Biology

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Part 1: The assignment document contains a table with nine images. The images are examples of nine different Animal phyla: Porifera, Cnidaria, Nematoda, Arthropoda, Platyhelminthes, Annelida, Mollusca, Echinodermata, and Chordata.DownloadU5IP_Table.Next, Download Dichotomous KeyUse the Dichotomous Key to determine the Class category as shown for each animal (picture), and write the Class names under the Classification Column on the table.List in column 2, all of the dichotomous key steps you chose when using the key to arrive at the classification for each animal.You will also need to list the Phylum name for each animal picture in column one using the nine Phyla listed above. Once you have identified the Class category for each animal using the Key, look up the correct Phylum category using a credible reference.  

1. For help on how to use the Dichotomous Key, download and review the document called How to Use the Dichotomous Key.

HOW TO USE A DICHOTOMOUS KEY

Dichotomous means ‘divided or cut into two parts’. A dichotomous key is a tool used by
scientists to classify organisms into categories. The key is made up of a series of
categories, and within each category are two opposing statements called couplets.

To use the key, you always start at the first category (look for a ‘1’ in the first column).
Read the two statements ( labeled ‘a’ and ‘b’ in the second column) and consider them
carefully. If you do not know the meaning of a word, as some of these terms are
technical, look it up (www.dictionary.com is a great site).

Now, look at your organism. Choose the statement (a or b) that best fits your organism.
All parts of the statement must be true. (Here’s an example: If your organism has an
irregular shape, it must also have pores.) At the end of the statement you will come to a
word or a number.

If you come to a word or phrase you have found the phylum, class or genus that
your organism belongs to, and you are finished identifying the organism!

If the true statement has a number at the end, go to that category (skip all the
others) and read the couplet (a and b statements) you find there.

Again, you would choose the statement that best describes a characteristic of your
organism, and follow the number to the next couplet. Continue until you come to the
classification of your organism.

Here’s an example: Lobster

Category 1:

a) Irregular-shaped body; structure with many pores — Phylum Porifera

b) Regular-shaped body (with right and left halves or a cylindrical shape) — 2

The funny thing about scientists is that they have a language all their own. So an
‘irregular shape’ really means something with no clear, recognizable shape. A blob is a
good example. A ‘regular shape’ on the other hand, means anything with a recognizable
shape. It could be round or square, or shaped like something you’ve seen often; a star or
a fish or a dog, for example. The lobster has a regular shape (it looks like a lobster,
crayfish, or insect) and it has right and left sides, so choose statement b and go to
Category 2.

Here are the statements for Category 2:
a) Radial symmetry (disk-shaped or barrel-shaped) — 4
b) Bilateral symmetry (similar right and left body halves) — 3
You may want to look up the terms radial and bilateral. Radial means having rays like the
sun or a daisy. Bilateral means having two sides. The lobster is not shaped like a star
or disk, it is bilaterally symmetric, so go to Category 3.
a) Animal has internal skeleton — 19
b) Animal has external skeleton or no apparent skeleton — 6
The lobster has an external skeleton — its shell. If you are not sure about a
characteristic of the organism, you could use www.google.com to help you determine if

a statement is true or false. For example, you could look up the key words ‘lobster’ and
‘skeleton’. You will find sites that describe the lobster’s exoskeleton. Go to Category 6:
a) Hard outer covering — 6
b) No hard outer covering — 7
A lobster’s shell is hard, go to Category 10.
a) Body has jointed legs — 14
b) Body inside shell is soft, has no jointed legs — 13
Even though the body inside the shell is soft (and delicious), the lobsters legs are jointed
so the second part of statement b is false. Since the legs are jointed you would choose a,
and go to Category 14.
a) Jointed appendages on most body sections — 15
b) Jointed appendages on certain body segments; not all appendages are legs —
16
Even though it looks like there jointed appendages on most of the sections of the lobster,
it also has antennae and claws, so not all the appendages are legs, choose statement b,
and go to Category 16
a) Two pairs of antennae, large claws often present — Class Crustacea.
b) One pair of antennae or none, no large claws — 17.
The lobster has large claws — Class Crustacea!

Present your work in this format: List the name or organism number, then each of
the numbers for each step of the key, then the class or phylum of the organism.

The key for a lobster is:

1b, 2b, 3b, 6a, 10a, 14b, 16a, Class Crustacea.

This way you demonstrate that you used the key, and you can get partial credit even if
you ended up at the wrong answer.

Unit

5

Individual Project

Name:

Date:

Part

1

. There are

9

animals in nine different Phyla. Be sure to look at every page.

Animal	Phylum	Dichotomous Key (steps)	Classification
1
2
3
4
5
6
7
8	Image Rights: Allen G. Collins and the UC Museum of Paleontology
9	Image Rights: Courtesy of University of Minnesota

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