Lab - Phylogenetics, Protozoa, Porifera

Thursday, January 19, 2012

A radial phylogenetic tree of life
(version of the tree found in Life: the Science of Biology [9th edition]
by Sadava, Hillis, Heller, and Berenbaum)

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PHYLOGENETICS

In this lab students learned how to approach classifying the diversity of invertebrate animals based on evolutionary relationships rather than in overall morphological similarity. The main approach to do so was by examining the most basic concepts of phylogenetics by using cladistics as a tool.

They did a small exercise in which a character data matrix was completed, by observing a variety of specimens of several invertebrate phyla, and used to generate a cladogram.  By doing so, some of the difficulties that systematists have to face became obvious, and students attempted to solve them with a variety of approaches.

Thursday, January 26, 2012

PROTOZOA AND PORIFERA

Amoeba proteus, a protozoan

Spicules from a sponge

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Preserved specimens from the main groups of protozoans were observed under the microscope for students to identify their main morphological features:

Ciliates: Spirostomum, Vorticella, Didinium, Stentor, Paramecium
Flagellates: Trichonympha, Euglena, Volvox, Trypanosoma, Ceratium
Ameobeoids: Amoeba, Foraminifera, Radiolaria, Actinosphaerium

Preserved specimens of the various classes of the phylum Porifera (click here for more sponges) were displayed for students to observe their general morphology.  Some specimens ere available to be treated with commercial bleach to dissolve the organic matter and observe the spicules of different individuals. By using polarizing filters students were able to determine if the spicules were calcareous or siliceous.

Observed specimens belonged to the classes:

• Calcarea
• Demospongiae
• Hexactinellida

See the filtering activity of sponges

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Lecture - Phylogeny and Protozoa

Choanoflagellate (left), and colony

Traditional Metazoan Phylogeny

January 11 - 27, 2012

So far we have introduced the main animal phyla that we will cover in this course, introduced the basic concepts of cladistics and overall evolutionary view of diversity ("tree thinking"), and we have studied the most basic features of the Protozoa the informal (not taxonomically valid) grouping of protists that have "animal-like" characteristics.

Among the Protozoa, we considered some of the major groups, following the traditional (more like ancient) classification. The current classification has shifted to reflect evolutionary relationships, but in the scope of this class the traditional groupings will suffice.  The groups we considered were the flagellates, the ciliates, and the amoeboeoids.

The flagellates are of special interest since some of its representatives, the choanoflagellates, are considered, mostly based on molecular evidence, as the sister group of metazoa (more metazoa), and probably very similar to our last common ancestor.
We discussed the traditional metazoan phylogeny, and mentioned that the "new" metazoan phylogeny will be discussed over the course of the semester (it's not that new any more).

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Welcome to Invertebrate Zoology (Biol 2231)

Wednesday, January 11, 2012

Welcome to Invertebrate Zoology (Biol 2231)!

This course will examine the diversity of invertebrate organisms, focusing on major animal phyla (most of “the other 95%”).  Topics under study will include the origin and evolution of diversity, the evolutionary relationships among invertebrate taxa, and the functional biology of invertebrates.  To address these topics, this course will cover the anatomy, physiology, developmental biology, evolution,  and ecology of the major phyla in both lecture and lab.  Along the way you will develop an appreciation for the great diversity of invertebrate animals on this planet and their importance for the ecosystem and in our everyday lives.   


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