Invertebrate Zoology
Lab Unit 1 - General Diversity
Descriptive characteristics for a given taxon may be
helpful in distinguishing these groups. However many
important characteristics that are used to define these
taxa are internal, cellular, developmental, or even
molecular. In addition, external morphologies of
different phyla can some times be strikingly similar due
to convergent evolution while those of taxa within a phylum may be quite
different (this is one reason that later on in the semester we must use
taxonomic keys to make identifications). The goal of the exercise outlined
here is to expose you to some common representatives of some of the major
groups, and to begin to examine these patterns of invertebrate diversity.
Questions to consider as you work through the phyla:
Are there certain external morphologies that work well across distantly
related phyla?
Are there certain basic overall body plans that work well resulting in
diversity of external morphologies within some phyla?
Do phyla on the same phylogenetic branch of the tree share obvious
similarities?
As you examine the specimens, make any notes in your journal that might
help you remember the specimens for the practical. This might include
short written descriptions or drawings of distinguishing parts. This portion
of your notebook will due at the time of the lab practical.
For the lab practical,
 Be able to identify the specimen (taxonomic name) marked with the
asterisk for each of the phyla or class. (~70% of the exam practical)
 Be able to answer the question listed for each phylum. The questions
refer to the external morphologies of the specimens in lab. You may
use your lecture textbook to help. (~20% of the exam practical)
 Be able to consider both of the above to identify new specimens not
previously observed in lab (~10% of the exam practical)
Porifera (sponges)
What morphological characteristic is common to all displayed
specimens within this phylum and helpful in distinguishing it from
other phyla on display?
Cnidaria (jellyfish, anemones, corals, etc.)
Describe variations in other specimens within this phylum
(some of these other specimens are actually the extra-cellular matrix
of a colony of individuals; e.g. the coral rock):
Ctenophora (comb-jellies)
Note rows of ciliated ‘combs’
How is symmetry of the body different than in most of the other
invertebrates on display?
Platyhelminthes (flatworms)
What characteristic distinguishes this phylum of worms from the
other worm-shaped phyla on display?
Mollusca (snails, clams, squids, etc.)
For this phylum, I also want you to know some of the major classes:
Class Gastropoda
Class Bivalvia
Class Cephalopoda
What morphological characteristic is common to all displayed
specimens within this phylum?
Annelida (segmented worms)
For this phylum, I also want you to know some of the major classes:
Class Polychaeta
Class Clitella
Is segmentation of the body unique to phylum?
Sipuncula (sipunculids)
How is this specimen similar to annelids? (Note: members of this
phylum have an eversible anterior body part but in this preserved
specimen it is retracted forming a puckered opening).
Brachiopoda (brachiopods)
What taxon do these appear most similar to in terms of external
morphology and are they closely related? (Note: internally they are
very different possessing lophophore feeding structure)
Bryozoa (moss animals)
In these specimens, you are looking at a colony of animals that secrete
a gelatinous matrix. Take a look under the scope at these. What
other phylum has members that are colonial and secrete a matrix?
Arthropoda (insects, spiders, crabs, etc.)
For this phylum, I also want you to know some of the major classes:
Class Arachnida
Class Crustacea
Class Insecta
Class Myriapoda
What morphological characteristic is common to all displayed
specimens within this phylum and helpful in distinquishing it from
other phyla on display?
Onychophora (velvet worms)
How is this specimen different than Arthropods? (Hint: look closely
at the legs)
Nematoda (round worms)
Which phylum appears to be most similar to this one?
Nematomorpha (horsehair worms)
Chaetognatha (arrow worms)
Use the scope to observe the lateral stabilizing fins.
Echinodermata (starfish, urchins, sea cucumbers, etc.)
Describe variations in other specimens within this phylum.
What morphological characteristics are common to all displayed
specimens within this phylum?
Hemichordata (hemicordates)
Does this specimen’s external morphology suggest a close evolutionary
relationship to chordates (the phylum to which we belong) and to
echinoderms?
Chordata (vertebrates and relatives)
For this phylum, I also want you to know some of the major subphyla:
Subphylum Urochordata
Subphylum Cephalochordata
Subphylum Vertebrata
Describe variations in other specimens within this phylum.
What morphological characteristic is common to all subphyla within
this phylum? Is this characteristic apparent in all life stages?