Ch 27 Mollusks and Annelids Flashcards
1
Q
what is phylum mollusca
A
- phylum Mollusca
- evolved 600 million years ago
- 100 000+ species
- 7 classes
- live across the world
2
Q
what are Mollusks
A
- 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
3
Q
what are the four body parts of mollusks
A
- 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
4
Q
how do mollusks feed
A
- 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
5
Q
how do mollusks breath
A
- Gill are used, sometimes within the mantle cavity
- some have a cavity of folding tissue that is lined with blood vessels to absorb O2
6
Q
how do mollusks respirate
A
- 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
7
Q
how do mollusks excrete waste
A
- excrete solid waste through the anus
- Nephridia eject ammonia from the body
8
Q
how do mollusks respond to stimuli
A
- 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
9
Q
how do mollusks reproduce
A
- 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
10
Q
what are snails, slugs, and relatives
A
- 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
11
Q
what are two shelled mollusks
A
- 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
12
Q
what are tentacled mollusks
A
- 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
13
Q
how do mollusks fit into our world
A
- 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
14
Q
what are annelids
A
- phylum Annelida
- Round, wormlike, with long segmented bodies
- range a lot
- 9000+ species
15
Q
how are annelids segmented
A
- septa or septum separate the segments
- most segments are the same, though some are different
