|Ocean Creature Classification
In this activity, students will learn about the scientific
classification of organisms and compare their own classification of a group of organisms
to the scientifically accepted one.
At the conclusion of the lesson, students will be able to:
- use observed similarities and differences to develop their own system
for classifying a group of objects or organisms
- understand the process of scientific classification, and explain how
marine organisms are classified by scientists
Time: 2 periods
The oceans surrounding Eleuthera are rich with life. In particular,
the coral reefs and mangrove forests are home to an astounding array of animals, plants,
and other organisms. In order to help identify these organisms and understand their
evolutionary relationships, scientists have developed a system for classifying organisms
with similar characteristics. When scientists classify an organism, they look closely at
the structure of its body. They also examine the way that it develops as an embryo and,
more recently, its DNA. All these factors provide clues about the relationships of
different organisms. On the broadest level, animals (Kingdom Animalia) are classified by
scientists as either vertebrates (with backbones) or invertebrates (without backbones).
All vertebrates belong to the same phylum (Chordata), but invertebrates belong to several
different phyla. Members of a particular phylum are further subdivided by class, order,
family, genus, and, finally, species. In general, the greater the number of classification
levels that two organisms have in common, the more characteristics they share.
Scientists employ taxonomic keys to identify and help classify
organisms. Organisms are classified by identifying differences in a series of steps. At
each step, the remaining organisms must be split into two and only two possibilities. For
example, if the first characteristic chosen is color, red and not
red would be acceptable choices, but red and blue would not
be since there are additional colors that are not included in the latter groups.
Once classified, scientists give each animal or species a unique
scientific name that consists of two Latin words: the first is the animals genus
name, the second is its species name. For example, the scientific name of the spiny
lobster is Panulirus argus. Scientific names of organisms can be found in any field guide.
An organisms common name may vary from country to country or even within the same
country, but its scientific name is universally recognized by scientists around the globe,
Since students are likely to be most familiar with vertebrates, this
activity focuses on the classification of marine invertebrates. The table below shows
invertebrate organisms commonly found in the coral reefs surrounding Eleuthera.
barrel sponge, finger sponge, glassy sponge, white slipper sponge, brown sponge, orange
sponge, vase sponge
pink-tipped anemone, zoanthid, sea fan (soft coral), cannonball jellyfish, Portuguese
man-o-war, hard coral
long-spined sea urchin, sea star, sea cucumber, brittle star, sand dollar, feather star
magpie shell, clam, oyster, mussel, scallop, sea snail, sea hare, cuttlefish, octopus
||green reef crab,
spiny lobster, cleaner shrimp, mantis shrimp
worm, purple fan worm, Christmas tree worm
The example used in Steps 1 and 2 of the following procedure is
students shoes, but any group of readily available objects that share some but not
all characteristics would work as well. For Step 3, photographs or drawings of various
invertebrates are available in field guides or on the web (see the Resources section at
the end of this guide for possible sources). You may also wish to consider classifying
local organisms of interest in place of tropical marine invertebrates.
Elementary: Steps 1 and 2 are appropriate. If used,
Step 3-4 should be simplified somewhat by reducing the number of organisms and including
only the most obvious examples.
Middle School and High School: Students should be able
to complete all steps. Without the key, students are unlikely to exactly match the
scientific taxonomy by simply examining drawings or photographs, as scientists have
additional information not evident from the drawings. Stress that the process that the
students are using is the same as that used by scientists as they attempt to classify a
group of organisms. As a clue to students, you may wish to tell them how many organisms
from each phylum are included in their sample.
Ecology, invertebrate, taxonomic key
Steps 1 and 2: overhead projector,
transparency, set of similar but not identical common objects (e.g., shoes, shells); Step
3: copies of invertebrate drawings or photographs (unlabeled), taken from a coral
reef field guide and/or the web, Ocean Invertebrates Taxonomic Key (provided)
- Introduce students to the process of scientific classification by
having them develop their own taxonomic key for classifying a group of common
objects-shoes. Have the class gather in a circle and have each student donate one of the
shoes that they are wearing to a pile at the center of the circle. Tell students that the
class as a whole will be developing a method for classifying shoes and that the method you
will be using is the same as that used by scientists to classify and/or identify
- Next, ask students to suggest different ways that the pile of shoes
could be classified. Some likely answers include: left/right; black/not black;
has laces/no laces; sneaker/not sneaker; shiny/dull; and so forth. Have students vote on
which characteristic to select first. Have them divide the pile of shoes into two piles,
according to whether each shoe does or doesnt have that characteristic. Next, have
students choose a second characteristic, and divide each of the two piles of shoes into
two piles, according to whether each shoe has that second characteristic (thus making a
total of four piles). Keep on in this manner until each shoe is eventually placed in its
own unique pile. Then, reconstruct the exercise using a diagram on an overhead
transparency, showing each chosen characteristic on the diagram. You have now created a
taxonomic key for shoes.
- Have students work in small groups to practice scientific
classification while becoming familiar with some of the common types of organisms that
inhabit a typical coral reef. Provide each group with photographs or drawings of between
1215 marine invertebrates, being sure to include at least 1 from each of the
following phyla: Porifera, Cnidaria, Echinodermata, Mollusca, Annelida, and Arthropoda.
Consult the table in the Background section for sample organisms. After students have
sorted the various organisms using their own criteria, review their results in a whole
class discussion, asking each group to explain their reasoning.
- Have students repeat Step 3, this time using the provided Ocean
Invertebrates Taxonomic Key that illustrates the scientifically accepted classification
for such organisms according to phyla. Have students compare their results from Step 3
with their results using the key, noting any differences.
Extend the Experience
Choose an ecosystem in your local region, such as a pond, field, or
woodland. Through library, online and/or outdoor research, try to find the common and
scientific names of at least five plant and animal species that are commonly found in that