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Student Resources
Nematoda -Workbook QuestionsIn this new taxonomic scheme, make a list of
the phyla that would be included in the Ecdysozoa. (p. 44)
The Ecdysozoa includes the following
phyla: Arthropoda, Onychophora, Tardigrada, Nematoda, Nematomorpha,
Loricifera, Kinorhyncha, and Priapulida.
How do
pseudocoelomates swallow their food?
(p. 44)
A pseudocoelomate’s body cavity is not
completely lined by mesoderm, and the endoderm of the gut has no
mesodermal musculature. During embryological development, the gut forms as
a pair of invaginations at each end of the embryo. They connect with
endoderm in the middle to create the hollow tube, an archenteron, that
runs through the embryo. As a result, the most anterior and posterior
parts of the digestive tract are ectodermal in origin with only the middle
region formed from endoderm. In pseudocoelomates, mesoderm is only found
next to ectoderm, and that’s why the most anterior and posterior parts of
the digestive tract have muscles. At the anterior end are two rings of
musculature on either side of the pharynx. To swallow their food, the
posterior ring of muscles contract to close the gut, the anterior muscle
ring relaxes, the pharynx expands, and food is pulled in. Next, the
anterior ring of muscles close, the posterior relax, and the pharynx
contracts pushing food into the
intestine.
There is another advantage
to having a tube-within-a-tube construction that other animals with a
complete digestive tract have that nematodes don’t have. What is it? (p. 46)
One of the advantages of this type of
construction is that the gut can move independently of the body wall. An
animal can appear to be sessile while peristaltic movements of the gut
musculature assist with digestion of ingested food. Pseudocoelomates don’t
have mesoderm adjacent to their endoderm, and musculature doesn’t line
most of their gut. In these animals, body movements are still important
for propelling food through the alimentary.
Is there any
other way that you could tell the difference between the sexes? (p. 46)
It’s easy to see the difference between the sexes in the cross section slides. Because the reproductive ducts of the female are paired, you can see duplicates of each structure--paired oviducts, uterus, and ovaries. In the male there is no such duplication of the reproductive structures.
Protozoa || Porifera ||
Cnidaria ||
Platyhelminthes || Nematoda || Annelida ||
Mollusca || Arthropoda
Echinodermata || Chordate Origins ||
Jawed Fishes || Amphibia ||
Mammalia
