Cephalopods

Question 1

Cephalopod lifestyle

Answer 1

Most sophisticated
Carnivores - geared up for predation
Active life style
Jet propulsion through squirting water through the exhaling siphon to move very quickly
Complicated courtship - dioecious

Question 2

Cephalopod morphology

Answer 2

Mantle cavity relies on muscular contraction (not cilia)
Water pumps in and out through siphons
Shell reduced or lost (except Nautilus)
Vulnerable cos of this so have
-inc sacs (cloud to stop predator from seeing)
-chromatophores in skin to change colour (used for crypts and reproduction)
Radula/jaw/beak to subdue prey

Question 3

Cephalopod sensory features

Answer 3

Well developed NS and brain (memory etc. octopi can learn from observation)
Eyes well developed - like vertebrate (convergent E)
-operates slightly differently, moves lens position to focus
Evolutionary adaptation of not picking up sound - used to catch prey using sound, now predators use as lure

Question 4

Transport system of molluscs

Answer 4

Only molluscs to have closed circulatory system
Have 2 accessory hearts as well as main
1. Accessories pump blood to gills
2. Oxygenated blood from gills to main heart and rest of body
Have high metabolic rate so allows efficient circulation and oxygenation for tissues

Question 5

Natuiloids

Answer 5

Appeared in Cambrian
Lives in end of chambered shell
Funnel which leads to mantel cavity, used for movement and pushing water
Chambers in shell can be used as buoyancy aid
Siphuncle runs through the shell can concentrate solutes in certain chambers - water moves by osmosis, and leaves air spaces in others, changing buoyancy (and vice versa)
Nautilus eye simple - no lens

Question 6

Coleoiudea

Answer 6

Cuttlefish - internal shell, cuttlebone used as buoyancy like nautilus
Squids - shell reduced to proteinaceous pen
-used for support, stops body distortion when muscles contract & keeps longitudinal shape
Octopuses - shell vestigial or absent
-different mode of action, crawl and go in small spaces, need this for flexibility (wouldn’t have this if had shell)

Question 7

Different types of shells in cephalopods

Answer 7

Ancestral form like straight-shelled nautili (not curved)
From ancestral condition, squids have retained straight pen-like structure
Cuttlefish have retained the middle bit (chambered bit)
Octopus has lost all of it