Dichotomous Key

Using Observable Characteristics

to Identify Objects

What is a dichotomous key?A dichotomous key is a tool that allows the user to

determine the identity of items in the natural world, such as trees, wildflowers, mammals, reptiles, rocks, and fish.

Keys consist of a series of choices that lead the user to the correct name of a given item.

"Dichotomous" means "divided into two parts". Therefore, dichotomous keys always give two choices in each step.

Using a dichotomous keyAt each step of the process of using the key, the user is

given two choices; each alternative leads to another question until the item is identified.

1a. If the leaves are flat….go to question 4. 1b. If the leaves are needle-like….go to question 2.2a. Are the needles in a bunch? Go to question 52b. Are they spread along the branch?“…pine tree

Eventually, when enough questions have been answered, the identity of the tree is revealed.

DICHOTOMOUS KEY EXAMPLE

1. a. tail fins are horizontal—whale………………….go to 2 b. tail fins are vertical—fish……………………….go to 32. a. has teeth or tusk—toothed whale………………..go to 4 b. has no teeth………………………...BALEEN WHALE3. a. has gill slits behind mouth—shark…….………...go to 5 b. has no gill slits……………………..NONSHARK FISH4. a. black with white underside………….KILLER WHALE b. tusk, gray with dark spots………………....NARWHAL5. a. head is hammer-shaped……..HAMMERHEAD SHARK b. tail is half the body length……….THRESHER SHARK

StartUse a dichotomous key to identify these individuals.

Pick an individual to identify, When you are ready click start.

Is the individual male or female?

Male Female

Is the individual wearing a hat?

Hat No Hat

Is the individual in the military?

Military Not Military

Is he wearing a dress uniform or a camouflage uniform?

Dress Uniform

CamouflageUniform

Introducing

He is a man wearing a hat and a military dress uniform.

Arnold

Return to Start

Introducing

He is a man wearing a hat and a camouflage military uniform.

Hector

Return to Start

Introducing

He is a man wearing a hat, but not wearing a military uniform.

Greg

Return to Start

Does the individual have facial hair or is he clean shaven?

FacialHair

CleanShaven

Is the individual wearing black?

WearingBlack

Not WearingBlack

What is the individual wearing?

Suit Jeans

Introducing

He is a man with facial hair, wearing a black suit, but not wearing a hat.

Reggie

Return to Start

Introducing

He is a man with facial hair, wearing a black shirt and jeans, but not wearing a hat.

Hugo

Return to Start

Introducing

He is a man with facial hair who is not wearing black or a hat.

Bill

Return to Start

What is the individual wearing?

Shorts Pants

Introducing

He is a clean shaven man who is wearing shorts, but not black or a hat.

Jack

Return to Start

Introducing

He is a clean shaven man who is wearing pants, but not black or a hat.

Kurt

Return to Start

Is the individual wearing a hat?

Hat No Hat

Is the individual wearing purple?

WearingPurple

Not WearingPurple

What is the individual wearing

Green Boaand Hat

Red Boaand Hat

Introducing

She is wearing a purple dress and green boa and hat.

Doris

Return to Start

Does the individual have a purse?

Purse No Purse

Introducing

She is wearing a purple dress and red purse, boa, and hat.

Erin

Return to Start

Introducing

She is wearing a purple dress and red boa and hat.

Rhonda

Return to Start

Introducing

She is wearing a hat, but not wearing purple.

Gail

Return to Start

What is the individual wearing?

Pants Skirt

Introducing

She is wearing pants, but not a hat.

Jenny

Return to Start

What color boots is the individual wearing?

Red Black

Introducing

She is wearing a skirt and red boots, but not a hat.

Mary

Return to Start

Introducing

She is wearing a skirt and black boots, but not a hat.

Beth

Return to Start

MAKING A DICHOTOMOUS CLASSIFICATION KEY

POSSIBLE“DERIVED CHARACTERS”

• All made of one material

• Is it hinged

• Has a sharp edge

• Has holes

• Hammer-like head

Hammer-like head Other types of head

Hammer-like head Other types of head

Hammer-like head Other types of head

ALL Made of Wood

Made of Wood and other materials

Hammer-like head Other types of head

Sides of head are different

Sides of headare same

Hammer-like head Other types of head

Sides of head are different

Sides of headare same

All wooden NOT all wooden

Hammer-like head Other types of head

Sides of head are different

Sides of headare same

All wooden Wooden and rubber? ?

Objects made of One Material Objects made of more than One Material

Divide the rest of the items until each one has been identified.