Exam 5 Material (Mullusca: Group of Lophotrochozoa)

Question 1

Is mollusca the biggest group of lophotrochozoas?

Answer 1

Yes

Question 2

What are all molluscas?

Answer 2

Coelomates (have a coelom)

Question 3

How many basic characters do mollusks have?

Answer 3

6 basic characters (dorsal shell: made up of calcium carbonate, a muscular foot: located ventrally/belly side of their body, ventral mass: contains organs sitting just above/dorsal to the foot, mantle: has glands that secrete at the shell, mantle cavity: usually contains the gills/lungs, regula: Found in most molluscs, but not in filter-feeding ones/is a mouthpart)

Question 4

What is special about mollusks coelom?

Answer 4

It is reduced to nothing but a series of small compartments that are around the organs (causes coelom to not be very large)

Question 5

What kind of circulatory system do mollusks have?

Answer 5

Open circulatory system (does not have a complete set of vessels circulating their hemolin throughout the entire body—rather the hemolin bathes the cells of most of the body directly/surrounds all of the different tissues but there are some vessels but these small vessels then empty into the hemoseal, which is the main body cavity this is where CO2 and waste products are given off by the cells and they pick up oxygen—gills are where gas exchange happens)

Question 6

What kind of movement/oxygen exchange do molluscs have?

Answer 6

Most mollusks are slow moving/do not need efficient oxygen exchange

Question 7

What is being described (type of mollusk):
They have many plates (have eight plates—located dorsally)—their foot acts as a suction cup and holds them fast to rocks (so when they’re hit w/ heavy waves, they’re not wasted off)—they use their regula (a hard structure) to scrap food off the surface of rocks

Answer 7

Polyplacophore (chitins)

Question 8

What is being described (type of mollusk)?:
Literally means “stomach foots” (they walk around on their foot, which is on the ventral side/stomach)—includes both snails and slugs—vast majority of mollusks—most are marine/some live in freshwater/some live on land—have well-developed head and tentacles—have tortion (a twisting of their ventral mass—created “U” shape—the anus turns around and comes anteriorly again)—have a mouth going through their esophagus/digestive tract and their anus comes back out towards their head)

Answer 8

Gastropods

Question 9

What is being described (type of mollusk):
Are fast predators—they have well-developed eyes (are structurally similar to a vertebrate’s eyes, however, they’re more closely related to a clam)—have ability to change color (structures in their skin called chromatophores—will release different types of pigments)—produce an ink-like substance that they can squirt out using their cyphon (comes from their mantle)/can also squirt out water)

Answer 9

Cephalopoda (octopods, squids, nautili)

Question 10

What is special about octopods (type of cephalopoda)?

Answer 10

They have no shell (can squeeze through small areas)

Question 11

What is special about squids and cuttlefish (types of cephalopods)?

Answer 11

They have an internal shell

Question 12

What is special about the nautili (type of cephalopod)?

Answer 12

They are the only extant group of cephalopods that have an external shell (shell is built w/ chambers that have trapped gas in them that provides buoyancy/the ability to float)

Question 13

What type of nervous system do all cephalopods have?

Answer 13

A closed nervous system (instead of opening up into the hemolin/hemocoel, they have vessels that travel around to different parts of the body carrying the hemolin for gas and waste exchange)