M1: L5: Platyhelminthes

What are the characteristics of the Bilateria?

1) have bilateral symmetry

2) cephalization

3) triploblastic: 3 layers of tissues

define cephalization.

organization of nerves and sensory organs at one end (the head)

Why is having bilateral symmetry and cephalization advantageous?

???

What are the 3 major clades of bilateral animals?

1) lophotrochozoa

2) ecdysozoa

3) deuterostomia

What phylums are in the lophotrochozoa?

platyhelminthes, mollusca, annelida

What phylums are in the ecdysozoa?

nematoda, arthropoda

What phylums are in the deuterostomia?

echinodermata, chordata

What are the characteristics of the phylum platyhelminthes?

Flatworms:

1) triploblastics

2) no body cavity (acoelomate)

3) very thin, no circulartory system necessary

a) gas exchange occurs via diffusion

4) simple gastrovascular cavity with a single opening (incomplete gut)

5) free living (salt and fresh water as well as damp terrestrial) and parasitic species

a) more than half are parasitic — mainly trematodes (flukes) and tapeworms

incomplete gut means the mouth/anus so what goes in and what goes out are at the same area

What are the body parts of the planaria?

ganglia: clusters of nerve cells acting similar to a brain

ventral nerve cords

gastrovascular cavity

pharynx: secretes digestive juices on the food

mouth

eye spots

What are the life cycle of the tape worms?

skull ex consist of the suckers and hooks — anchorages on intestial tract

scolex: ribbon-like

proglottids: little reproductive sacs — break off and end up in the feces

can self-fertilize

How do tape worms end up back into the host?

1) proglottids fold back — self-fertilize

2) break off and end up in the feces

3) rely on an intermediary host: adult flea or larval flea

4) the flea bites on the host

5) the host digest the flea containing the tapeworm inside

What is the life cycle of the schistosoma (parasistic fluke)?

1) female flukes are inside the male

2) the mature flukes are in the human host

3) ciliated larva

4) snail host

5) motile larva

What disease does the schistosoma cause?

schistosomiasis