Topic 23 Ecdysozoa

Question 1

Clade bilateria includes

Answer 1

lophotrochozoa, ectodyzoa, and deuterostomia

Question 2

Ecdycozoans are the most __ rich animal group

Answer 2

species

Question 3

Two alrgest ecdycozoan phyla

Answer 3

nematodes and anthropods

Question 4

epidermis

Answer 4

tough, non-living, outer layer of organic material deposited outside of the epidermis. The cells of the epidermis secrete the cuticle

Question 5

cuticle functions

Answer 5

barrier against desiccation and prevents mechanical injury, forms a tough-external skeleton that gives ecdysozoan bodies shape, provides rigid frame for muscle attachment

Question 6

Ecdysozoans shed their cuticle to ____

Answer 6

grow because the cuticle is non-living

Question 7

Three layers of the cuticle

Answer 7

• Endocuticle (endo = within)
  − Exocuticle (exo = outside)
  − Epicuticle (epi = upon): thin, waxy

Question 8

Fine ducts run from the epidermis to ____

Answer 8

Fine ducts run from the epidermis to the top of the cuticle

Question 9

ecdysis of the cuticle allows:

Answer 9

ecdysozoans to increase their body size in a step-wise manner

Question 10

sclerotized cuticle means

Answer 10

that it is hard because of the cross-linked chitin polymers (but only specific regions are hardened and some are soft so they can still move)

Question 11

process of molting

Answer 11

1. Old cuticle separates from the underlying epidermis.
2. Inactive enzymatic molting fluid is secreted into the separation space, and growth of the epidermis (cell proliferation and enlargement) increases its surface area (folds)
3. A new proto-epicuticle, a thin protective layer, is deposited on the surface of the epidermis
4. Molting fluid enzymes are activated
5. a - Old endocuticle digested
6. b - Sclerotized exocuticle is not digested
7. c - − A new undifferentiated procuticle layer is deposited beneath the proto-epicuticle, which protects the newly deposited procuticle from being digested
8. Molting fluid reabsorbed
9. deposition of new epicuticle is completed
10. old exocuticle is molted via ecdysis
11. the outer layer of the new protocuticle is sclerotized by secretions via cuticle ducts to form exocuticle above the unsclerotized endocuticle

Question 12

Phylum Nematoda

Answer 12

Nematodes: roundworms or threadworms that are found in most aquatic habitats, soil, plant tissue, and body fluids

Question 13

Nemetodes have a morphologically ___ body plan

Answer 13

simple with a complete digestive track but lack a circulatory system

Question 14

hemocoel.

Answer 14

Body cavity not completely lined by mesodermally-derived tissues. Nematodes have a hemocoel