23. What is a trochophore larva and who has them? Platy helminthes 24. Know how

Question

23. What is a trochophore larva and who has them? Platy helminthes 24. Know how to classify flatworms according to the 4 animal body plan features (see #8). 25. Be able to explain how marine flatworms capture food ingest the food, and digest the food. What features of their body plan that allow them to do this efficiently? 26. Do flatworms have a complete gut (one with a mouth at one end and an anus at the other end)? Do they have a circulatory system? A nervous system? Excretory system? 27. Do flatworms have a skeleton? How do they move? Are they segmented 28. How do marine flatworms reproduce? 29. Know the different classes of flatworms and what characters they possess. What adaptations do the parasitic flatworms have for their parasitic lifestyle? Nematoda 30. Know how to classify nematodes according to the 4 1. Generally, how do nematodes capture, ingest, and digest 32. Do nematodes have a skeleton? Can they move? How? 33. What adaptations do the parasitic nematodes have for their animal body plan features (see #8). food? Do they have a complete gut? Are they segmented? parasitic lifestyle? Annelida 4. Know how to classify annelids according to the 4 animal body plan features (seels Previous Next

Explanation / Answer

23. Trochophore larva is circular shaped surrounded by ring of cilia, in the anterior it has tuft of cilia and at posterior a telotroch (helps in free swimming). This type of larva is mostly found in most groups of molluscs and also in Archiannelids.

Platyhelminths:

24. Flatworms named so because of its flat body. This is having a bilateral symmetry and falls under the phylum Platyhelminths with no body cavity (coelom), hence called acoelomate. these are triphoblastic animals having three germ layers(ectoderm, mesoderm, endoderm).

25. Marine flatworms like planaria, basically capture their food from slow moving organisms and ingest through the pharynx into the digestive tract, where it is digested with the help of digestive enzymes and as this flatworm is having single opening body it throw out the waste from mouth itself.

26. Basically flatworms use extracellular and intracellular digestion and as it having single opening body, all the nutrients are distributed through the branches that means it is having an incomplete digestive system. Yes, flatworms do have excretory system but a primitive one meaning that the segments are not separated off and also it has a nervous system but because of neural chords of ganglia it makes the system complicated.

27. Generally flatworms won’t exist with a skeleton but they move with help of cilia to some extent and also their body is not segmented.

28. Marine flatworms can reproduce both sexually and asexually as they have both sexual and asexual organs (hermaphrodite).

29. The different classes of flatworms are a)Turbellaria, which is a free living flatworm, b)Cestoda, and c)Trematoda are parasitic flatworms where cestoda lives in intestine and trematoda lives in a host. D)Monogenea.

Nematode:

30.Nematode belongs to nemahelminths and it has got a bilateral symmetry and body cavity is pseudocoelom.

31. Nematode has two openings i.e. mouth and anus. The food ingested from the mouth followed into pharynx where digestion takes place with the help of enzymes.

32. Nematode has got a unsegmented body and they move with the help of muscle contraction because of suppression of fluids in the body cavity.

33. In order to survival of a parasitic nematode it should get adapted to surrounding environment, hence it has got a well developed thick cuticle and sucking pharynx so that it can adhere the host and capture its nutrients.     

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