Zoology Test 2d

Question 1

adaptive radiation

Answer 1

describes the evolution of many new species from common ancestor

Question 2

mollusc origins

Answer 2

• originated in ocean, but now in almost every freshwater and terrestrial habitat
• very large phylum
• 50,000 extant species
• 35,000 extinct species

Question 3

symmetry of mollusc

Answer 3

• bilaterally symmetrical
• some have secondarily derived asymmetry
• contains eucoelomate

Question 4

general characteristics of mollusc

Answer 4

• muscular foot for crawling, burrowing and grasping
• visceral mass which contains internal organs
• mantle which secretes calcium carbonate shell
• soft unsegmented body

Question 5

reproduction in mollusc

Answer 5

• most dioecious, some monoecious

- some have direct and some have indirect development

Question 6

Development in mollusc

Answer 6

• mostly direct development

- larvae stage though is trocophore larvae

Question 7

nervous system in mollusc

Answer 7

• several pairs of ganglia
• cerebral, pedal and visceral
• generally simpler than that found in anthropoids
• system of cephalopods is most advanced in any vertebrate

Question 8

trocophore larvae

Answer 8

• found in annelids, platyhelminthes

- homology; indicate genetic relationship

Question 9

cephalization in molluscs

Answer 9

• cephalopods and gastropods
• most others are grazers, scavengers or filter-feeders with little need for external cephalization
• usually have “foot”

Question 10

excretory system in molluscs

Answer 10

• contain two nephridia

Question 11

circulatory system in molluscs

Answer 11

• open system with pumping heart, blood vessels and blood sinuses whereby blood returns to heart
• cephalopods have closed system of arteries, capillaries and veins, complex with three hearts

Question 12

respiratory system in molluscs

Answer 12

• most have gills derived from mantle tissue to increase efficiency of gas exchange
• incurrent and excurrent siphons present in bivalves

Question 13

molluscs

Answer 13

• Monoplaophora
• Polyplacophora
• Scaphopoda
• Bivalvia
• Gastropod
• Cephalopod

Question 14

Monoplaophora

Answer 14

• primitive mollusc
• found on ocean bottom known only as fossil
• exhibit pseudometamerism (segmentation)

Question 15

Polyplacophora

Answer 15

• characterized by 8 dorsal plates
• found in intertidal zone of seacoasts
• feed by grazing on algae on rocks

Question 16

Scaphopoda

Answer 16

commonly referred to as “tooth shells” or “tusk shells”

Question 17

Bivalvia

Answer 17

• large, economically important class of mollusks
• highly adapted for burrowing
• filter-feeding
• clams, oysters, mussels, limpets, periwinkles, scallops
• restricted to aquatic environments
• most diverse in marine systems, but many freshwater

Question 18

anatomy of bivalvia

Answer 18

• two shells connected by hinge ligament
• shell grows outward in “rings” from umbo
• foot extends anteriorly from shell to put animal forward
• adductor muscles pull shells together

Question 19

respiration in bivalvia

Answer 19

• gills suspended from dorsal, interior surface of mantle cavity
• posterior incurrent and excurrent siphons create respiratory water flow

Question 20

digestion in bivalvia

Answer 20

• gills also used for filter feeding

- mucus on gills traps food particles

Question 21

reproduction in freshwater bivalve

Answer 21

• freshwater bivalve eggs fertilized internally in suprabrachial chamber above the gill
• eggs develop into glochidia larvae that parasitize a particular species of fish

Question 22

reproduction in marine bivalve

Answer 22

• fertilization is external
• 2 larval stages
• one larval stage being the trochophore larvae

Question 23

endangered bivalves

Answer 23

• dams and locks prevent fish migration so some can’t reproduce because their host fish aren’t present
• siltation and other forms of water pollution foul filter-feeding apparatus
• being overwhelmed by introduced mussels, which filter food
• poaching for pearl industry
• 184 of 300 native species are extinct, endangered or soon to be endangered

Question 24

invasive bivalves

Answer 24

• zebra mussel (Dreissena polymorpha)

- Asian clam (Corbicula fluminea)

Question 25

Is there a symbiotic relationship in certain bivalves? And if yes, what?

Answer 25

yes, mantle tissue contains photosynthetic zooxanthellae that provide much of clam's nutrients and color

Question 26

pearls

Answer 26

produced by secreted fluid from the mantle called nacre that smooths out irritations (sand)

Question 27

Gastropoda

Answer 27

- largest by far in terms of number of recognized species | - 70,000 living species

Question 28

gastropod body plan

Answer 28

- torsion - coiling - lost organs, doesn't seem to bother them that they have lost organs - radula

Question 29

torsion

Answer 29

- is responsible for moving mantle cavity from back to front of body - occurs before hatching - space available in mantle cavity allows animals head to be withdrawn into shell for protection, foot forms barrier to outside

Question 30

coiling

Answer 30

- spiral winding of visceral mass and shell - original symmetrical arrangement gave way to conispiral shape, with shell to one side, which resulted in loss of gill on right side - advantage: wastes expelled from right side of mantle instead of over head

Question 31

radula

Answer 31

- rasping/grasping organ in mouth - "teeth" - modified for feeding, shell prying, harpooning and envenomating prey, chewing

Question 32

reproduction in gastropod

Answer 32

- monoecious - sperm exchange with internal fertilization - some use dart to puncture mate - eggs laid singly or attached to substrate - larval stages occur before hatching - hatchlings are miniature adults (direct development)

Question 33

gastropod diversity

Answer 33

- nudibranchs - sea hare - conus (cone shell)

Question 34

sea hare

Answer 34

marine gastropod squirts copious purple secretion from purple gland in mantle cavity when provoked

Question 35

nudibranch

Answer 35

- nudibranchs feed on cnidarians and reuse undischarged nematocysts - elaborate papillae covering their dorsal surfaces contain reused nematocysts

Question 36

conus

Answer 36

- marine gastropod stings its prey to paralyze before consuming - can kill other cone shells or humans

Question 37

Cephalopods general characteristics

Answer 37

- nautilus - octopus - squid - cuttlefish - very derived molluscs but very ancient too - most extinct forms had exterior shells - active predators

Question 38

advancements of cephalopods

Answer 38

- well-developed external cephalization and foot modified into series of tentacles and suckers - completely closed circulatory system - complex reproductive behavior

Question 39

Cephalopod reproduction

Answer 39

- very sophisticated - males undergo color displays directed against rival males - sperm encased in spermatophores - one modified tentacle used to pluck spermatophore from own mantle cavity and insert into mantle cavity of female

Question 40

Cephalopod nervous system

Answer 40

- sophisticated nervous system - sophisticated sensory organs - tentacles with tactile and chemosensory cells - mantle with chromatophores or bioluminescence for camouflage and communication - intelligent with sophisticated behavior - complex communication abilities - contain eyes