Objective 1. Describe how the prominent characteristics of platyhelminths and ne
ID: 9488 • Letter: O
Question
Objective 1.Describe how the prominent characteristics of platyhelminths and nematodes promote their survival and reproduction.
Objective 4.
List the characteristics of flatworms and roundworms more advanced than those of more primitive phyla.
Objective 6.
Understand the difference between acoelomate, pseudoceolomate, and coelomate and know which phyla are associated with each.
j. Consider objective 1 listed at the beginning of this exercise. How could being monoecious contribute to the evolutionary success of flatworms in their environment?
k. Planarians have a head. In biological terms, what constitutes a “head”? How does it relate to objectives 1, 4, and 6?
The cuticle of Ascaris is flaky and tough. Consider objective 1 listed at the beginning of this exercise. What might be an adaptive advantage of a thick and tough cuticle?
Explanation / Answer
Obj 1
Platyhelminths (flatworms)
- bilateral symmetric
- flat body
- unsegmented acoelomates
- gastrovascular cavity but no digestive cavity
Namatodes(roundwormes)
- cylindrical
-unsegmented pseudocolemates
- tapered ends
- no circulatory systems
Obj 4
Acoelamates(w/o a body cavity) like Plathyhelminthes and Pseudocolemates like Namatodes have true tissue, bilaterly symmetrical, and are protostomes unlike other primitive phylas.
Obj 6
acoelomate
-associated with the phyla Platyhelminthes
- lack a body cavity between the digestive cavity and outer body wall
pseudoceolomate
-associated with the phyla Nematoda
- have a body cavity lined in part by tissue derived form mesoderm and tisues derived form endoderm
coelomate
- true coelom
- associated with the phyla Mollusca
- body cavity completely lined by tissue derived form the mesoderm
j.monoecious meaning that the flatworm contains both male and female sex organs that contriute to an increase in reproductive success
k.Planarian is the common name given to many non-parasitic flatworm, has a simple brain (ganglia) and nervous system, plus 2 eyespots
Pseudocoelomates have cuticles to protect he internal structure of the worm
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