Presentation on theme: "Mollusks Belong to phylum Mollusca which means “soft” in Latin."— Presentation transcript:
1 Mollusks Belong to phylum Mollusca which means “soft” in Latin. 2. They are soft-bodied animals that usually have aninternal or external shell.3. Includes snails, slugs, clams, squid and octopi.4. They all share similar developmental stages.-many aquatic mollusks have a larval stage calleda trochophore.-annelids also have trochopore larvae indicating thetwo groups are closely related.
2 Body PlanThe body plan of mollusks has four parts:a. Foot- for movementb. Mantle- thin layer of tissue that covers the body.c. Shell- made by glands in the mantle.d. Visceral mass- consists of internal organs.FeedingMollusks can be herbivores, carnivores, filterfeeders, detritivores, or parasites.2. Snails and slugs feed using a flexible, tongue-shaped structure called a radula.-has hundreds of tiny teeth to scrape algae or drilla hole through shells of animals to eat the prey’ssoft tissue.
3 3. Octopi and certain sea slugs use sharp jaws to eat their prey.-some octopi produce poisons.4. Shellfish use feathery gills for filter feeding.-food enters with water through a tube called theincurrent siphon. -small food items become trapped in the stickymucus of the gill.-water exits the shellfish out the excurrent siphon.RespirationAquatic mollusks breathe using gills inside theirmantle cavity.2. Land snails and slugs must keep their mantle cavitymoist so gases can diffuse with the blood stream.
4 CirculationOxygen and nutrients are carried by a circulatorysystem.a. can be an open circ. system- blood leaves vesselsand empties into a sinus (large saclike space).-work well for slow moving mollusks with lowoxygen demand.b. closed circ. system- blood remains in vessels.-more efficient delivery system for faster-movingmollusks like squid and octopi.Excretion1. Tube-shaped nephridia remove ammonia from theblood and release it outside the body.
5 ResponseComplexity of the nervous system varies greatlyamong mollusks.2. Clams and other two-shelled mollusks just havesmall ganglia near the mouth, a few nerve cords,and simple sense organs (chem. receptors,eyespots)3. Octopi and relatives are active, intelligent predators.-they have the most highly dev. nerv. system of allinvertebrates.-have highly dev. brains capable of remembering.MovementSnails and slugs secrete mucus and glide across it.Clams burrow with a hatchet-shaped foot.
6 3. Fast moving squid and octopi use jet propulsion. -water is drawn in mantle cavity and then forcedout through a siphon.ReproductionSome mollusks are hermaphrodites.Many snails and two-shelled mollusks releaseenormous numbers of eggs and sperm into thewater. (external fertilization)3. In tentacled mollusks and some snails fertilizationis internal.
7 Groups of Mollusks**Mollusks are divided into several classes accordingto characteristics of the foot and the shell.Class GastropodaSnails, slugs, sea hares, limpets, nudibranchs arecommonly called gastropods.2. They are shell-less or single shelled mollusks thatmove by a muscular foot on the ventral side.3. Snails can completely withdraw into the shell forprotection and seal it with a hard plate.-also prevents evaporation during drought.4. Sea hares can squirt ink to confuse predators.
9 5. Some nudibranchs have chemicals that make them taste bad or are poisonous.-their bright colors serve as warnings.Class BivalviaBivalves have two shells that are held together bypowerful muscles.2. Includes clams, oysters, mussels, scallops.3. Can burrow into sand and mud or secrete stickyfibers to attach to rocks.4. Scallops can move around by clapping theirshells together.5. Filter-feeding bivalves use mucus and cilia on theirgills to trap food particles in the water.6. Irritants can be coated with “mother-of-pearl .”
11 Class CephalopodaCephalopods include octopi, squid, cuttlefish, andnautiluses.2. The head is attached to a foot that divides intomany tentacles.3. Most have small internal shells or no shells at all.4. The nautilus has an external shell and up to 90tentacles.-gases can be secreted into the shell to controlit’s buoyancy.5. They have highly developed brains and senseorgans.
13 Ecology of Mollusks Mollusks are an important food source for many organisms including humans.2. Bivalves form many symbiotic relationships withbacteria and algae.3. Since bivalves are filter-feeders they can act asenvironmental monitors by checking their tissuesfor dangerous pollutants and microorganisms.4. Snails are being studied as to why they neverdevelop cancer to gain insight into how to fightcancer in humans.
14 Annelids Members of Phylum Annelida are more related to mollusks than they are to flatworms or roundworms.-have a similar larval stage with mollusks.2. The name Annelida is Latin for “little ring,” referingto the ringlike appearance of body segments.3. Their bodies are divided into segments that areseparated by internals walls called septa.4. In many annelids bristles called setae are attachedto each segment.5. They have a true coelom lined with mesoderm.6. Food passes from mouth to anus (tube-within-a tube)
15 Feeding and DigestionAnnelids range from filter feeders to predatorycarnivores.2. Many feed using a pharynx which is a muscularstructure which draws in food.3. In earthworms food then moves to a storage organcalled the crop.4. Food then passes to a solid organ that grinds thefood called the gizzard.5. Food is then passed to and absorbed by theintestine.
16 Circulation1. Annelids have a closed circ. system.-blood iscontained in a network of blood vessels.2. In earthworms blood circulates through two majorblood vessels that run from head to tail.-the dorsal (top) blood vessel moves blood towardthe head of the worm.-blood in the ventral (bottom) blood vessel runsfrom head to tail.3. Each body segment has a pair of smaller bloodvessels called ring vessels that connect thedorsal and ventral vessels.-these supply blood to the internal organs.-five pairs of ring vessels near the anterior endfunction as hearts by pumping blood.
