Bivalves

Question 1

Phylum and class

Answer 1

Mollusca

Bivalvia

Question 2

Time period:

Answer 2

Cambrian to present

Question 3

Describe morphology

Answer 3

Calcareous valves m, equal size, plane of symmetry along hinge line, left or right valve depending on in one direction, sits above hinge line, where valves are joined. Hinge of Cardinal teeth and sockets, joined by ligament covering hinge plate. Some valves close completely, some gape if siphon extends

Question 4

What is the palliative line?

Answer 4

Marks the limit of attachment to the shell, palliative sinus indentation if siphon present

Question 5

How do the valves close?

Answer 5

Adductor muscles contact to keep closed, when muscles relaxes, external ligament pulls valves open. Some may have one central muscle, monomyarian

Question 6

What is the mode of life?

Answer 6

Evolved to fill many niches, can be bentgonic vagrant, sessile, free lying or attached, or can be burrowers. Can be found in high to low energy environments, fresh or brackish water.

Question 7

How to bivalves feed?

Answer 7

Feed using siphons, extend from shell, inhale the and exhale by, bring in water, filter feeders, particles removed from water by gills. Burrowing have long siphons

Question 8

How can bivalves move on the sediment?

Answer 8

Vagrant, muscular foot.

Question 9

How has mytilus adapted to its environment?

Answer 9

Byssus present, shell covered in periostracum

Sting shell, streamlined and unornamented, large adductor muscles to keep closed in high energy

Question 10

How are Ostrea type bivalves adapted?

Answer 10

Type of oyster, cement secreted to attach to dw floor, sting thick shell and adductor muscles, inequivalve, to form lid, one shell irregular growth with seabed.

Question 11

How are graphaea type bivalves adapted?

Answer 11

Extinct oyster, large and convex left valve for resting area so does t sink, small right valve forms lid, sting thick shell, curved to keep above sediment

Question 12

How are cytherea type bivalves adapted?

Answer 12

Shallow burrowers
Ribs and growth lined to grip sediment, small Palouse sinus and no gape so can close, unornamented streamlined shells so can move through sediment, large adductor muscles, can completely close valves for protection

Question 13

How are solen type bivalves adapted?

Answer 13

Deep burrowers, large pallial sinus indicates long siphon, unornamented and streamlined, small adductor muscles, anterior and posterior gape

Question 14

How are pecten bivalves adapted?

Answer 14

Ribbed, thin valves so sting but light, one valve curbed the other flattened to give hydrofoil effect, wars extend hinge line to direct currents, monomyarian adductor muscles to open close valves, tiny eyes on edge of mantle