Unit III: Protostomes

Question 1

What are the two Protostomes - Ecdysozoa?

Answer 1

• Nematoda
• Arthropoda

Question 2

List Nematoda characteristics

Answer 2

• Round, unsegmented worms (roundworms)
• Outer cuticle is rich in collogen and chitin
• Molt during growth
• Widespread and can be abundant
• Free-living and parasitic species

Question 3

List Arthropoda characteristics

Answer 3

• Grow by molting an outer exoskeleton (made of chitin, provides protection, and structure for muscle attachment)
• Body is segmented into discrete regions
• Movement due to jointed appendages
• Homocoeal (central body cavity) with open circulatory system in which no distinction between blood and interstitial fluid
• Gas exchange occurs spiracles (pores) in exoskeleton, while aquatic crustaceans use gills

Question 4

Arthropoda - Chelicerate

Answer 4

• horseshoe crabs, spiders, mites, ticks, and scorpions
• Chelicerae: a pair of appendages in front of the mouth
• Loss of antennae, usually two magmata with no discernible head
• Pedipalps: the second pair of appendages attached to the cephalothorax

Question 5

Chelicerae

Answer 5

modified first pair of appendages often form specialized claw-like or fang-like mouthparts

Question 6

Pedipalps

Answer 6

second pair of appendages that often have roles in sensing environment or manipulating food

Question 7

Arthropoda – Crustacea

Answer 7

• Most dominant aquatic arthropods; includes shrimp, lobsters, krill, crabs, and crayfish
  – But also terrestrial groups like isopods (“pill bugs”)
• Typically have…
  – Head and thorax fused into a cephalothorax
  – Two antennae
  – Biramous (two-branched) appendages

Question 8

Arthropoda – Hexopoda

Answer 8

• Insects; Largest group of arthropods
• Typically have…
  – Six legs
  – Three tagmata (head, thorax, abdomen)
  – Wings (secondarily lost in some groups)

Question 9

What are the defining traits of Arthropods?

Answer 9

• Chiton exoskelton
• Jointed appendages
• Tagmata
• Hemocoel with open circulatory system

Question 10

What are the 2 Protostomes - Lophotrochozoa?

Answer 10

1. Mollusca
2. Annelida

Question 11

What is Mollusk body plan ?

Answer 11

3 major parts:
- Foot: large muscles at base of individual, usually used for movement
- Visceral mass: region containing most of the internal organs as well as external gill
- Mantle: specialized epidermis that encloses all visceral organs and secretes shells

And Radula

Question 12

Radula

Answer 12

tongue-like organ with chitinous ornamentation

Question 13

How do Snails, Bivalves, Cephalopods move?

Answer 13

Snails - waves of muscle contraction along foot allows individuals to “crawl”
Bivalves - digging appendage
Cephalopods - forms tentacles for crawling and grasping

Question 14

Bivalvia characteristics

Answer 14

• Bivalvia = “two-valves”
• Clams, oysters, mussels, scallops
• Modified foot for digging
• Poorly developed head area with no defined mouth
• Loss of radula

Question 15

Gastropoda characteristics

Answer 15

• Gastropoda = “stomach-foot”
• Snails, slugs, conches
• During development undergoes torsion: rotation of the mantle and visceral mass 180
• Creates space in visceral mass that allows withdrawal of head

Question 16

Cephalopoda body plan

Answer 16

Octopuses, squid, cuttlefish, and nautiluses
- Foot typically modified to tentacles
- Many display and rapidly change an array of colors
- Chromatophores

Question 17

Chromatophores

Answer 17

specialized pigment cells in that expand and contract to produce different color patterns

Question 18

Annelida characteristics

Answer 18

Segmented worms, earthworms, leeches, polychaete
- Metamerism: series of body structures that are similar internally and externally, such as segments
- During development, the segments behind the head arise sequentially from a growth region anterior to the tail, a pattern called teloblastic growth
- Two opening in digestive tract and closed circulatory system
- Setae
- Clitellum
- Filter feeders
- Some live around deep sea hydrothermal vents
- Secrete mineral “tube” around body

Question 19

Setae

Answer 19

chitinous hairs that are attached to muscle, extend through epidermis, and provide traction

Question 20

Clitellum

Answer 20

specialized band of fused segments, which aids in reproduction

Question 21

What are the defining traits of Lopotrochozoa?

Answer 21

Mollusks:
- Body plan: foot, visceral mass, mantle
- Radula

Annelida:
- Metamerism with teloblastic growth
- Setae
- Citellum