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Dichotomous Keys

7.11A examine organisms or their structures and use dichotomous keys for identification

ESSENTIAL QUESTION:How can you use dichotomous keys to classify and identify organisms?

OBJECTIVES:1. Dichotomous Keys Tree Leaves Sort2.“Aliens” Activity with Dichotomous Keys (HW)

Vocabulary

Dichotomous Key - Terms1. Variation (or Variability): differences

among traits or characteristics of an organism.

2. Species: a group of organisms that are able to successfully reproduce.

3. Dichotomous Key: A tool used in plant or animal identification. It is a series of questions, and each question is a choice between two characteristics. You can find the organism’s identity through the process

Purpose of Keys

To classify organisms

External Structures

Imagine that you have two species of birds.

Working with a partner, list what external structures you might use to identify whether or not they are the same species.

Write your list on the white board

Dichotomous Key Example

DO-NOW

Now lets focus on the external structures of a plant.

What are some possibilities?

Look at these plant varieties

Identifying TreesUse your “Trees of Texas” handout, and the

color card set.

Work with your partner to identify the trees by looking at the external characteristics of the leaves.

When done, check with me before moving on.

Identifying Aliens - HW

Using your handout, follow the clues on the front in order to identify the correct name of the alien species.

Check for understanding!

• I will show you a set of pictures in a minute.

• When you see the images, think about which characteristics you might use to identify these organisms

• Also think about which ones would be useless!

Myzia interrupta Delphastus pusillus Brachiacantha barberi

Olla v-nigrum Neoharmonia venusta

Dichotomous Keys