Introduction
This tutorial continues our discussion of the major features of animal
evolution, concentrating on the bilateria. Previously we introduced three
phyla: Porifera, Cnidaria, and Platyhelminthes. These groups include
representatives of the parazoa, radiata, and bilateria, respectively. We will
begin by distinguishing among the organisms with body cavities, the
pseudocoelomates and true coelomates. We will then discuss representative
lineages of the protostome coelomates, including mollusks, annelids and
arthropods. As you progress through this tutorial, compare and contrast
these protostome taxa. How are these groups of animals similar? What
morphological and developmental patterns do they have in common? How do they
differ?
By the end of this tutorial you should have a basic working understanding
of:
- How specific organisms coincide with the major branch points in the
phylogenetic tree in the evolution of animals
- Characteristics of
organisms in Phyla Nematoda
- How some species of roundworms
cause disease in humans
- The members of the Phylum Mollusca, and
the constraints a shell imposes on their body plan and development
- The
importance of segmentation in the annelids
- Why the animals in
Phylum
Arthropoda are thought to be so successful
- The diversity of
ecologies and body plans in the Phylum Arthropoda
- Identify the two groups of pseudocoelomates, their general
characteristics and the human impacts of nematodes
- Compare and
contrast the two groups of animals with true coelems, the protostomes
and
deuterostomes, including the differences in development seen in these
two
groups
- Discuss the characteristics of the organisms that are
members
of the Mollusca
- Describe the characteristics of the organisms
that
are members of the Annelida
- Explain the characteristics of
arthropods that have made them successful
- Describe the diversity
of
arthropod groups, including trends in arthropod evolution