Sorting It All Sorting It All OutOut

CLASSIFICATION!

Why Classify?Why Classify?

Classification: the division of Classification: the division of organisms into groups, or organisms into groups, or classesclasses, , based on specific characteristicsbased on specific characteristics

For thousands of years, humans have For thousands of years, humans have classified things based on classified things based on usefulnessusefulness

Biologists use system to classify Biologists use system to classify things—this system groups organisms things—this system groups organisms according to their according to their sharedshared characteristicscharacteristics

Classification of living things Classification of living things makes it easier for makes it easier for biologists to answer many biologists to answer many important questions, such important questions, such as:as:

How many known How many known species are there?species are there?

What are the What are the defining defining characteristics of characteristics of each species?each species?

What are the What are the relationshipsrelationships between between these species?these species?

How Do Scientists Classify How Do Scientists Classify Organisms?Organisms?

Great Greek Great Greek philosopher and philosopher and scientistscientist Aristotle (384-322 Aristotle (384-322 BCE) began BCE) began classifying classifying animalsanimals into into logical groupings logical groupings more than more than 20002000 years agoyears ago

– He arranged all He arranged all living things in an living things in an ascending ladder ascending ladder with with humanshumans at the at the toptop

– Animals were Animals were separated into separated into twotwo major groups—those major groups—those with red blood and with red blood and those without red those without red blood (very similar to blood (very similar to our modern our modern classification of classification of invertebrates and invertebrates and vertebratesvertebrates))

In 1700s, Swedish In 1700s, Swedish scientist Carolus scientist Carolus Linnaeus founded Linnaeus founded modern taxonomymodern taxonomy

TaxonomyTaxonomy:: the the science of science of describing, describing, naming, and naming, and classifying classifying organismsorganisms

Linnaeus tried to Linnaeus tried to classify all living classify all living things based on things based on their their shape and shape and structurestructure

– Species were Species were given distinctive given distinctive two-wordtwo-word namesnames

Described a Described a sevenseven-level -level system of system of classification, classification, which is still used which is still used today, although it today, although it has gone through has gone through many changes.many changes.

Classification TodayClassification Today

Taxonomists use the 7-level system to Taxonomists use the 7-level system to classifyclassify living things based on shared living things based on shared characteristicscharacteristics

Also use Also use sharedshared characteristics to characteristics to hypothesize how closely related living hypothesize how closely related living things arethings are

The more characteristics they share, The more characteristics they share, more closely related the organisms more closely related the organisms areare

Example: platypus, brown bear, lion, and house cat are thought to be related because they share many

characteristics. These animals have hair and mammary glands, so they are grouped together as mammals.

They can be further classified into more-specific groups.

Branching DiagramsBranching Diagrams Each characteristic on the Each characteristic on the lineslines of the branch are of the branch are

shared by the animals to the right of itshared by the animals to the right of it As you move As you move upup the line, the animals are more the line, the animals are more

closely related to each otherclosely related to each other

Levels of ClassificationLevels of Classification

Every living thing is classified into one of Every living thing is classified into one of six six kingdomskingdoms::

1.1. KINGDOMKINGDOM: : largest, most largest, most generalgeneral groupgroup

2.2. PHYLUMPHYLUM: sorted from the kingdom: sorted from the kingdom

3.3. CLASSCLASS: all living things in a phylum are : all living things in a phylum are sorted into classessorted into classes

4.4. ORDERORDER: each class includes one or more : each class includes one or more ordersorders

5.5. FAMILYFAMILY: one or more orders: one or more orders

6.6. GENUSGENUS: families are broken into genera: families are broken into genera

Genera are sorted into Genera are sorted into speciesspecies

A species is a group of A species is a group of organisms that are organisms that are closely related and can closely related and can mate to produce fertile mate to produce fertile offspringoffspring

Let’s see the Let’s see the classification of a classification of a housecat from kingdom housecat from kingdom Animalia to genus and Animalia to genus and species, species, Felis domesticusFelis domesticus

Kingdom AnimaliaKingdom AnimaliaAll animals are in the All animals are in the kingdom kingdom

animaliaanimalia

Phylum ChordataPhylum ChordataAll animals in the All animals in the phylum Chordataphylum Chordata have a have a hollow nerve cord. Most have a backbone.hollow nerve cord. Most have a backbone.

