Classification of Living Things Classification is the arrangement

Classification of Living Things

• Classification is the arrangement of organisms into groups based on their similarities. • Taxonomy: the science of describing, naming, and classifying organisms

Why do we bother to classify things? It allows us to make sense of the huge number of living things in the world.

Early classification • Aristotle grouped everything into simple groups such as animals or plants • He then grouped animals according to if they had blood or didn’t have blood, and if they had live young or laid eggs, and so on…

• All organisms are classified into three domains.

Modern Taxonomy The Evidence used to classify into taxon groups – 1) Embryology – 2) Chromosomes / DNA – 3) Biochemistry – 4) Physiology – 5) Evolution – 6) Behavior

Levels of Classification » DOMAIN » Most general: Kingdom » Phylum » Class » Order » Family » Genus » Most specific: Species

Helpful way to remember the 8 levels • Dumb kids playing catch on freeways get squashed • Or…make up your own… – D K P C O F G S

Every living thing has a unique two-part scientific name = Binomial Nomenclature

Binomial Nomenclature • Developed by Carolus Linnaeus • Swedish Biologist 1700’s • Two-name system • Genus and species named using Latin or Greek words

Rules used to write scientific names Homo sapiens • An organism’s genus is always written first; the organism’s species is always written second • The genus is Capitalized; the species is written in lower case • Scientific names of organisms are always italicized or underlined

For example: Tyrannasaurus rex • Genus species

• Scientific names are usually in Greek or Latin. Therefore, scientists all over the world are sure they are talking about the same living organism.

Cladograms

• Cladogram – diagram that shows the evolutionary relationships between organisms • Derived characters - traits or characteristics that have evolved – Individual organisms “branch off” when they do not share the derived character in question

Feathers

Let’s try this… • Cladograms can be constructed for any group of organisms. – kangaroo, earthworm, amoeba, lizard, cat, sponge, and salmon. • Each of these creatures has an evolutionary relationship to one another.

• They all share a common origin. • their current forms are all derived from branching events somewhere in the phylogenetic past.

Complete the characteristic chart • Use + to indicate the presence of a characteristic in the organism • Use – to indicate that the organism does not have the characteristic segmented Derived Characters kangaroo earthworm amoeba lizard cat sponge Salmon jaws hair placenta Multicellular limbs

earthworm kangaroo

amoeba lizard

cat sponge

salmon

Derived Characters segmented jaws hair Kangaroo 5 + + + - - + + + + + - Earthworm 2 Amoeba 0 lizard cat sponge Salmon placenta Multicellula r limbs

Ok • Look at the organisms to see how many of the derived characters they share: – Amoeba has 0 – Sponge has 1 – Salmon has 3 – Etc.

• Using these patterns of shared derived characters, a cladogram can be constructed as a series of branches. • At every branch, one of the organisms that does not share a common character with the rest of the group is "branched off" into its own clade.

cat sponge salmon earthworm lizard kangaroo amoeba

cat sponge salmon earthworm lizard kangaroo amoeba

cat salmon earthworm lizard kangaroo sponge amoeba ll ce ti ul M

cat salmon earthworm lizard kangaroo earthworm sponge amoeba d te en gm Se lle ce ti ul M

cat kangaroo salmon earthworm sponge ws Ja amoeba lizard gm Se d te lle ce ti ul en M

cat kangaroo lizard salmon earthworm bs m Li sponge ws Ja amoeba gm Se lle ce d te ti ul en M

cat kangaroo lizard salmon earthworm H r ai sponge bs m Li ws Ja amoeba gm Se lle ce d te ti ul en M

cat kangaroo lizard H r ai sponge bs m Li ws Ja amoeba ta en ac Pl salmon earthworm gm Se lle ce d te ti ul en M

A Dichotomous Key A tool to identify similarities and differences in organisms is the : Taxonomic Key (Dichotomous Key) -paired statements that describe the physical characteristics of different organisms

Taxonomic Key 1 a Fruits occur singly. . . Go to 3 1 b Fruits occur in clusters of two or more. . . . Go to 2 2 a Fruits are round. . . . Grapes 2 b Fruits are elongate. . . Bananas 3 a Thick skin that separates easily from flesh. . Oranges 3 b Thin skin that adheres to flesh. . . . Go to 4 4 a More than one seed per fruit. . . . Apples 4 b One seed per fruit. . . Go to 5 5 a Skin covered with fuzz. . . . . Peaches 5 b Skin smooth, without fuzz. . . . Plums What steps would you use to identify an apple?