Intro to Platyhelminthes

Question 1

What are defining characteristics of phylum Platyhelminthes?

Answer 1

NONE
- there are no unique, defining features that separate these creatures from other phylums

Question 2

What are some unifying features of phylum platyhelminthes?

Answer 2

• bilaterally symmetric
• moderate degree of cephalization
• forage for food
• triploblastic
• acoelomate

Question 3

Instead of actual hydrostatic skeletons, Platyhelminthes have…..

Answer 3

parenchyma tissue they use to act as hydrostatic skeletons for them

Question 4

What is parenchyma tissue?

Answer 4

• loose aggregation of fluid filled cells, developed from mesoderm, that Platyhelminthes use as a hydrostatic skeleton
• allows for fluids, nutrients, gases and waste to circulate through the body

Question 5

what does an incomplete digestive system, with one opening to the gut mean for organisms?

Answer 5

they need to pass out waste products before they can consume more

Question 6

Sexually, Platyhelminthes are _____ ____________

Answer 6

simultaneous hermaphrodites

Question 7

Describe the anatomy (brain, digestive system, excretory system) of platyhelminthes

Answer 7

Brain: central nervous system is present but very simple

Digestive system: incomplete digestive system, single opening to gut

Excretory: works via ultra-filtration, only allows small molecules to pass through the filter and be excreted.

Question 8

Platyhelminthes/flat worms are thought to be the _____ group to all other bilaterian animals

Answer 8

BASAL

Question 9

what percent of flatworms are parasitic? what group is this called?

Answer 9

80% are parasitic, and they are all called Neodermata

Question 10

What classes are apart of the Neodermata/parasitic group of flatworms?

Answer 10

• Trematoda
• Cestoda
• Monogonea

Question 11

What class of flat worms are NOT parasitic (for the most part)?

Answer 11

Class Turbellaria

Question 12

Class turbellaria is mostly ____ living, but there are some_____ species that developed from convergent evolution, independently from neodermata

Answer 12

Class turbellaria is mostly free living, but there are some parasitic that developed it from convergent evolution, independently from neodermata

Question 13

How to Turbellaria reproduce?

Answer 13

• reciprocal sperm transfer, using hypodermic insemination where they stab their partner directly into the body wall and inject sperm

Question 14

Most turbellaria living in _____ environments

Answer 14

terrestrial

Question 15

What kinds of musculature do turbellaria have?

Answer 15

• circular (constrict)
• longitudinal (shorten)
• dorsoventral (bend)

Question 16

How do turbellaria move?

Answer 16

• through duo-glands.
• one end of the flat worm sticks, contract, posterior attaches, then body lengthens
• they can also swim

Question 17

Turbellaria feed using ….

Answer 17

a protrusive pharynx

Question 18

What are major conditions/steps for parasites?

Answer 18

1. Reproduce within the definitive host
2. Get offspring out of the host
3. Contact a new, appropriate host
4. Gain entry into the host
5. Navigate to an appropriate tissue/organ
6. Maintain position within the host
   a. Hosts are always trying to reject. Hosts benefit by eliminating parasites
   b. So this is a battle. Evolutionary arms race. Holding on is important for the parasite.
   c. Adaptations of parasite for maintaining position are usually visible to our eye.
   d. Rest of the body is usually “simplified” by natural selection.
7. Withstand anaerobic conditions
   a. Not a problem with ectoparasites. Only an issue deep inside tissue
8. Avoid digestion or immune attack
   a. Many parasites have an immune suppressant so the immune system of the host doesn’t attack them.
9. Keep from killing the host before 1
   Balance.
   a.Negative effects cannot be so negative it kills the host