'97-'98
Classification Lab

Old Classification Lab

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Classification Lab
Purpose

To learn how to identify and classify animals by various criteria.

What is Classification?

The classification of organisms is the attempt by biologists to arrange organisms in categories and groups that reflect phylogeny -- the evolutionary history of a group of organisms. There are two types of classification, cladistic and classic. Cladistic classification is concerned only with the order of branching in phylogenetic lingeages. It uses cladograms, which are a serious of branches that divide at homologous features, to classify subjects. The homologous features come in two types, primitive characteristics, that already exsisted in the phylogeny, and derived characteristics, which are homologous features that are unique to the common ancestor. In classic classification, taxonomists use degrees of divergence in lineages to classify.

Our Classifications

By kingdom:

Algae Algae Kingdom
Fungi Kingdom
Monera Kingdom
Plantae Kingdom
Protista Kingdom
Animalia


Conclusion

To conclude our Classification Lab we were asked to, by our teacher, to answer a few questions about the differences in the animal line, here they are:

The first division is between Parazoa and Eumetazoa.
Parazoa is a division of animal line which includes only sponges, everything else is Eumetazoa. The difference between the two is that Parazoans have no true tissue, in fact, you can push them through a filter or screen and their cells will join back up up at the other side.

The division between radial and bilateral animals is second.
The difference between a radial and bilateral animal is in their symmetry. A bilateral animal, like you or me, can be divided into two indentical halves. The cnidarians, the only radial animals, have many such sections which all revolve around one point. An animal is considered bilateral or radial by the way they develop, e.g. the echinoderms, which appear as an adult to be radial, are, because they develop bilaterally, a bilateral organisms.

The next division in Kingdom Animalia is the develpment of the body cavity.
Flatworms have only one body cavity, and it does not go through their entire body. When they eat and excreat they use the same opening. Roundworms have a sudocoelem which suspends their digestive tracts in fluid. The roundworm's digestive tract goes all the way through it, so what it eats is execrated through an anus instead of being excreted through its mouth. A earthworm has a true coelem, which means that its digestive tract is held in place by tissue, instead of floating freely. All animals that are more complex than a round worm have a coelem.

The remaining animals are split into deuterostomes and protozomes.
When deuterostomes develop their cells line up in such a way that in the eight cell stage they can be divided in half with no cells being destroyed. The protostomes develop spiraly and subsequently cannot be divided like that. In a deuterostome the mouth developes from the blastopore, but a protostome developes the anus from the blastopore. The mesoderm develops from only the endoderm (the blastopore) in a deuterostome, whereas in a protostome the mesoderm developes from both the endoderm and exoderm.
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