M1: L4: Platyhelminthes

What are the characteristics of the Bilateria?

1) cephalization

2) triploblastic: 3 layers of tissues

3) complete tube-like gut

define cephalization.

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

What are the 3 major clades of bilateral animals?

1) lophotrochozoa

2) ecdysozoa

3) deuterostomia

Why is having bilateral symmetry and cephalization advantageous?

predation and movement

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)?

2) acoelomate

3) very thin, no circulatory system necessary

a) gas exchange 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 (ex: mainly trematodes (flukes) and tapeworms)

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

How does p platyhelminthes get gas into their bodies?

gas exchange occurs via diffusion

T/F - more than half of p platyhelminthes are parasitic

true

define the ganglia.

clusters of nerve cells acting similar to a brain

What is the anatomy of the tape worms?

1) scolex (looks like a head)

a) consist of the suckers and hooks — anchorages on intestinal tract

2) proglottids (ribbon-like): little reproductive sacs — mating, break off and end up in the feces

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 (parasitic fluke)?

1) female flukes are inside the male fluke

2) the mature flukes are in the human host

3) ciliated larva

4) snail host for feeding and growing

5) motile larva bores human skin

6) repeat

What disease does the schistosoma (flukes) cause?

schistosomiasis —- infects 200M ppl worldwide