mighty Mighty Molluscs!

Body of Mollusc

Molluscs The life cycle of many marine mollusks includes a ciliated larvae, the _______________________. This larva is also found in marine _______________ (segmented worms) A trochophore larva.

Class of Polyplacophora - chitons Marine; oval shapes and shells divided into eight dorsal plates. Muscular _______ grips the rocky substrate tightly and creep. Grazers; use _____________ to scrape and ingest algae.

Class of ___________________ More than ________ species; mostly _______, but also many freshwater species. ________________ Garden snails and slugs have adapted to land. In place of the gills found in most aquatic gastropods, the lining of the mantle cavity of terrestrial snails functions as a lung

Shell-less nudibranchs Class of Gastropoda Most gastropods are protected by ____________________________ into which the animals can retreat if threatened. Other species have lost their shells entirely and may have ___________ defenses against predators (They can handle the nematocysts from anemones). Shell-less nudibranchs (____________)

Class of Gastropoda Many gastropods have distinct heads with __________ at the tips of tentacles. Queen Conch

Class ___________________ ____________ shells connected with a ______. Clams, oysters, mussels, and scallops. Bivalves have shells divided into two halves. The two parts are hinged at the mid-dorsal line, and powerful _______ muscles close the shell tightly to protect the animal. When the shell is open, the bivalve may extend its hatchet-shaped ____ for digging or anchoring.

Class Bivalvia The ______ cavity of a bivalve contains gills that are used for feeding and gas exchange. Most bivalves are _______ feeders, trapping fine particles in mucus that coats the gills. ________ convey the particles to the mouth. Water flows into mantle cavity via the _______, and passes over the gills, and exits via the _________ siphon.

Class of ________________ _______-Footed Molluscs Use ____ movements to dart toward their prey which they capture with several long _________. Squids and octopuses use beaklike ____ to bite their prey and then inject poison to immobilize the victim. A mantle covers the _________; shell is _______ and internal in squids, missing in many ______. Only ________-______ ___ has external shell.

Cephalopods Fast movements by a squid occur when it contracts its mantle cavity and fires a stream of ______ through the ___________ siphon. By ________the siphon in different directions, the squid can rapidly move in different directions. The ______ of a cephalopod (“head foot”) has been modified into the muscular siphon and parts of the tentacles and head.

Nautilus This is the ________ nautilus, a type of Cephalopod, with up to 90 short __________tentacles used to capture prey A series of ____-filled chambers serve as a ___________ device

Cephalopods Unique among mollusks, cephalopods have a ____________ circulatory system to facilitate the movements of gases, fuels, and wastes through the body. They have a well-developed __________ system with a complex _______ and well-developed __________ organs. This supports learning and ___________ behavior.

Highly developed _____ and ____ in cephalopods

Traditional __________ tree of animals - based mainly on grades in body “plans”, and characteristics of __________ development Each major branch represents a ______, defined by certain body-plan features shared by the animals belonging to that branch. unresolved

The first branch point ( ) splits: The major grades are distinguished by structural changes at four deep branches. The first branch point ( ) splits: the ________ - lack true tissues, from the the ____metazoa - have true tissues. The Porifera or sponges, represent an early branch of the animal kingdom. Sponges have unique development and a structural simplicity. 1

(2) Second branch point -- The eumetazoans are divided into two major branches, partly based on body symmetry. Radiata - _______ symmetry. Cnidaria (hydras, jellies, sea anemones etc), Ctenophora (comb jellies). -- Bilateria – ____lateral symmetry with a dorsal - ventral side, an anterior and posterior end, and a left and right side. 2 Linked with bilateral symmetry is cephalization, an evolutionary trend  anterior CNS, extending to the tail end as a longitudinal nerve chord.

(3) Third branch point -- Bilateria divided by the presence or absence of a ______________ (a fluid-filled space separating the digestive tract from the outer body wall) and by the structure the body cavity. i. Acoelomates (the phylum Platyhelminthes) have a solid body and ___________ a body cavity. 3

ii. ________coelomate - there is a body cavity, but it is not completely lined by mesoderm. Pseudocoelomates include the rotifers (phylum Rotifera) and the roundworms (phylum Nematoda).

iii. ____________ -- true coelom, a fluid-filled body cavity completely lined by mesoderm. The inner and outer layers of tissue that surround the cavity connect dorsally and ventrally to form mesenteries, which suspend the internal organs. Include phylum mollusca and up…..

(4) Fourth branch point -- Coelomates are divided into two grades based on differences in their development. Protostomes - Mollusks, annelids, arthropods, and several other phyla. Deuterostomes - Echinoderms, chordates and several other phyla. These differences center on cleavage pattern, coelom formation, and blastopore fate. 4

Developmental Difference between Protostomes and Deuterostomes