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Change Through Time

Classification

Organizing Life’s Diversity

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

• One tool that they use to do this is classification

• Classification is 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 is the

branch of biology that groups and names organisms based on studies of their different characteristics.

• 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 systemAristotle’s 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 nomenclatureLinnaeus’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.

Linnaeus’s system of binomial nomenclatureLinnaeus’s system of binomial nomenclature

• 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.

Linnaeus’s system of binomial nomenclatureLinnaeus’s system of binomial nomenclature

• Binomial nomenclature is a modern classification system using a two-word naming system that Linnaeus developed to identify species.

• A genus is 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.

Linnaeus’s system of binomial nomenclatureLinnaeus’s system of binomial nomenclature

• A specific epithet is the second word, which sometimes describes a characteristic of the organism

Homo sapiens

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

• 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

Scientific and common namesScientific and common names• Taxonomists are required to

use Latin because:

1. the language is no longer used in conversation and, therefore, does not change

2. a common name can be misleading.

3. it is confusing when a species has more than one common name.

• Grouping organisms on the basis of their evolutionary relationships makes it easier to understand biological diversity.

Modern ClassificationModern Classification

• Expanding on Linnaeus’s work, today’s taxonomists try to identify the underlying evolutionary relationships of organisms and use the information gathered as a basis for classification.

• 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

• Anyone can learn to identify many organisms using a 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.

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.

Taxonomic rankingsTaxonomic rankings

• 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

Taxonomic rankingsTaxonomic rankings

Domain

Kingdom

Phylum

Class

Order

Family

Genus

Species

Eukarya

Animalia

Chordata

Mammalia

Carnivora

Felidae

Lynx

Lynx rufus

Lynx canadensis

Bobcat Lynx

Most Inclusive to Least InclusivePlace the following groups in the appropriate level: Mammals, Man, Primates, Vertebrates, Animals

AB

CD

E

Most Inclusive to Least InclusiveAdd the following groups to the appropriate level on the Venn Diagram: Kingdom Plantae, Division Angiospermae, All Organisms, Order Rodentia, Tulip, Kingdom Animalia

A

B

CD

EF

Most Inclusive to Least InclusiveComplete the Venn Diagram with the following groups: Family Vespidae (yellow jacket), Phylum Arthropoda, Order Lepidoptera (butterflies), Class Insecta, Order Hymenoptera (bees, wasps)

A

BC D

E

Most Inclusive to Least InclusiveDraw a Venn Diagram to represent the following groups:

Kingdom Animalia

Class Osteichthyes (Bony Fish)

Phylum Chordata (animals with backbones)

Class Chondrichthyes (Cartilaginous Fish)

Family Sphyrnidae (Hammerhead Shark)

Question 1

How did Aristotle group organisms such as birds, bats, and insects?

D. by their homologous structures

C. by their common species

B. by their analogous structures

A. by their common genus

The answer is B. The organisms were grouped together because of their wings, which, in this case, are analogous structures.

Question 2

Which taxon contains the fewest species?

D. phylum

C. order

B. family

A. genus

The answer is A, genus.

Question 3

For which of the following species names does the specific epithet mean “handy?”

D. Homo habilis

C. Australopithecus anamensis

B. Homo erectus

A. Homo sapiens

The answer is D.

Question 4

What is the difference between “classification” and “taxonomy?”

AnswerClassification is the grouping of objects or information based on similarities. Taxonomy is the branch of biology that classifies and names organisms based on their different characteristics.

Question 5

What are the two parts that make up binomial nomenclature?

Answer

Binomial nomenclature comprises a genus name followed by a specific epithet.

1. Put these animals into 3 groups.

2. What characteristics did you use for your system of classification?

Change Through Time

The Six Kingdoms

Organizing Life’s Diversity

• Classification systems today are based on evolutionary relationships.

•This means extinct animals can also be included in classification schemes.

How are evolutionary relationships determined?How are evolutionary relationships determined?

• Evolutionary relationships are determined on the basis of:

•similarities in structure

•breeding behavior

•geographical distribution

•chromosomes

•biochemistry

How are evolutionary relationships determined?How are evolutionary relationships determined?

