TEXTBOOK: From Bacteria to Plants

Chapter One: Living ThingsSection 3 “Classifying Organisms.” Pg. 28-37

Classifying Organisms

Why do Scientists Classify?

There are 2.5 million kinds of organisms on Earth. (including plants, animals and bacteria)

Classification

• —the process of grouping things based on their similarities.

We classify • foods “dairy, meat, poultry, fruit,

vegetables.”

We classify music “rap, r&b, pop, country”

Early Classification Systems

Aristotle—

came up with the idea to use observations to classify animals by appearance, behavior, movement

Fly     Swim     Walk, crawl run

Populus tremuloides

Quaking Aspen

Classification and Phylogeny

• Binomial Nomenclature

• Hierarchical Classification

• Systematics: Evolutionary Classification

Carolus von Linnaeus(1707-1778)

Swedish scientist who laid foundation for modern taxonomy

• Carolus von Linnaeus

• Two-word naming system

– Genus

• Noun, Capitalized, Underlined or Italicized

– Species

• Descriptive, Lower Case, Underlined or Italicized

Binomial Nomenclature

The Classification System of Linnaeus

Used observations as the basis of his system.

Binomial nomenclature

• each organism was given a two part name. Made of a genus and species name that identifies a certain organism.

Genusfirst part of name. A classification grouping

that contains similar, closely related organisms.

Species

2nd part of name. A group of similar organisms that can mate and produce fertile offspring in nature.

Latin

genus and species names are in Latin language. This was the language all scientists communicated in.

Italics and Capitalization

the complete scientific name is written in italics. The genus name is capitalized while the species name begins with a small letter. Example: Felis domesticus—house cat/ domestic cat

Organisms

are grouped by their shared characteristics. First put in a broad group and then moved into more specific groups

Hierarchical Classification• Taxonomic categories• 7 Levels of Classification

– Kingdom King

– Phylum Philip

– Class Came

– Order Over

– Family For

– Genus Green

– Species Soup

The more classification levels that two animals share, the more characteristics they have in common.

Evolution and ClassificationCharles Darwin published a theory about how

species change over time.

It is proven that species can change over time (adaptations).

Ex. Humans get taller,

Ex. Bird’s beak gets more pointed.

It is not proven that organisms can change into other species,

ex. A monkey into a person

Evolutionthe process by which species gradually

change over time.

Classification Today

Theory is that species are similar because they share a common ancestor.

Species with similar evolutionary histories are classified more closely together. i.      Get information about how species used to be from fossils

Compare body structures and chemical makeup to fossils.

c. Compare body structures to other organisms

d. Compare early development of different organisms.

• Ex. Humans and rabbits go through similar stages in their development before birth.

This means they may share evolutionary history.

• Primarily rely on info about the chemical makeup of cells to determine evolutionary history. The more closely related the 2 species, the more similar the chemicals that make up their cells are.

chemical makeup of cells

Using the Classification System

Taxonomic Key—a series of paired statements that describe the physical characteristics of different organisms.

Taxonomic Diagrams

Mammals Turtles Lizards and Snakes

Crocodiles Birds Mammals Turtles Lizards and Snakes

Crocodiles Birds

CladogramPhylogeneticTree

MONEY TAXONOMIC KEY 1 A. Metal....................................................go to 2 1 B. Paper....................................................go to 5

2 A. Brown (copper)........................................penny 2 B. Silver....................................................go to 3

3 A. Smooth edge...........................................nickel. 3 B. Ridges around the edge...............................go to 4

4 A. Torch on back..........................................dime 4 B. Eagle on back...........................................quarter

5 A. Number 1 in the corners...............................$1 bill 5 B. Number 2 in the corners...............................$2 bill

Now, try to make your own taxonomic key (similar to the money taxonomic key). Make your key separate out each of

the 5 kingdoms. Remember to use pairs of contrasting statements.

Possible Answer (your answer may vary)

Dichotomous Keys Identify Organisms

• Dichotomous keys versus evolutionary classification

• Dichotomous keys contain pairs of contrasting descriptions.

• After each description, the key directs the user to another pair of descriptions or identifies the organism.

Identifying a leafExample:

1. a) Is the leaf simple? Go to 2b) Is the leaf compound? Go to 3

2. a) Are margins of the leaf jagged? Go to 4

b) Are margins of the leaf smooth? Go to 5

Identifying aninsect