Exercise 8: Survey of Animal Diversity
Sponges, Cnidarians, Flatworms, and Roundworms
Week of March 17, 2008
List the distinguishing characteristics of the Kingdom Animalia.
Describe the types of features that determine an animal’s “body plan” (e.g., type of symmetry; diploblastic
triploblastic; types of body cavity; incomplete gut
complete gut; type of skeleton, etc).
Identify members of the four phyla covered in today’s lab: Porifera, Cnidaria, Platyhelminthes, and Nematoda.
Identify members of the three major classes of the Platyhelminthes: the Turbellaria, Trematoda, and Cestoda.
Describe the distinguishing characteristics of each phylum and how those features relate to the biology of
phylum members. List the types of habitats inhabited by members of each phylum (marine, freshwater,
terrestrial, or parasitic).
Most of us identify animals as motile, non-photosynthetic creatures. Indeed, most animals do have some mode
of locomotion and all are
, mostly with
(eat other organisms or their parts and
digest them internally). Animals have
, and, like many algae, most fungi and all plants, they are
. Individual animal cells lack a rigid, layered cell wall, but the body is typically supported internally
by a unique kind of
rich in hydrated carbohydrates and structural proteins, including
is a glycoprotein (a protein with a covalently attached carbohydrate) that
is unique to animals.
Most of it is
arranged into minute, stretch-resistant fibers, that form a three-dimensional scaffolding upon which the various cells
of the body are arranged.
In humans, collagen composes up to 50% of total protein. Also unique to animals (but not
necessarily present in all cells or tissues) are specific kinds of
. These are complexes of structural
proteins that join adjacent cells and allow the cells to function as a coordinated tissue (see Fig. 6.31 in your text).
Animals probably evolved from colonial protozoan ancestors, which exhibited some division of labor amongst
cells (e.g., somatic cells
reproductive cells). Animals carry the division of labor to new extremes. For example,
humans contain 200 different cell types. Similar types of cells are typically grouped together to form functional
and different types of tissues are arranged into larger functional units, the
Animals have a
life cycle – the unicellular gametes are the only haploid stage. Typically,
animals are oogamous, producing a large non-motile egg (or
eggs) and small, swimming sperm. Following fertilization, the
to form a spherical
. In the
simplest animals, the sponges, this blastula develops directly
into a swimming
which metamorphoses into an
adult sponge. In all other animals, one side of the blastula
invaginates to form a
and the embryo begins to