different characteristics. Click image to view movie.

• He classified all the organisms he knew into two groups: plants and animals.

Aristotle’s systemAristotle’s system

• The Greek philosopher Aristotle (384-322 B.C.) developed the first widely accepted system of biological classification.

• He grouped animals according to various characteristics, including their habitat and physical differences.

Aristotle’s systemAristotle’s system

• He subdivided plants into three groups, herbs, shrubs, and trees, depending on the size and structure of a plant.

• As time passed, more organisms were discovered and some did not fit easily into Aristotle’s groups, but many centuries passed before Aristotle’s system was replaced.

Aristotle’s system aka

Artificial Classification System

Aristotle’s system aka

Artificial Classification System

• According to his system, birds, bats, and flying insects are classified together even though they have little in common besides the ability to fly.

• Linnaeus’s system was based on physical and structural similarities of organisms.

Linnaeus’s system of binomial nomenclature


• In the late eighteenth century, a Swedish botanist, Carolus Linnaeus (1707-1778), developed a method of grouping organisms that is still used by scientists today.

• As a result, the groupings revealed the relationships of the organisms.

• This way of organizing organisms is the basis of modern classification systems.



• Eventually, some biologists proposed that structural similarities reflect the evolutionary relationships of species.

• In this system, the first word identifies the genus of the organism.



• Modern classification systems use a two-word naming system called binomial nomenclature that Linnaeus developed to identify species.

• A genus (JEE nus) (plural, genera) consists of a group of similar species.

• Thus, the scientific name for each species, referred to as the species name, is a combination of the genus name and specific epithet.



• The second word, which sometimes describes a characteristic of the organism, is called the specific epithet.

Homo sapiens

• Scientific names should be italicized in print and underlined when handwritten.

• Taxonomists are required to use Latin because the language is no longer used in conversation and, therefore, does not change.

• The first letter of the genus name is uppercase, but the first letter of the specific epithet is lowercase.

Passer domesticus

Scientific and common namesScientific and common names

• In addition, it is confusing when a species has more than one common name.

Scientific and common namesScientific and common names• Many organisms have

common names. However, a common name can be misleading. For example, a sea horse is a fish, not a horse.

• For example, biologists study the relationship between birds and dinosaurs within the framework of classification.

• Taxonomists group similar organisms, both living and extinct. Classification provides a framework in which to study the relationships among living and extinct species.

Archaeopteryx

Taxonomy: A frameworkTaxonomy: A framework

Taxonomy: A useful toolTaxonomy: A useful tool

• Classifying organisms can be a useful tool for scientists who work in agriculture, forestry, and medicine.

Taxonomy: A useful toolTaxonomy: A useful tool

• Anyone can learn to identify many organisms using a biological (dichotomous) key.

• A key is made up of sets of numbered statements. Each set deals with a single characteristic of an organism, such as leaf shape or arrangement.

Taxonomy and the economyTaxonomy and the economy

• It often happens that the discovery of new sources of lumber, medicines, and energy results from the work of taxonomists.

• The characteristics of a familiar species are frequently similar to those found in a new, related species.

Taxonomy and the economyTaxonomy and the economy

• For example, if a taxonomist knows that a certain species of pine tree contains chemicals that make good disinfectants, it’s possible that another pine species could also contain these useful substances.

How Living Things Are ClassifiedHow Living Things Are Classified

• In any classification system, items are categorized, making them easier to find and discuss.

• Although biologists group organisms, they subdivide the groups on the basis of more specific criteria.

• A group of organisms is called a taxon (plural, taxa).

Taxonomic rankingsTaxonomic rankings

• Organisms are ranked in taxa that range from having very broad characteristics to very specific ones.

• The broader a taxon, the more general its characteristics, and the more species it contains.


• The smallest taxon is species. Organisms that look alike and successfully interbreed belong to the same species.

• The next largest taxon is a genus—a group of similar species that have similar features and are closely related.

• Compare the appearance of a lynx, Lynx rufus, a bobcat, Lynx canadensis, and a mountain lion, Panthera concolor.

Lynx Mountain lionBobcat


Domain

Kingdom

Phylum

Class

Order

Family

Genus

Species

Eukarya

Animalia

Chordata

Mammalia

Carnivora

Felidae

Lynx

Lynx rufus

Lynx canadensisBobcatLynx

•Relationships are determined on the basis of similarities in structure, breeding, behavior, geographical distribution, chromosomes, and biochemistry.

How are relationships determined?How are relationships determined?

• Structural similarities among species reveal relationships.

Structural similaritiesStructural similarities

• The presence of many shared physical structures implies that species are closely related and may have evolved from a common ancestor.

• For example, plant taxonomists use structural evidence to classify dandelions and

sunflowers in the same family, Asteraceae, because they have similar flower and fruit structures.

Structural similaritiesStructural similarities

• Sometimes, breeding behavior provides important clues to relationships among species.• For example, two species of frogs, Hyla versicolor and Hyla chrysoscelis, live in the same area and look similar. During the

breeding season, however, there is an obvious difference in their mating behavior.

