Question

1. Prepare a simple table of all the taxonomic groups, their common names, their distinguishing characteristics, and all representative genera covered below:

Phylum Mollusca (Mollusks)

            Class Polyplacophora (Chitons)

                        Katherina

            Class Gastropoda (Snails, slugs, and limpets)

                        Helix (Escargot Snail)

            Class Bivalvia (Clams, mussels, oysters, and scallops)

                        Anodonta (Freshwater mussel)

            Class Cephalopoda (Squids, Octopus, and Nautilus)

                        Nautilus (Chambered Nautilus)
                        Loligo (Squid)

Phylum Annelida (Segmented Worms)

            Class Polychaeta

Aphrodite (Sea Mouse)
Nereis

            Class Clitellata

                        Subclass Oligochaeta

                                    Lumbricus (Earthworm)

                        Subclass Hirudinea (Leeches)

                                    Hirudo (Medicinal Leech)

Answer 1

Phylum Mollusca (Mollusks):

Distinguishing characteristics of its classes and their given representative genera:

1] Class Polyplacophora (Chitons) [formerly Amphineura]:

[Foot sole-like or reduced or absent; Shell formed of 8 plates or absent]

Genus Katharina tunicata:

[medium sized chiton, with length of about 12 cm; it has girdle (mantle's dorsal portion that borders the 8 shell plates) which is shiny black covering all except mid-dorsal area and it is its characteristic feature]

2] Class Gastropoda (Snails, slugs, and limpets):

[Largest class of molluscs; Part of foot modified into stomach; Shell spirally coiled, univalvular, unilocular]

Genus Helix (Escargot Snail):

[large, air-breathing land snails; terrestrial, have a simple lung for respiration; hermaphroditic; head has two pairs of tentacles- upper larger pair contain eyes, and lower pair used to feel the ground;  mouth has radula composing many chitinous teeth]

3] Class Bivalvia (Clams, mussels, oysters, and scallops):

[Foot wedge-shaped; Shell formed of two valves hinged dorsally]

Genus Anodonta (Freshwater mussel):

[composed of 12 species; Anodonta cygnea has very large elongate to oval, thin shell;  periostracum glossy brown, sometimes with shades of green or yellow-green; Umbos beyond middle, towards front end]

4] Class Cephalopoda (Squids, Octopus, and Nautilus):

[Shell may be internal (in Sepia), or external (in Nautilus), or absent (in Octopus); Foot partially modified into head with 8 or 10 arms and partly into siphon]

Genus Nautilus (Chambered Nautilus):

[Known as living fossil; Has external, coiled, chambered decorative shell; Floats by secreting a gas in the chambers]

Genus Loligo (Squid):

[Marine, good swimmer, carnivorous; Similar to Sepia, except that their fins are present only in posterior half, and meet posteriorly]

Phylum Annelida (Segmented Worms):

Distinguishing characteristics of its classes and their given representative genera:

1] Class Polychaeta:

[Locomotion- many setae on parapodia, one pair per segment; Clitellum absent; Unisexual; Development indirect with trochophore larva]

Genus Aphrodite (Sea Mouse):

[marine worms; shows bioluminescence; covered in dense mat of parapodia and setae; the spines or setae are its unique features]

Genus Nereis:

[commonly known as rag worms or calm worms; body long, slender, dorso-ventrally flattened; has closed circulatory system but no heart; reproductive phase called heteronereis; head has two parts: prostomium (roughly triangular anterior lobe) and peristomium (posterior ring-ike portion)]

2] Class Clitellata:

[Annelid worms, characterized by having clitellum (collar forming a reproductive cocoon during their life cycles; do not have parapodia; heads less developed]

Subclass Oligochaeta:

[Locomotion by a few setae per segment; Clitellum permanently present; Hermaphrodite; Development direct]

   Genus Lumbricus (Earthworm):

[Earthworm is fossorisal; shows cross fertilization due to protandrous condition; first segment is peristomeum; has female gonophore in 14th segment, and two male gonophores ion 17th and 19th segments; Larger Lumbricus terrestris worms crawl at a greater absolute speed than smaller worms]

  Subclass Hirudinea (Leeches):

[Locomotion by suckers; Clitellum developed in breeding season only; Hermaphrodite; Development direct]

   Genus Hirudo medicinalis (Medicinal Leech):

[Amphibious, fresh water leech; they moves in water by contracting longitudinal muscles in wave-like motion, moves on land by looping; has cylindrical, dorsoventrally flattened body divided into 33-34 segments; has three jaws which works back and forth during feeding and leaves a tripartite star-shaped scar on host]