17 RespirationAquatic annelids breathe through gills.Land dwelling annelids undergo gas exchangethrough their skin and bloodstream by diffusion.-suffocate if skin dries out and will drown ifsubmerged under water for too long.ExcretionDigestive waste passes out the anus.Cellular waste containing nitrogen is eliminatedby small tubes called nephridia.ResponseMost annelids have a well developed nervous sys.2. An anterior brain is connected to several nervecords.3. Marine annelids can have many sense organs.
18 MovementAnnelids have two major groups of muscles thatfunction as part of a hydrostatic skeleton.a. Longitudinal muscles run front to rear and cancontract to make the worm shorter and fatter.b. Circular muscles wrap around each segment andcan contract to make the worm thinner and longer.2. Marine annelids have parapodia- paddelikeappendages for swimming and crawling.ReproductionMost reproduce sexually.2. Some use internal external fertilization and haveseparate sexes.
19 3. Some like earthworms and leeches are hermphrodites.4. Two worms attach to each other and exchangesperm and store it in special sacs.-when eggs are ready for fertilization the clitellumsecretes a mucus ring into which eggs and spermare released.-ring slips off worms body and forms a cocoon.-young worms hatch a few weeks later.
20 Groups of Annelids Class Oligochaeta Oligochaetes include earthworms and their relatives.Their class name means “few hairs” because theytypically have only a few setae.3. Most live in soil or fresh water.4. Earthworms leave squiggles of mud above groundcalled castings.-this is the undigested material that has passedthrough the body and out the anus.5. Earthworms help enrich and aerate the soil.6. Earthworms scientific name is Lumbricus terrestris.
22 Class HirudineaContains the leeches.Typically external parasites that suck blood of host.Some are carnivores that feed on worms, snails,insects larvae.4. The posterior sucker is used for attaching to objectsand the anterior sucker sucks the blood.5. Some leeches extend a muscular structure calleda proboscis into the host.6. Others slice into the host with razor sharp jaws.7. Leeches release a substance that anesthetizesthe wound.8. Leeches are still used for medicinal purposes.
23 Fear factor leech scene “What are you doing?”“Feeding my pets!”
24 Class PolychaetaClass name means “many hairs.”Marine annelids that have paired, paddlelikeappendages tipped with setae.-form brushlike, feathery structures which give thisclass it’s name.-these setae or bristles can be used for defense,breaking off when touched causing irritation andburning.3. Examples are sandworms, bloodworm, fireworms.
26 Ecology of Annelids Annelids are important parts of food chains. Earthworm burrows provide passageways for plantroots and water.
27 Echinoderms Examples: sea stars, sea urchins, sand dollars, sea cucumbers, sea lilies, feather stars, brittle stars.2. Belong to phylum Echinodermata which means“spiny skin.”-their skin is stretched over an endoskeleton ofhardened plates of calcium carbonate.3. They live only in the sea.4. Typically have no anterior or posterior end andlack cephalization.5. Bodies are two-sided:-oral surface- mouth side-aboral surface- opposite side.
28 6. Most adult echinoderms exhibit five-part radial symmetry.-the larvae have bilateral symmetry.7. Echinoderms are more closely related to vertebratesthan any other animal phyla.-echinoderms and vertebrates are deuterostomes-the blastopore develops into an anus.-all other animal phyla are protostomes- theblastopore develops into the mouth.-a blastopore is the opening of the blastula—a hollowball of cells that forms from the zygote.8. Echinoderms have a unique water-vascular system:-system of internal tubes filled with fluid that carryout respiration, circulation, and movement.
29 -it opens to the outside through a sievelike structure called the madreporite.-this leads to a ring canal that forms a circle aroundthe mouth of sea stars.-five radial canals extend along each arm from thering canal.-attached to each radial canal are hundreds ofsuction-cuplike structures called tube feet.FeedingSea urchins scrape algae from rocks.Sea lilies use tube feet to capture floating plankton.Sea cucumbers are detritus feeders.Sea stars are carnivores on mollusks:
31 -pry open mollusk shell, invert stomach into shell, release enzymes and digest the mollusk in itsown shell.Respiration and CirculationOxygen, food, and wastes are carried by thewater-vascular system.2. The thin-walled tissue of the tube feet provide themain surface for respiration.ExcretionSolid wastes are expelled through the anus.Nitrogen cellular wastes are passed into the waterthrough the thin-walled tube feet.
32 ResponseSince they have no head, they have no brain.They have a nerve ring that surrounds the mouth.Radial nerves connect the ring with body sections.Have sensory cells that detect light, gravity, etc.MovementMost move using tube feet and thin layers of muscleattached to their endoskeletons.ReproductionReproduce by external fertilization.Most species have separate sexes.
33 Groups of Echinoderms Sea Urchins and Sand Dollars They both have large, solid plates that form a boxaround their internal organs.2. Most eat large amounts of algae.3. Sea urchins can have long, sharp spines.
34 Brittle Stars1. Have slender, flexible arms and can move rapidly.2. Can easily shed one or more arms when attacked.3. They are detritivores and filter feeders.
35 Sea CucumbersLook like warty, moving pickles.Most are detritus feeders sucking up organic matteralong the ocean floor.
36 Sea StarsCan regenerate lost arms.Can regenerate into a new animal if the piececontains a portion of the central body part.
37 Sea Lilies and Feather Stars Filter feeders with long, feathery arms.Oldest class of echinoderms.