• Scientists concluded that the frogs were two separate species.

Breeding behaviorBreeding behavior

Geographical distributionGeographical distributionCrushing

Bills

Probing Bills

Grasping Bills

Ancestral Species

Parrot Bills

SeedFeedersC

actu

s

Fee

ders

Insect

Feeders

Fruit

Feeders

• These finches probably spread into different niches on the volcanic islands and changed over time into many distinct species. The fact that they share a common ancestry is supported by their geographical distribution in addition to their genetic similarities.

Geographical distributionGeographical distribution

• Both the number and structure of chromosomes, as seen during

mitosis and meiosis, provide evidence about relationships among species.

Chromosome comparisonsChromosome comparisons

Chromosome comparisonsChromosome comparisons• For example, cauliflower, cabbage, kale, and broccoli look different but have chromosomes

that are almost identical in structure.

• Powerful evidence about relationships among species comes from biochemical

analyses of organisms.

BiochemistryBiochemistry

• Closely related species have similar DNA sequences and, therefore, similar proteins.• In general, the more inherited nucleotide sequences that two species share, the more closely related they are.

Life’s Six KingdomsLife’s Six Kingdoms

• The six kingdoms of organisms are archaebacteria, eubacteria, protists, fungi, plants, and animals.

The Six Kingdoms of OrganismsThe Six Kingdoms of Organisms

• In general, differences in cellular structures and methods of obtaining energy are the two

main characteristics that distinguish among the members of the six kingdoms.

• The prokaryotes, organisms with cells that lack distinct nuclei bounded by a membrane, are microscopic and unicellular.

ProkaryotesProkaryotes

• Some are heterotrophs and some are autotrophs.

ProkaryotesProkaryotes• In turn, some prokaryotic autotrophs are chemosynthetic, whereas others are photosynthetic.

• There are two kingdoms of prokaryotic organisms: Archaebacteria and Eubacteria.

Ameoba

• There are several hundred species of known Archaebacteria and most of them live in extreme environments such as swamps, deep-ocean hydrothermal vents, and seawater evaporating ponds.

• Most of these environments are oxygen-free.


ProkaryotesProkaryotes• All of the other prokaryotes, about 5000 species of bacteria, are classified in Kingdom Eubacteria.

• Eubacteria have very strong cell walls and a less complex genetic makeup than found in archaebacteria or eukaryotes.


• They live in most habitats except the extreme ones inhabited by the archaebacteria.

• Although some eubacteria cause diseases, such as strep throat and pneumonia, most bacteria are harmless and many are actually helpful.

Staphylococcus

Protista: A diverse groupProtista: A diverse group

• Kingdom Protista contains diverse species that share

some characteristics.

• A protist is a eukaryote that lacks complex organ

systems and lives in moist environments.

Cilia

Oral groove

Gullet

Micronucleus and macronucleus

Contractile vacuole

Anal pore

A Paramecium

ProtistaProtista

• Although some protists are

unicellular, others are multicellular.

• Some are plantlike autotrophs, some are animal-like heterotrophs, and others are funguslike heterotrophs that produce reproductive structures like those of fungi.

Lycogala

Fungi: Earth’s decomposersFungi: Earth’s decomposers

• Organisms in Kingdom Fungi are heterotrophs that do not move from place to place.

• A fungus is either a unicellular or multicellular eukaryote that absorbs nutrients from organic

materials in the environment.

Fungi: Earth’s decomposersFungi: Earth’s decomposers

• There are more than 50,000 known species of fungi.

Plants: Multicellular oxygen producersPlants: Multicellular oxygen producers• All of the organisms in Kingdom Plantae are multicellular, photosynthetic eukaryotes.

• None moves from place to place.

Plants: Multicellular oxygen producersPlants: Multicellular oxygen producers

• A plant’s cells usually contain chloroplasts and have cell walls composed of cellulose.

• Plant cells are organized into tissue that, in turn, are organized into organs and organ systems.

• There are more than 250,000 known species of plants.

• Although you may be most familiar with flowering plants, there are many other types of plants, including mosses, ferns, and evergreens.

Plants: Multicellular oxygen producersPlants: Multicellular oxygen producers

Animals: Multicellular consumersAnimals: Multicellular consumers

• Animals are multicellular heterotrophs.

• Nearly all are able to move from place to place.

• Animal cells do not have cell walls.

Animals: Multicellular consumersAnimals: Multicellular consumers

• Their cells are organized into tissues that, in turn, are organized into organs and complex organ systems.

