Chapter 17 Organizing Life's Diversity

Biological Classification 1. Provides a framework to study relationships among living & extinct species 2. Aids in identification -dichotomous key Dichotomous Notes Dichotomous Key Game

All Organisms and systems are organized from simple parts into complex systems that must maintain homeostasis in order to survive. Cells, tissue, organ, system, organism, population, community, ecosystem, Biosphere) How is life organized?

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.

Dichotomous Keys A dichotomous key is a tool that allows the user to determine the identity of items in the natural world based on the items characteristics "Dichotomous" means “divided into two parts” Greek origin dichotomous keys always give two distinct choices in each step, often they are opposites Black/white; good/evil; pointed/rounded

Here are creatures we don’t know! Lets choose one How to use a Dichotomous Key?

Choose only one creature at a time. How to use a Dichotomous Key?

Read steps 1a and 1b Decide which statement is true How to use a Dichotomous Key? 1b is true

Then follow the directions after that step. Go to step 5! How to use a Dichotomous Key? Because 1b is true we do what it says:

At choice 5, you make another dichotomous choice How to use a Dichotomous Key? G o t o s t e p 6 ! 5a is true

Keep going until you come to a step that gives you the creature’s name. C How to use a Dichotomous Key? 6 a. The creature has one antennae Go to Step 7.

start at step 1a and 1b Then, choose a new creature and start at step 1a and 1b again. Continue until you find the creature’s name. C How to use a Dichotomous Key? Where do you start Again?

Then, find the names of all the creatures (pssst, you don’t really need to do that…. )

Dichotomous key examples (Note the “2” statement format)

1. a. wings covered by an exoskeleton – go to step 2 b. wings freely observed – go to step 3 2. a. body has a round shape ……….ladybug, a red beetle with black spots b. body has an elongated shape ……….grasshopper, a green insect that hops 3. a. wings point out from the side of the body ……….dragonfly, an insect that is cm long and lives in marshes b. wings point to the posterior of the body ……….housefly, a flying insect with red eyes and an annoying buzz (Note the “2” statement format)

Now you will need to practice how to use a Dichotomous Key. You will need a clean sheet of paper to write your answers. First you will work with your 4 o’clock partner. Look at page 5 & 6 in your Packet and do the Salamander Dichotomous Key. Record your answers in your Packet. When you finish you can check your answers at Lab Station #1 Second look at page 7 & 8 in your Packet and do the Classify the State Dichotomous Key. Record your answers in your Packet. When you finish you can check your answers at Lab station #1.

Finally, you are going to create a Dichotomous Key. Look at page 9 in your Packet and READ the directions. Statements 1a & 1b are done for you to get you started. Rewrite those statements in the space below Figure 3, under “Key”, 1A & 1B. Don’t forget to put the number of the fish or “Go To Step…” Now, you create the other 3 statements to complete the Key. Your Homework will be identifying fish using a…., you guessed it!!, a dichotomous key. In case you haven’t figured it out, this will be on the test. (go to the next slide)

HOMEWORK: Go to page 11 & 12 and complete this Fish Dichotomous Key. This is due tomorrow (unless your teacher says otherwise).