M10/11 introduction to vertebrates

Question 1

Molluscs

Answer 1

30.56% of the Kingdom animalia (130,000 species of mollusc). 500mya they were very diverse, adapt to many aquatic and terrestrial environments.

Many have a mantle which secretes a shell, many crawl with muscular foot. They can have a head with tentacles and feeding via radula, visceral mass contains internal organs. Circulation (haemolymph is their blood with respiratory pigments, some have haemoglobin too, sometimes hemocyanin (with copper)), have hearts, gills.

Question 2

Superclass Aplacophora

Answer 2

Shell-less. Classes = Solenogastres, Caudofoveata. 300 species.

Small class of marine, shell-less worm-molluscs. Reduced narrow foot, lacks intrinsic musculature, mantle covered by chitinous cuticle and calcareous sclerites (not plates). Radula, mostly detrivores.

Question 3

Class Polyplacophora

Answer 3

Chitons (‘bearing many plates’)

Shell has 8 overlapping plates/valves with a ‘girdle’ of scales/spicules. Brad foot in mantle with gills, simple head/no tentacles. Grow to 30cm in size, feed with radula (herbivores, detrivores).

Question 4

Class Monoplacophora

Answer 4

Bearing one shell (not a limpet, a limpet is a gastropod). 30 species,

Have a single true shell. Foot, mantle with gills, feeds in a similar way to chitons. Known as living fossil, one of the most primitive mollusc species.

Question 5

Class Scaphoda

Answer 5

‘tusk shell’
Vary in size (mm - cm), diameter of around 1cm. Shell is tubular, cylindrical-conical, more or less curved, open at both ends. Feeds on foraminifera using captacula (feeding tentacles). Reduced foot, no eyes or gills, gaseous exchange from mantle.

Question 6

Class Cephalopods

Answer 6

Over 800 species, mm - 14m (giant octopus).

Encompass the squid, octopus, cuttlefish and nautili. Prominent head, tentacles and modified from molluscan foot, radula (beak), most cognitively advanced group of invertebrates.

Question 7

Class Nautiloids

Answer 7

External shell. Coleoid (squid octopus), shell is internal, reduced or lost, muscular mantle sucks up water to pass over gills. Arms for prey handling, closed circulatory system, jet propulsion for locomotion in squids (water is drawn in through openings in head, also ventilates gills. Openings shut and water is pumped out though the body. Muscular mantle which draws water in which also ventilates gills. Head fins and tentacles are splayed like wings.

Question 8

Jet propulsion (squids)

Answer 8

Generation of lift force and control of different body postures in different flight phases. Enhances escape from predators. 4 phases in flight process: launching, jetting, gliding, diving.

Question 9

Class Gastropoda

Answer 9

One of most diverse clades (snails, limpets, nudibranchs).

Marine, freshwater and terrestrial. Mainly shell-bearing, distinct and moveable head with eyes. Distinct, separated foot. Helix-like visceral hump (snail like). Visceral mass with organs. Torsion = can twist head, foot and internal organs 180 deg during development (end up with their anus on their head). Radula (tongue-like thing with teeth on it) is ribbon-like with teeth that slide over cartilaginous odontophore (when not feeding, housed in radula sac). When feeding, muscles push odontophore and radula out to get food, then retracts and pass to oesophagus.

Question 10

Class Bivalvia

Answer 10

10,000 extant species

One of most diverse molluscan classes. Important for food/trade (oysters, pearls, medicine). Laterally compressed bodies enclosed by a shell with two hinged parts, bilateral symmetry. No head or radula (filter feed, siphons water that is passed over gills for respiration and feeding. Ciliary motion of gills passes food to mouth). Paired shells (open and close during muscle sets). Don’t take on all particles, tend to choose by size.