• 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

Chromosome comparisonsChromosome comparisons• For example, cauliflower, cabbage, kale, and

broccoli look different but have chromosomes that are almost identical in structure.

• Therefore, biologists propose that these plants are related.

• 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.

• Phylogeny is the evolutionary history of aspecies

Phylogenetic Classification: ModelsPhylogenetic Classification: Models

• A classification system that shows the evolutionary history of species is a

phylogenetic classification and reveals the evolutionary relationships of species.

• Cladistics is a biological system of classification that is based on phylogeny.

CladisticsCladistics

• Scientists who use cladistics assume that as groups of organisms diverge and evolve

from a common ancestral group, they retain some unique inherited characteristics that taxonomists call derived traits.

• A cladogram is a branching diagram used to identify a group’s derived traits; it is a model of phylogeny of a species

CladisticsCladistics

• Cladograms are hypothetical evolutionary trees.

CladisticsCladistics

Theropods

Allosaurus

Sinornis

Velociraptor

Archaeopteryx

Robin

Light bones 3-toed foot; wishbone

Dry scales

Feathers withshaft, veins,and barbs

Flight feathers;arms as long

as legs

• Organisms are assigned to a group on a cladogram by a unique characteristic they share in common with other members of that group.

• A derived character is a unique trait, such as dry skin, that is used to assign an organism to a group.

CladisticsCladistics

• One type of model resembles a fan.

Another type of modelAnother type of model

• A fanlike model may communicate the time organisms became extinct or the relative

number of species in a group.

• A fanlike diagram incorporates fossil information and the knowledge gained

from anatomical, embryological, genetic, and cladistic studies.

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 (eat other organisms) and some are autotrophs (make their own

food).

ProkaryotesProkaryotes

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

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

• Archaebacteria live in extreme environments such as swamps, deep-ocean hydrothermal

vents, and seawater evaporating ponds.

• Most of these environments are oxygen-free.

ProkaryotesProkaryotes

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.

ProkaryotesProkaryotes

• 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.

Protists: A diverse groupProtists: 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

Protists: A diverse groupProtists: A diverse group

• 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.

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

eukaryotic, multicellular, photosynthetic autotrophs.

• 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.

Fold two vertical sheets of paper in half from top to bottom.

To return to the chapter summary click escape or close this document.

Turn both papers horizontally and cut the papers in half along the folds. Discard one of the pieces.

To return to the chapter summary click escape or close this document.

Fold the three remaining vertical pieces in half from top to bottom.

To return to the chapter summary click escape or close this document.

Turn the papers horizontally. Tape the short ends of the pieces together (overlapping the edges slightly) to make an accordian book.

To return to the chapter summary click escape or close this document.

Tape

Label each fold with the name of one of the six kingdoms.

Put characteristics of each kingdom under its heading.

To return to the chapter summary click escape or close this document.

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

The answer is 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.

Using the cladogram, which of the following traits would be a primitive trait?

Question 3

Theropods

Allosaurus

Sinornis

Velociraptor

Archaeopteryx

Robin

Light bones 3-toed foot; wishbone

Down feathers

Feathers withshaft, veins,and barbs

Flight feathers;arms as long

as legs

Question 3

Theropods

Allosaurus

Sinornis

Velociraptor

Archaeopteryx

Robin

Light bones 3-toed foot; wishbone

Down feathers

Feathers withshaft, veins,and barbs

Flight feathers;arms as long

as legs

A. down feathers B. arms as long as legs C. light bones D. flight feathers

The answer is C. Primitive traits are traits that evolved very early.

Theropods

Allosaurus

Sinornis

Velociraptor

Archaeopteryx

Robin

Light bones 3-toed foot; wishbone

Down feathers

Feathers withshaft, veins,and barbs

Flight feathers;arms as long

as legs

Why do taxonomists use Latin names for classification?

Question 4

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.

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?

Answer

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

The answer is 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 a dichotomous key?

Answer

A dichotomous key is a set of paired statements that can be used to identify organisms.

Question 9

How has DNA-DNA hybridization shown that flamingoes are more closely related to storks than they are to geese?

When DNA from storks and flamingoes was allowed to bond, DNA base pairs matched and the strands bonded more strongly than when DNA from flamingoes and geese was allowed to bond.

FlamingoStork