Unit 11 Mollusks and Echinoderms Guided Notes

Molluks

General Characteristics of Mollusks

________________ are a very diverse group of animals that

____________________________________________________.

They contain members that are ___________________________

____________________________________________________.

However, all have _____________________________________.

These body parts are the ________________________________

____________________________________________________

_______________________________________. The _________

____________________________________________________

for those molluscs that have one.

Phylum Mollusca is made up of over 112,000 species of soft-bodied animals. These

animals generally exhibit _________________________________________________

___________________________________ as well as the three main body parts

(visceral mass, foot and mantle) introduced above. Mollusks _____________________

______________________________________________________________________

_______________________________________________. Many mollusks have

_______________________________. Nitrogenous waste is excreted through

_______________________. Mollusks have an _______________________________

with a dorsal heart and vessels. The hemocoel aids fluid return to the heart. A _______

________________________________________________________ (a flexible

tongue like strip of tissue covered with tough abrasive teeth that point backward). The

radula is used to graze, drill, or function as a poisonous dart. The nervous system has a

______________________________________________________________________

_______________________________________ with the development of the

_______________________________________ (nearly indistinguishable from

annelids). The trochophore larvae becomes the veliger larvae for swimming.

Mollusks are true ___________________________ with a reduced main body cavity

called the hemocoel. They are also Protostomes so the mouth develops first in the

embryo.

There are four main classes of Mollusks that we will study in this unit. They are

Amphineura (polyplacophora), Bivalvia, Gastropoda, and Cephalopoda.

The Chitons

The Chitons belong to Class ____________________________________________.

Chitons are ___________________________________ with a shell that is made up of

________________________________________________. They have a muscular

foot for locomotion (crawling). Chitons have a reduced head. There are about 650

species of these organisms. They can be found clinging to rocks in the intertidal zone

and use a tooth-like radula to scrape food off

of rocks. Chitons are herbivores.

Breathing is facilitated by ____________.

........

Gastropods Class __________________________________ has adapted their foot so it is located on their ventral surface or belly. This is the largest molluscan class and includes _______ _______________________________________. They are characterized by a ______________________ with the characteristic cone shape or no shell. Gastropods __________ __________________________________________________ __________________________________________________. The muscular foot extends along the ventral surface of the

organism. Gastropods undergo a process called _______________ during larval development. In torsion the visceral mass twists 180 degrees in relation to the head. This results in the mantle cavity, gills and anus being brought to the front of the animal. This allows the gastropod to retract its head into its mantle cavity when threatened. The head of gastropods contains __________________________________________ ____________________________. A scraping ________________ is used to pick up food. Slugs do not have a shell. They _______________________________________ ____________________________________. They usually become active during the cool moist part of the day. Gastropods are the only molluscan class to become terrestrial. Gastropods have an ________________________________________________ with a circulatory fluid called hemolymph.

Nudibranchs (Sea Slugs) are marine gastropods that lack shells. Nudibranch means “naked gill” and refers to the fact that gas exchange happens across the entire surface of these animals. The images below show how these animals maximize their surface area and their vivid colours.

Bivalves

The name ____________________________________________

_____________________________________________________

_____________________________________________________.

The mantle of a bivalve is responsible for excreting the shell to

surround and protect the body. Strong muscles hold the shell

closed in all members to the class. The muscular foot varies from

bivalve to bivalve. It is most prominent in the clam which uses its

large muscular foot to dig through the sand. Scallops can move by

jet propulsion and swim through the water escaping predators such

as sea stars. An oyster's shell will grow directly on a rock to provide

a permanent home. __________________________ but here is a scallop swimming.

Bivalves are ________________________

animals and live in the intertidal zone.

They exhibit a large visceral hump and a

muscular foot with a reduced head covered

with a thin mantle. __________________

_________________________________

_________________________________

_________________________________.

Bivalves are _______________________

and take water containing food into the

mantle cavity via the incurrent siphon and

pass it over the mouth. Excess water is

forced out through the excurrent siphon. The _________________________________

_____________________________________________________________________.

They have no radula. The general anatomy of a clam is shown above as an example of

a bivalve.

Respiration is performed by the

________________________

________________________

________________________

________________________.

This food then passes the

________________________

________________________

__________________, where it

follows an ________________

________________________.

Food is digested in the stomach

and then passes to the

__________________ for

absorption. The intestine is a

long coiled organ ending in an __________ where the waste is expelled. Also found in

the visceral mass is the heart. The _________________________________________

_________________________________ to supply it with oxygen and remove nutrients

and wastes.The diagram below shows the circulatory system of a clam. Recall,

___________________________________________________________________

with a dorsal heart and vessels.

Geoducks burrow in the sand

or amongst rocks or attach to

substrate by secreting byssal

threads. They many leap with

a foot. They have separate

sexes and external fertilization

............Mmmm oysters!

....

Clam Anatomy Review Exercises

Cephalopods

The name ____________________________________________________________ are given this term because the _________________________ ________________________ ________________________. All members of this class are __________________. Of the invertebrates, it can be argued that the __________________ ________________________. This is because of their _________________________ _________________________. Their ability to learn and muscular control are so advanced that they can be trained to open jars to obtain food. They have quite an ________________________ that is distinctly different from that of a human.

