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58 Cards in this Set
- Front
- Back
adaptive radiation
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the evolution of many new species from a common ancestor...happens because new niches open up.
(as in molluscs...very diverse;some 50K extant, some 35K extinct, & and about 5% of all animals) |
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extant
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opposite of extinct...now living
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symmetry in molluscs?
Body type? |
bilaterally symmetrical, except gastropods (snails) because of internal twisting.
*primitive snail is bilaterally symmetrical Body type- they are unsegmented- no metamerism (repeated parts) |
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secondarily derived
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after that phylum evolved a mutation occurred and became a staple of that group
(like asymmetry in snails) |
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mollusks: what kind of coelom?
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eucoelom...like all the rest of the phyla we will study her on out (up the tree)
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3 features found in all mollusks?
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-muscular foot- for crawling, burrowing, grasping
-visceral mass- containing internal organs -mantle- secretes the calcium carbonate shell |
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what has the modifications has the mantle undergone in some mollusks?
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has been modified into gills, lungs, siphons, apertures, etc. in some mollusks
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Which mollusk developed the first "jaws"?
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nautilus
Nautilus also takes air and water into tube in shell to regulate and maintain buoyancy...remember video |
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Mollusks: dioecious or monoecious?
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most are dioecious, with the exception of the garden snail which is monoecious.
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What kind of development is found in mollusks? (direct/indirect)
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BOTH.
Cephalopods, gastropods and a few other mollusks have direct development, but all remaining mollusks have indirect development (trocophore larva) |
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Trocophore larva
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planktonic larva that emerges from mollusk egg.(also found in polychaetes (seg. worms) and marine turbilarians(flat worms))
-HOMOLOGY- branched off in larval stage, so ancestor of the group is the LARVA |
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mollusk nervous system?
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-several pairs of ganglia (ceregral, pedal, visceral)
*we saw these (3 little balls) on the squid dissection. -simpler than in the annelids & arthropod, with the exception of the octopus and squid which is the most advanced of any invertebrate |
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Cephalization in mollusks?
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-well developed in cephalopods and gastropods (predators)
-most others are grazers, scavengers or filter feeders with little need for external cephalization. |
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Excretory system in mollusks?
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well developed with 2 nephridia ("kidneys")
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circulatory system of mollusks?
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-OPEN system with pumping heart, blood vessels and blood sinuses whereby blood floods and is exchanged and returned to heart
-BUT, Cephalopods have a closed system of arteries capillaries and veins and 3 hearts. (like the squid's true heart and gill hearts we saw in lab) |
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mollusk respiratory system?
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most have GILLS, derived from the mantle tissue to increase the efficiency of gas exchange
-bivalves (clams, mussels) have incurrent and excurrent siphons |
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Biggest class in mollusks?
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gastropods 40,000 living species
then bivalves and polyplacophora |
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What class is the most primitive mollusk?
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Monoplacophora
- found on the ocean bottom, and thought of as extinct until the 1950's. -exhibit pseudometamerism- segmented gills NOT derived from segmentation |
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Polyplacophora
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Characterized by 8 dorsal plates.
found in inter-tidal zone grazing on algae. *Chitons are an example of polyplacophora. (share habitat with barnacles.) |
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What mollusk is commonly referred to as "tooth shells" or "tusk shells"?
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Scaphopoda
(look like a long tooth, with animal sticking out of "root") |
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What economically important mollusks are highly adapted for burrowing and filter feeding?
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Bivalvia
(2 shells- clams, oysters, etc.) |
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General characteristics of bivalves?
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-restricted to aquatic environments
- higher diversity of them in marine ecosystems, but many live in freshwater |
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Smallest and largest bivalves?
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-seed clam (looks like a pebble)
-giant clam (shell can achieve weight of 500 lbs) |
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Anatomy of bilvalve
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2 shells connected by HINGE LIGAMENT dorsally
-shell grows outward in rings from the UMBO (can count rings like on a tree to determine age) -foot is anterior (pulls animal forward) -siphons are posterior -ADDUCTOR muscles pulls shell together |
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Oldest clam found?
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400 years old.
-rings indicative of climate conditions throughout history |
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Adductor muscles?
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relax and contract to pull bivalve shells together/apart
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bivalve respiration
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-gills and all viscera suspended from dorsal interior surface of mantle cavity
- posterior incurrent and excurrent siphons create respiratory water flow |
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Digestive anatomy of bivalves?
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-GILLS used for filter feeding
(mucus on gills traps food particles) |
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freshwater Bivalve reproduction?
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-freshwater bivalve eggs are fertilized in SUPRABRANCHIAL CHAMBER above gills and develop in to GLOCHIDIA LARVA that parasitizes a particular species of fish.
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Glochidia larva
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released from freshwater bivalve onto fish.
we saw this in a video where bivalve creates a lure and spews glochidia out to attach to fish gills. (These don't harm the host.) |
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Reasons that freshwater bilvalves are the most endangered animals in the US?
