How to use a Dichotomous key & practice

Dichotomous Key

By Ashley Nieves

What is a dichotomous key?

A tool-

It is used by scientist to identify and classify new organisms

• Start with the first organism

• Read the first steps

• Decide which statement is true and follow the directions.

• The directions will lead you to a new pair of choices.

• Keep doing this until you come to a step that gives you the organisms name.

• Choose the next organism and repeat these steps.

• Do this until you identify every organism.

How do you use a dichotomous key?

• Start with the first organism

• Read the first steps

• Decide which statement is true and follow the directions.

• The directions will lead you to a new pair of choices.

• Keep doing this until you come to a step that gives you the organisms name.

• Choose the next organism and repeat these steps.

• Do this until you identify every organism.

Let's Practice...

Hotspot

Click on the first organism and the first step.

Multiple Choice

If the wings of organism A are not covered by an exoskeleton, what step do you go to next?

• step 2

• step 3

• step 1b

• step 3a

• Start with the first organism

• Read the first steps

• Decide which statement is true and follow the directions.

• The directions will lead you to a new pair of choices.

• Keep doing this until you come to a step that gives you the organisms name.

• Choose the next organism and repeat these steps.

• Do this until you identify every organism.

Let's Practice...

Multiple Choice

Which statement is true about organism A?

Step 3:

3a- wings point outward from the body- dragonfly

3b-Wings point toward the rear of the body- bee

• 3b

• 3a

• Start with the first organism

• Read the first steps

• Decide which statement is true and follow the directions.

• The directions will lead you to a new pair of choices.

• Keep doing this until you come to a step that gives you the organisms name.

• Choose the next organism and repeat these steps.

• Do this until you identify every organism.

Let's Practice...

Multiple Choice

What is the name of organism A?

• ladybug

• firefly

• dragonfly

• bee

Complete the knowledge check and practice dichotomous key questions on the following slides.

Multiple Choice

When using a dichotomous key- what step do you always start with?

• the last step

• any step

• the first step

• the step in the middle

Multiple Choice

True or false:

You should start with first organism.

• True

• False

Multiple Choice

True or false:

Once you identify an organism you repeat the steps to identify the next organism.

• True

• False

Multiple Choice

Start with Organism A-

From step one which statement is true?

• Needle leaves- go to step 2

• non-needle leaves - go to step 3

Multiple Choice

Step 3:

Which statement tis true about organism A?

• Simple leaves (single leaf)- go to step 4

• Compound leaves (made of "leaflets")- go to step 7

Multiple Choice

Step 4:

Which statement is true about organism A?

• Smooth edged- go to step 5

• Jagged edge- go to step 6

Multiple Choice

Step 5:

Which statement is true about organism A?

• Leaf edge is smooth - Magnolia

• Leaf edge is lobed - White Oak

Labelling

Using the dichotomous key-

Identify organisms B-H.

Label each leaf with the correct name.

Drag labels to their correct position on the image

Holly

Walnut

Chestnut

Pine

White Oak

Spruce

Elm