Lab #7: Introduction to the Kingdom Animalia Objectives: 1 ...

Task 2: Differences between acoelomate and coelomate organisms
A major developmental event in bilaterally symmetrical organisms (see below) was the
development of a fluid filled cavity between the outer body wall and the gut (coelom). The
coelom created a tube-within-tube arrangement allowing space for visceral organs and an
increase in overall body size (Why). The coelom also provides support and aids in movement
and burrowing in some animals. However, not all organisms are coelomates, some lack a coelom
altogether and are called acoelomate (a = without) while others have a pseudocoelom (pseudo =
false). Read page 413 (exercise 38) to learn more about these organisms.
Examine the animals listed in the table below and fill out the missing sections.
Sample Organism Acoelomate Pseudocoelomate
Coelomate
(p. 402)
(p. 409)
(p. 421)
Phylum Platyhelminthes Nematoda Annelida
Genus Dugesia Ascaris Lumbricus
Common name Flatworms, planaria Roundworms Segmented worms,
Earthworms
Drawing of
Cross section
(slide)
If specimens are
available, dissect
them
longitudinally.
Draw what you see.