UNIT IVDIVERSITY OF LIVING

THINGSScientific Classification

CLASSIFICATION • the grouping of organisms by

similarities• Biological classifications are based

on how organisms are related.Group A Group B

Why Do We Classify Organisms?• Biologists group organisms to represent similarities and

proposed relationships.

• Classification systems change with expanding knowledge about new and well-known organisms.

Classification

• Binomial Nomenclature– Two part name (Genus, species)

• Hierarchical Classification– Seven Taxonomic Catagroies

• Systematics– Study of the evolution of biological diversity

Taxonomy: the branch of biology concerned with the grouping and naming of organisms; the study of classification

Taxonomy• Organisms are

classified into a hierarchy of groups and subgroups based on similarities that reflect their relationships over a period of time.

Cladogram or Phylogenic Tree

• A branching, treelike diagram in which the endpoints of the branches represent specific species of organisms.

• It is used to illustrate phylogenetic relationships and show points at which various species have diverged from common ancestral forms. Animation - Phylogenetic

Trees

Taxonomic Diagrams

Mammals Turtles Lizards and Snakes

Crocodiles Birds Mammals Turtles Lizards and Snakes

Crocodiles Birds

CladogramPhylogeneticTree

Biology: Samples -           

Tree of life

HISTORY: •Aristotle- developed the 1st

method of classification•He divided all living things

into 2 major groupsAristotle’s Groups

• He divided all living things into 2 major groups

• 1. Plants– classified by size and structure

2. Animals– classified by habitat (where they lived)

HISTORY: Aristotle

•Problems with his system:– Frogs live in both water and on

land

Bats, birds and flying insects were grouped together

• Kingdom – largest group

• Phylum (sing.) – Phyla (pl.)(Plants

don’t have phyla, they have divisions.)

• Class • Order • Family • Genus • Species

These two taxa make up the scientific name.

KingdomPhylum

ClassOrderFamilyGenusSpecie

s

K__________ p__________ c_________

o___________ f________ g_________ s________.

King Phillip came over for great soup.

HISTORY:

•Carolus Linnaeus- developed the modern system of classification

•Father of Taxonomy

Binomial Nomenclature

• Carolus von Linnaeus

• Two-word naming system– Genus

• Noun, Capitalized, Underlined or Italicized

– Species• Descriptive, Lower Case,

Underlined or Italicized

Binomial Nomenclature Binomial nomenclature is a

standard way of identifying a species with a scientific two-word name.

The first word is the genus name and the second the species name. Scientific name - 2 Latin names - Genus and species - Capitalize the first letter of the genus - Do NOT capitalize the species - ALWAYS underline or use italics

Ex. Homo sapiens

Binomial Nomenclature

Scientific Name: Homo sapiens

Common Name:

Albert Einstein

Binomial Nomenclature

Scientific Name: Rudbeckia hirta

Common Name: Gloriosa daisy

or Black-eyed Susan

Binomial Nomenclature

Scientific Name: Pinus virginianis

Common Name: Virginia Pine

Binomial Nomenclature

Scientific Name: Harmonia axyridis Common Name: Asian Ladybug

Binomial Nomenclature

Scientific Name: Ophiophagus hannahCommon Name: King Cobra

MODERN CLASSIFICATION SYSTEM

•Organisms are grouped together on the basis of: – Similarity in structure

Felis domesticusFelis rufusPanthera leo

Similarity in structure

Canis lupus

Similarity in structure

Canis latrans

Similarity in structure

Canis domesticus

Organisms are grouped together on the basis of:

• Similarity in genetic makeup (biochemistry)

• Similarities among organisms on the structural and metabolic levels are reflected in the large degree of similarity in proteins and nucleic acids of different organisms.

• Diversity is the product of variations in these molecules.

Organisms are grouped together on the basis of:

• Similarity of embryonic development

Evolution: Library: Common Past, Different Paths

Organisms are grouped together on the basis of:

• Similarity in evolutionary history

– Phylogeny: the evolutionary

history of a species based on comparing relationships between species using the fossil record

Organisms are grouped together on the basis of:

•Similarity in behavior

Systematics:Evolutionary Classification of Organisms

• Systematics is the study of the evolution of biological diversity, and combines data from the following areas.– Fossil record

– Comparative homologies

– Cladistics

– Comparative sequencing of DNA/RNA among organisms

– Molecular clocks

•Classification is based on close evolutionary relationships of organisms.

– Organisms classified in the same taxa (pl.) (taxon, sing.) share a common ancestry. They have evolved from the same common ancestral organism.

Evolutionary Relationships

• Classification is hierarchal

– each successive level is smaller and more closely related than the one before it

Species organisms that belong to the

same species can mate AND produce FERTILE offspring.

•Horses and donkeys can mate.– They produce a mule.

•Mules are INFERTILE

+ =

•Lions and tigers can mate.– They produce a liger.

•Ligers are INFERTILE

+ =

Why use scientific names?

• Common names do not indicate how organisms are related or classified.

Common names can be misleading.

(e.g., seahorse, weeping willow)

Organisms with more than one common name leads to mass confusion.

Why Latin?• Latin is no longer spoken, and

therefore, does not change as spoken languages do.

So, scientific names remain the same forever.