Ch 27 Mollusks and Annelids

Question 1

what is phylum mollusca

Answer 1

• phylum Mollusca
• evolved 600 million years ago
• 100 000+ species
• 7 classes
• live across the world

Question 2

what are Mollusks

Answer 2

• soft bodied animals that all have either an internal or external shell, aside from octopodes
• they have larva called trochophores which they share with annelids, trochophores are aquatic

Question 3

what are the four body parts of mollusks

Answer 3

• 4 parts: Foot, Mantle, Shell, and Visceral mass
  
  • the foot assists with eating and has the mouth, also facilitates movement
  • the mantle is a layer of tissue that covers the body
  • the shell is made of calcium carbonate and made by special glands
  • the visceral mass is behind the mantle and hast most of the organs

Question 4

how do mollusks feed

Answer 4

• display all mode of feeding across the various species
• slugs and snails have a radula, which is a straw like tongue covered in teeth that is supported by a cartilage rod, has various uses for feeding
• Certain sea slugs and cephalopods use jaws to bite food
• Some use poison or venom
• some like clams and oysters use gills to filter feed

Question 5

how do mollusks breath

Answer 5

• Gill are used, sometimes within the mantle cavity
• some have a cavity of folding tissue that is lined with blood vessels to absorb O2

Question 6

how do mollusks respirate

Answer 6

• Simple heart
• An open circulatory system is used for the more sessile ones, which goes into sinuses which then lead back into vessels
• Octopi and other motile taxa use closed circulatory systems

Question 7

how do mollusks excrete waste

Answer 7

• excrete solid waste through the anus
• Nephridia eject ammonia from the body

Question 8

how do mollusks respond to stimuli

Answer 8

• vary from, small ganglia near the mouth combined with simple cords as well as touch receptors, statocysts (help balance), and ocelli
• to very developed nervous systems in octopodes and their kin, developed brains and sense organs

Question 9

how do mollusks reproduce

Answer 9

• mostly separate sexes with external fertilization
• in tentacled mollusks along with some snails, the sperm is injected into the female
• some hermaphroditic snails exists, internal fertilization in both
• some oysters can switch sexes

Question 10

what are snails, slugs, and relatives

Answer 10

• class Gastropoda
• move with a big ventral foot
• many have one piece shells on their dorsal side
• various defense mechanisms: ink, hiding, shells, poison, nematocysts, bright colours

Question 11

what are two shelled mollusks

Answer 11

• Class Bivalvia
• oysters, clams, scallops
• free larva, sessile adults
• some burrow while other stick to objects
• scallops can flap to move
• glands make shells and pearls

Question 12

what are tentacled mollusks

Answer 12

• Cephalopods
• Octopi, Squid, Cuttlefish, nautiluses
• have tentacles (8), + 2 arms, or 38-90 in nautilus
• small internal shells, or no shells, except nautilus, squids have a flexible pen
• fast movement
• siphons move water
• ink and colour changing

Question 13

how do mollusks fit into our world

Answer 13

• predators and prey
• detritus feeders
• hosts to various parasites
• bivalves help monitor water
• research on cancer medication
• slugs + snails destroy plants
• shipworms destroy wood
• eating bivalves can poison you through red tide

Question 14

what are annelids

Answer 14

• phylum Annelida
• Round, wormlike, with long segmented bodies
• range a lot
• 9000+ species

Question 15

how are annelids segmented

Answer 15

• septa or septum separate the segments
• most segments are the same, though some are different

Question 16

how do annelids feed

Answer 16

• digestive tract or gut leads from mouth to anus
• various structures
• a pharynx holding jaws is common (held in mouth)
• some pharynxes are sticky, have various functions
• can filter feed with a mucus bag, or feather like fans

Question 17

how do annelids breath

Answer 17

• gills
• can also absorb through skin
• skin must stay moist

Question 18

how do annelids do internal respiration

Answer 18

• closed circulatory system
• 2 blood vessels travel the length of the body
• ring vessels move between side and go to organs
• a few ring vessels near the anterior region contract in a simple heart like function

Question 19

how do annelids excrete waste

Answer 19

• anus for solid
• tubes called nephridia eject others

Question 20

how do annelids do response

Answer 20

• pretty developed
• brain, 2 nerve, 2 ganglia
• a ventral nerve cord travels the length
• sensory tentacles, statocysts, chem receptors and eyes
• eyes vary from sports to full eyes
• others have simplified sensors, ex earth worms

Question 21

how do annelids defend themselves

Answer 21

• burrow for defense, some make CaCO3 tubes
• some have jaws or spines for defense

Question 22

two do annelids move

Answer 22

• longitudinal muscles contract the body
• other wrap around and make it skinnier

Question 23

how do annelids reproduce

Answer 23

• mostly sexual
• vary, separate sexes or hermaphrodites, internal or sexual

Question 24

what are sandworms, bloodworms, and relatives

Answer 24

• class Polychaeta (many bristles)
• Many aquatic species
• have paired paddle like appendages with bristles
• burrow, hide, swim, or make tubes

Question 25

what are earth worms and their relatives

Answer 25

- class Oligochaeta - Live in soil or water - less bristles

Question 26

what are leeches

Answer 26

- class Hirudinea - Live in tropics, mostly freshwater - most are less than 6 cm, some 30cm or more - external parasites that drink blood, some carnivores - powerful suckers on both ends - muscular proboscus punctures flesh, pharynx sucks blood - some produce anesthetics

Question 27

how do leeches fit into our world

Answer 27

- plankton host many larva - diets of many organisms - condition soil, aerate - decomposers