Class MammaliaClass MammaliaAnimals in the Animals in the class Mammaliaclass Mammalia have a have a backbone. They also nurse their young.backbone. They also nurse their young.

Order CarnivoraOrder CarnivoraAnimals in the Animals in the order Carnivoraorder Carnivora have a have a

backbone and nurse their young. They also backbone and nurse their young. They also have special teeth for tearing meat.have special teeth for tearing meat.

Family FelidaeFamily FelidaeAnimals in the Animals in the family Felidaefamily Felidae are cats. They have are cats. They have

a backbone, nurse their young and have special a backbone, nurse their young and have special teeth for tearing meat. The Felidae have five toes teeth for tearing meat. The Felidae have five toes on the front feet, four on the hind ones, all armed on the front feet, four on the hind ones, all armed

with strong "retractile claws”.with strong "retractile claws”.

Genus Genus FelisFelisAnimals in the Animals in the genus genus FelisFelis have traits have traits of other animals in the same family. of other animals in the same family.

However, these cats cannot roar; they However, these cats cannot roar; they can only purr.can only purr.

Species Species Felis domesticusFelis domesticusthe species the species Felis domesticusFelis domesticus is the is the common house cat. The house cat common house cat. The house cat

shares traits with all of the organisms shares traits with all of the organisms in the levels above the species level, in the levels above the species level,

but it also has unique traits.but it also has unique traits.

Scientific NamesScientific Names

A scientific name is always the same A scientific name is always the same for a for a specificspecific kind of organism no kind of organism no matter how many common names matter how many common names there might bethere might be

Before Linnaeus, different scientists Before Linnaeus, different scientists named organisms differently, so an named organisms differently, so an organism could have organism could have moremore than one than one namename Example on next slide…

Example:Example:

What do the mountain lion, cougar, and puma all have in common? They are ONE ANIMAL with several common names! The

scientific name for all three common names is Felis concolor, no matter where you go in

the world!

Two-Part NamesTwo-Part Names

Linnaeus simplified the naming Linnaeus simplified the naming of living things by giving each of living things by giving each species a two-part species a two-part scientificscientific namename

For example, the scientific name For example, the scientific name for the Asian elephant is for the Asian elephant is Elephas Elephas maximusmaximus. First part of name . First part of name ElephasElephas is genus name. Second is genus name. Second part, part, maximusmaximus, is species name., is species name.

No other species has both this No other species has both this genus name and species name.genus name and species name.

All genus names begin with All genus names begin with a a capitalcapital letter letter

All species names begin with All species names begin with aa lowercaselowercase letter letter

Usually, both words are Usually, both words are underlinedunderlined or or italicizeditalicized

Scientific names are usually Scientific names are usually in in Greek Greek or Latin, and or Latin, and contain information about contain information about the organismthe organism

Equus caballusEquus caballus

Dichotomous KeysDichotomous Keys

Dichotomous keyDichotomous key: an aid that is used to : an aid that is used to identify identify organisms and that consists of organisms and that consists of the answers to a series of the answers to a series of statementsstatements

There are only 2 alternative responses There are only 2 alternative responses to each statementto each statement

Either the chosen statement identifies Either the chosen statement identifies the organism or the person is directed the organism or the person is directed to another pair of statementsto another pair of statements

By working through By working through the statements in the statements in the key in the key in orderorder, , the person can the person can eventually identify eventually identify the organismthe organism

Dichotomous Key for Identifying Candy

A Growing SystemA Growing System

People are still discovering and People are still discovering and classifying organismsclassifying organisms

Some newly discovered organisms fit Some newly discovered organisms fit into existing categoriesinto existing categories

Sometimes, someone discovers new Sometimes, someone discovers new evidenceevidence or an organism is so or an organism is so different from other organisms that different from other organisms that it doesn’t fit into a category.it doesn’t fit into a category.