Question

With reference to flatworms answer the following parts :

a.What are the best known representatives of the Platyhelminth phylum?

b. What is the main external morphological feature that differentiates platyhelminthes from other worms (nematodes)?

c.How many germ layers make up the body of platyhelminthes? How are they classified according to this feature?

d.What are the types of digestion and digestive system of platyhelminthes?

e.How are nutrients distributed by the digestive system in planaria?

f. How is gas exchange carried out in flatworms?

g.Poriferans and cnidarians do not have excretory systems. Do platyhelminthes have an excretory system?

h.What is an example of a freshwater flatworm? What physiological problem must these animals solve when living in that environment?

i.Is the nervous system of platyhelminthes more or less sophisticated than that of cnidarians1? What are the main neural structures found in flatworms? How is this neural organization important for the diversity of ecological niches explored by species of the phylum?

j.What is cephalization? How does lateral symmetry favor cephalization?

k.Do platyhelminthes use sexual or asexual reproduction?

l.How can asexual reproduction in planaria be described?

m.Are flatworms monoecious or dioecious?

n.Is it possible for a hermaphrodite species to carry out cross-fertilization?

o.What is direct development? Do planaria have a larval stage?

p.Into which classes are platyhelminthes divided? How can these classes be described and what are some representative species in each of them?

q.What are the main human diseases caused by platyhelminthes?