The Species and the Kind

• Linnaeus - first thought number of species was set at creation

– later thought they could change

• He and his students named about 10,000 plants and animals

Today

• There are now over 1.5 million known living species

• It is estimated that there are 5 to 10 million undiscovered

The Species

• The definition for species is not adequate

• Two things to consider when defining a species– Member of a species are structurally similar but do

have a degree of variation

– Members of a species can interbreed and produce viable and fertile offspring under natural conditions

Problems with Species Concept

• 1) Artificial characteristics

– environment can affect an organisms characteristics (ex - tiger salamander, Ambystoma tigrinum)

– a cross between two species makes a new combination, not a new species (ex - coyote + dog = coydog)

• 2) Interbreeding– Some species do not reproduce sexually

– Organisms of the same species may not necessarily be able to interbreed (St. Bernard and Chihuahua; the green spotted grass frog)

– ecotypes - organisms that appear the same but are suited for one environment and often cannot interbreed

• God’s primary purpose in creating different organisms was to have them perform specific functions in specific ways in specific places, not to make them easy to classify.

The Biblical Kind

• Organisms that reproduce after their own kind (Gen 1:20-25)

• Linnaeus was the first to use the term species (kind-latin)

• Some species can successfully interbreed making a hybrid organism – evoltion or not?

Natural System of Classification

• A system based on biochemical similarities

• Example - Humans, frogs, gorillas

• As researchers decode genomes they hope to show the relationships between organsims

Migration and Adaptation are not Evolution

• Migration - the moving of organisms from one area to another

• Adaptation - the change of an organism that allows it to survive in a new environment (limited to the organisms genetic makeup)

Which of the following is NOT a way to determine evolutionary relationships?

Question 1

D. geographical distribution

C. specific epithets

B. biochemistry

A. chromosome comparisons

C

How does a cladogram differ from a pedigree?

Question 2

Answer

Pedigrees show the direct ancestry of an organism from two parents. Cladograms show a probable evolution from an ancestral group.

Why do taxonomists use Latin names for classification?

Question 3

Answer

Latin is no longer used in conversation and, therefore, does not change.

What is the relationship between cladistics and taxonomy?

Question 5

Answer

Cladistics is one kind of taxonomy that is based on phylogeny.

• Although Aristotle developed the first classification system, Linnaeus laid the foundation for modern classification systems by using structural similarities to organize species and by developing a binomial naming system for species.

Classification

• Scientists use a two-word system called binomial nomenclature to give species scientific names.

• Classification provides an orderly framework in which to study the relationships among living and extinct species.

Classification

• Organisms are classified in a hierarchy of taxa: domain, kingdom, phylum or division, class, order, family, genus, and species.

• Biologists use similarities in body structures, breeding behavior, geographic distribution, chromosomes, and biochemistry to determine evolutionary relationships.

The Six Kingdoms

• Kingdoms Archaebacteria and Eubacteria contain only unicellular prokaryotes.

The Six Kingdoms

• Kingdom Protista contains eukaryotes that lack complex organ systems.

• Kingdom Fungi includes heterotrophic eukaryotes that absorb their nutrients.

• Kingdom Plantae includes multicellular eukaryotes that are photosynthetic.

The Six Kingdoms

• Kingdom Animalia includes multicellular, eukaryotic heterotrophs with cells that lack cell walls.

Domain

Kingdom

Phylum

Class

Order

Family

Genus

Species

Eukarya

Animalia

Chordata

Mammalia

Carnivora

Felidae

Lynx

Lynx rufus

Lynx canadensis

Bobcat Lynx

Question 1

Both organisms are members of the same kingdom, phylum, class, order, family, and genus but belong to different species.

Question 2

Which taxon contains the others?

D. family

C. genus

B. class

A. order

The answer is B.

Question 3

Which of the following pairs of terms is NOT related?

D. Aristotle – evolutionary relationships

C. biology – taxonomy

B. binomial nomenclature – Linnaeus

A. specific epithet – genus

The answer is D.

Domain

Kingdom

Phylum

Class

Order

Family

Genus

Species

Eukarya

Animalia

Chordata

Mammalia

Carnivora

Felidae

Lynx

Lynx rufus

Lynx canadensis

Bobcat Lynx

Question 4

Bobcats are more closely associated with lynxes as cats than as mammals.

Domain

Kingdom

Phylum

Class

Order

Family

Genus

Species

Eukarya

Animalia

Chordata

Mammalia

Carnivora

Felidae

Lynx

Lynx rufus

Lynx canadensis

Bobcat Lynx

Question 5

What two main characteristics distinguish the members of the six kingdoms?

The two characteristics are differences in cellular structures and methods of obtaining energy.

Question 6

Which of the following is NOT true of both the animal and plant kingdoms?

D. cells contain cell walls C. cells are organized into tissues

B. tissues are organized into organs A. both contain organisms made up of cells

D

Question 7

Which of the following describes a fungus?

D. heterotrophic prokaryote

C. unicellular autotroph

B. unicellular or multicellular heterotroph

A. autotrophic prokaryote

The answer is B, unicellular or multicellular heterotroph.

Question 8

What is the definition of a species?

Answer:

a group with members that resemble each other and that can interbreed to produce fertile offspring

Question 9

What is meant by the biblical kind?

Answer:

organism that reproduces after its own kind

Question 10

• What is a natural classification system?

Answer:

a system based on biochemical similarities

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