The cephalopods are also fast swimmers and ________________________________

___________________. To generate this propulsion they take water in slowly and expel it so quickly that they are propelled forward. Other features of cephalopods include a _______________________________ and a ________________ which is a toothed tongue. Many of the animals that an octopus typically feeds on have either a shell or an exoskeleton so the chitinous beak is necessary for feeding. For predator diversion the cephalopods posses an ____________________ _______________________________________. Cephalopods contain ______________________ _______________________________________ _______________________ which enable them to change color. The octapus puts this skill to good use as ________________________ and the cuttlefish uses colour change to attract a mate and warn off the competition all at the same time. Here is a part of a TED video with a great octapus camouflage video.

.......

Cephalopods have __________________________________________________________. Their circulatory system is a __________________________________________, so the circulatory fluid is contained within the vessels. Jet propulsion can be used to escape predators by forcing water out a siphon. ____________________________________________________ ____________________________________________________________________. Sexual reproduction results in internal fertilization followed by egg laying.

Echinoderms

General Characteristics of Echinoderms

____________________________________________________________________________________________________________________________________________. This means that the first embryonic opening becomes the anus and the second becomes the mouth. Because of this trait, it is thought that echinoderms are more advanced than some of the other animals. However, ___________________________ __________________________________________. For example, their ___________

__________________________ would usually be considered more primitive than bilateral symmetry, so it is difficult to see their relation to the vertebrates. Also, echinoderms have ____________________________, and have a ________________ for controlling motor and sensory functions. However, when in larval form, an echinoderm is a free swimming bilaterally symmetrical organism. It is this larval form that scientists believe evolved into some of the prochordates that are mentioned later in this course. Echinoderms are fairly diverse in appearance within the phylum. Typified by the ______________________________________________________________________________________________________________ they vary in outer appearance but have similar internal structures . They are ____________________________________ and can be found from the intertidal zone to deep ocean waters. The digestive system is relatively short, and digestive glands are located within the arms of the starfish, or on the outer body wall of the other members. Digestion, however, is a bit different from other animals, in that, much of it takes place outside the body of the starfish. The echinoderm will put its stomach outside of its body and begin to digest its prey before it takes it in to finish the process. They can be __________________________________. Sex organs are also located in the arms of the starfish, and echinoderms are capable of both _____________________________________________. External reproduction ____________________________________________________________________________________________________________________. The regeneration properties of starfish allow them to regrow lost limbs as well as the limb to regrow a body. _____________________________________________________________, are found throughout the body wall providing the echinoderm with oxygen. The method of locomotion in the starfish is truly unique. The _____________________ _______________________________ is a network of tubes ending in ______________. An organ called an __________________ will pump water into the tubes increasing the pressure in the tube foot causing it to expand and create suction on a nearby surface. As the pressure on the tube foot decreases, the tube contracts without decreasing the suction, and the starfish is pulled in that direction.

Class Asteroidea Sea Stars have __________________________ with several arms (5 or multiple of 5) radiating from a central body. The _________________________________________________ ________________________________________________. The anus is at the center of the disc together with the water intake (__________________). The upper surface is often very

colorful with ________________________________ ______________________________________________ ______________________________________________ ____________________________________________. Sea stars have a ________________________________

_________________________________________ _______________________________________ to allow movement. Sea stars have ______________ ________________________________________. They have a ______________________________. Reproduction is __________________ with most species having separate sexes. Free swimming larva called bipinnaria are produced. Sea stars are ________________________ and feed on and

externally digested their food. The picture below shows a sea star feeding on a bivalve. Notice all the tube feet at work. They also have two stomachs. Food moves first into the ________________________ ______________________________.

Sea stars also exhibit the ability to regenerate body parts......flip themselves over..even with an arm missing.

Sea Star Review Exercises

Class Crinoidea (feather stars)

Feather stars have _______________________________. The body of a typical feather star is cup-shaped with ____________________________________________ ____________________________________________________ __________________. Some have five arms while others may have as many as 200. The arms, called pinnules, are coated with a sticky substance that helps them catch food. Cirri attached to the underside of the body. The mouth and their anus are situated on the upper side of the feather star. Below is a video of a feather star swimming. ........

Class Ophiuroidea (brittle stars) _______________________________________________ ___________________________________. They have _______________________________ with a central disc and five highly flexible arms that protrude. Unlike sea stars, there is no replication of internal organs in each arm just one set in the central disk. Brittle stars have a much smaller central disc and no anus. Wastes are eliminated through the mouth which is situated on

the underside in the center. On the underside of the body disk there is an opening at the base each arm on both sides. These ten openings are breathing and reproductive outlets. They take in water to gain oxygen and shed eggs or sperm into the sea. ..........

Class Echinoidea (sea urchins) Sea urchins have a ____________________________________ body and an external _______________________________________. The mouth consists of a complex arrangement of muscles and plates surrounding the circular opening. Sea urchins have a centrally located jaw (called Aristotle's lantern) with

horny teeth. The anus is located on the upper surface. Some sea urchins have a spherical, bulb-like cloaca to store fecal material. The cloaca protrudes from the anal opening and can be withdrawn into the shell. Sea urchins have movable spines of various sizes and forms that are attached to the body. _________________ __________________________________________. They also have _____________ _____________________________________. Some of these pedicellaria are poisonous. ........

Class Holothuroidea (sea cucumbers) _____________________________________________________ _________________________________________ unlike most other Echinoderms that display radial symmetry. Sea cumcubers have a distinct dorsal and ventral side or back and bottom. They are cucumber shaped with an elongated, muscular, and flexible body. The mouth is at one end and the anus is at the other. Around the mouth there are _______________________________ _______________________________- used in food collecting. These tentacles are modified tube feet. Here is a sea cucumber feeding.