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-dams & locks prevent fish migartion, so some host fish aren't present for reproductive glochidia.
-siltation & other water pollution foul thier filter feeding apparatus -overwhelmed by invasive mussels which eat all the food. -142 out of 300 native species are either extinct, endangered or soon to be listed as endangered. |
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marine bivalve reproduction?
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-fertilization is external
-there are 2 stages in marine bivalve fertilization (trochophore and veliger) diagram on p.197 of manual |
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What industry almost wiped out clam species along the Mississippi?
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the button industry.
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most common invasive bivalve in our region....
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Zebra mussel- Dreissena polymorpha
and Asian clam- Corbicula fluminea -mussels attach to boats,nets, docks, swim platforms, boat lifts, etc and can be transported on them (Zebra mussels can be microscopic veligers when they attach to the substrate & they are the ONLY freshwater mussel that attaches to objects) *Prevention: Report visible zebra mussels and clean boats. |
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What kind of symbiotic relationship is found in certain bivalves?
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the mantle tissue of some clams, such as the giant clam, contains photosynthetic zooxanthanella that provide much of the clam's nutrients!
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Formation of a pearl
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sand particle gets stuck between mantle and shell and the animal secretes NACRE (calcium carbonate in minute crystalline form) in concentric layers to reduce irritation.
*To make round man-made pearls, a round irritant is placed in between the shell and mantle. |
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Gastropoda
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means "stomach foot"
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largest molluscan class?
how many species? |
gastropoda (snails, slugs, whelks, nudibranchs, etc)
40K species! |
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What process in gastropods is responsible for moving the mantle cavity from the front to the back of the body?
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TORSION
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Torsion
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-in gastropods is responsible for moving the mantle cavity from the front to the back of the body.
-occurs during embryonic stage of life cycle -space above head allows for head to be drawn into mantle cavity, then foot forms barrier to outside. |
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What process in snails results in spiral winding of the visceral mass and shell?
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coiling
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How did "Coiling" evolve in snails and what is its advantage?
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-original symmetrical arrangement gave way to a CONISPIRAL shape, with shell to one side which resulted in the loss of the right gill.
*advantage- waste expelled from right side of cavity, reducing fouling of gills with waste |
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snail eyes and brain?
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-cerebral ganglia attached to nerve cord
-eyes are at the ends of tentacles, no hearing -Nocturnal. |
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"tongue with teeth" in snails?
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Radula
* it is also modified for feeding, shell boring/prying,harpooning and envenomating prey, chewing. |
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gypsobelum
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love dart fired by some snails, pre-copulation
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Gastropod reproduction
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monoecious
-sperm exchange - some use "lave darts" (gypsobelum) -eggs laid singly or attached to substrate as jelly mass -Direct development- hatchlings are mini adults |
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Which gastropod feeds on cnidarians and reuses the undischarged nematocysts?
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Nudibranchs "naked gills"
*no shell, but elaborate papillae covering the dorsal surfaces contain reused nematocysts. |
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papillae
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nodes containing reused nematocysts covering the dorsal surfaces of nudibranchs (marine gastropods)
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quirk of the Sea Hare...
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squirts copious (a lot) purple secretion from the PURPLE GLAND in their mantle cavity when provoked.
*marine gastropod. |
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Conus
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"cone shell"
marine gastropod that can be lethal to humans (or even other cone shells). stings its prey to paralyze it before consumption |
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4 main subclasses of class cephalopoda?
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Nautilus
cuttlefish squid octopus |
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Cephalopoda
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very derived but also very ancient.
-most extinct forms had exterior shells. -all are active predators. |
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advancements of cephalopods over other mollusks?
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well developed external cephalization
-foot modified into several tentacles with suckers -CLOSED circulatory system -complex reproductive behavior |
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Cephalopod nervous system?
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-sophisticated with external cephalization and large brain.
--sophisticated tactile, visual, olfactory and chemo sensory organs. -mantle with chromatophores and/or bioluminescence for camouflage and communication - very intelligent with sophisticated behaviors and communicationabilities. |
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chromatophores
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pigment-containing and light-reflecting cells.
Cephalopods can operate chromatophores in complex, wavelike chromatic displays, resulting in a variety of rapidly changing colour schemes. |
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eyes of octopi?
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has cornea, retina, iris, lens, 2 chambers
-Convergence with vertebrate eye structures |
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biggest eye?
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beloongs to Collosal Squid
this 46 ft 1000 lb squid has an eye with a 10" diameter! |
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repro in cephalopods?
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Sophisticated...
-males direct COLOR DISPLAYS directed at rival males. -spem encased in SPERMATOPHORES with one modified tentacle used to pluck the spermatophore from his own mantle cavity and insert it into the mantle cavity of the female. |