Classification

Chapter 18

Key Concepts

•How living things are organized for study

•What dichotomous classification is

•What binomial nomenclature is

•What Linnaeus’s system of classification is

18-1 Interest Grabber 1. Consider the task facing early biologists who

attempted to organize living things. How might they have begun?

2. Suppose that you have been given a green plant, stringy brown seaweed, a rabbit, a mushroom, a worm, and a grasshopper. You’ve been asked to organize these things into categories that make sense. How would you do it?

3. Decide on your categories and write each on a sheet of paper. Next to each category, write the defining characteristics of that category. Then, write in the organisms that fall into each category.

18–1 Finding Order in Diversity

Why Classify?

Assigning Scientific

Names

Early efforts at

naming organisms

Binomial

nomenclature

Linnaeus’s System of Classification

Kingdom

Phylum

Class

Order

Family

Genus

Species

Q: What is this animal called?

•Confusing common

names

• Panther

• Puma

• Mountain Lion

• Catamount

• Cougar

A: All of the Them! •Common Name depending on location

• Panther

• Puma

• Mountain Lion

• Catamount

• Cougar

•Scientific Name • Puma concolor

(formerly Felis concolor – changed in 1993)

Note – in Scientific Name, only the first term is capitalized

Section 18-1

Kingdom

Phylum

Class

Order

Family

Genus

Species

Linnaeus’s System of

Classification

You need to know these!

Think of a mnemonic

device to help you

remember the order!

“Please Excuse My Dear

Aunt Sally”

“King Phillip Cuts Open

Five Green Snakes”

Choose something that

has meaning to you

“Kings Play Colorado On

Friday. Go! Score!”

Section 18-1

Kingdom

Phylum

Class

Order

Family

Genus

Species

Linnaeus’s System of

Classification

Kingdom – a group of related phyla

**Linnaeus only recognized two kingdoms

– Plant & Animal**

Phylum – a group of related classes

Class – a group of related orders

Order – a group of related families

Family – a group of related genera

Genus – a group of related species

Species

Scientific name is always “Genus species”

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

Classification

of

Ursus arctos

What are some

ways in which

these animals are

similar, and what

are some ways

they are different?

What are some

ways in which

these animals are

similar, and what

are some ways

they are different?

18-2 Interest Grabber One Big Family?

How can you determine if one organism is closely related to another? It may seem easy, but it isn’t, and looks are often deceiving. For example, roses and orchids are both flowering plants, but roses grow on bushes or vines and have thorns. Many orchids don’t even grow in soil—they can grow in trees! Rose and orchid blossoms look very different, and roses and orchids cannot produce hybrids, or offspring of crosses between parents with different traits.

18-2 Interest Grabber Do you think roses and orchids are closely

related? Explain your answer.

Now, apply the same logic to dogs. Different breeds of dogs—such as a Labrador retriever and a collie—can breed and produce offspring. So what is the difference between the rose-orchid combination and the Lab-collie combination?

What defines a species? Is appearance important? What other factors might be considered?

18-2 Modern Evolutionary

Classification

Which Similarities Are Most Important?

Evolutionary Classification

Classification Using Cladograms

Similarities in RNA and DNA

Molecular Clocks

CLADOGRAM

Appendages Conical Shells

Crab Barnacle Limpet Crab Barnacle Limpet

Crustaceans Gastropod

Molted

exoskeleton

Segmentation

Tiny free-swimming larva

Section 18-2

CLASSIFICATION

BASED ON VISIBLE

SIMILARITIES

Traditional Classification

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 vs. Cladogram

18-3 Interest Grabber

My Way or the Highway

Categories that are used to organize an

assortment of things should be valid. That is,

they should be based on real information.

However, categories should be useful, too.

Suppose that you are taking a survey of

traffic. You sit at the side of a busy

intersection and record the vehicles you

see in one hour.

18-3 Interest Grabber

What categories could you use to

organize your count of vehicles?

Look at your list of categories. Are all of

them equally useful?

Is there more than one valid and useful

way to organize living things?

18-3 Kingdoms and Domains

The Tree of Life Evolves

The Three Domain System

Domain Bacteria

Domain Archaea

Domain Eukarya

Protista

Fungi

Plantae

Animalia

Section 18-3

are characterized by

such as

and differing which place them in

which coincides with which coincides with

which place them in which is subdivided into

Living Things

Kingdom

Eubacteria Kingdom

Archaebacteria

Eukaryotic

cells Prokaryotic cells

Important

characteristics

Cell wall

structures

Domain

Eukarya

Domain

Bacteria

Domain

Archaea

Kingdom

Plantae

Kingdom

Protista

Kingdom

Fungi

Kingdom

Animalia

Cladistic Analysis Analysis of the order in

which derived

characteristics appeared

Cladogram – diagram that

shows the evolutionary

relationships among a

group of organisms based

on these characteristics

Derived Characteristics – a

characteristic that arises as

a lineage of organisms

evolves over time

DNA analysis determined evolutionary relationships

Similar genes are evidence of common ancestry

American Vultures and Storks are classified together based on DNA

Molecular Clocks Comparison of DNA -

determines when species diverged and began to evolve independently

“Neutral mutations” – insignificant genetic changes that accumulate at a steady rate are measured and compared from species to species

The degree of disimilarity indicates how long ago the two species shared a common ancestor

5 Kingdom

Classification

Monera – bacteria,

prokaryotes

Protista – unicellular, animal or plant like, such as algae

eukaryotes

Fungi – mushrooms

Eukaryotes, *previously classified as plants*

Plantae

eukaryotes

Animalia

eukaryotes

Six Kingdoms Monera Kingdom is too

general and composed of two distinct groups of bacteria Differences are as great

as those between animals and plants

Six Kingdom classification system separates monera into two kingdoms: Eubacteria Archaebacteria Protista

Fungi Plantae Animals

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

Key Characteristics of

Kingdoms & Domains

Three Domain System Classifications and divisions are based on evidence from

molecular clock models Organisms are grouped according to how long they

have been evolving independently (1) Domain Bacteria – Corresponds to Kingdom

Eubacteria unicellular, prokaryotes, peptidoglycan (protein that gives strength to the cell

wall; also important in binary fission (cell reproduction) (2) Domain Archaea – Corresponds to Kingdom

Archaebacteria unicellular, prokaryotes; live in the most extreme

conditions (low to no O2, brine pools, and volcanic hot springs)

No peptidoglycan; contain unusual lipids not found in any other living organisms

Three Domain System (cont.) (3) Domain Eukarya – all organisms that

have a nucleus (eukaryotes) Protista – members have greatest

variety, single celled and multi-cellular, some P/S like algae, some heterotrophic

Fungi – Heterotrophs, feed on dead or decaying matter, multicellular mushrooms and unicellular yeasts

Plants – multicellular P/S organisms, cell walls contain cellulose

Animals – multicellular heterotrophs, no cell walls

Kingdoms Eubacteria

Archaebacteria

Protista

Plantae

Fungi

Animalia

DOMAIN

EUKARYA

DOMAIN

ARCHAEA

DOMAIN

BACTERIA

Cladogram of Six Kingdoms &

Three Domains