Chapter 35 Study Guide
head-foot region, visceral mass
2 regions of mollusks
Polyplacophora
600 species of sedentary mollusks with 8 overlapping plates
adductor muscles
A bivalve can close its shell by contracting their powerful ______ that are attached to the inside surface of each valve.
filter feeders
As an adaptation for a sessile existence, bivalves usually are ______.
common ancestor
Because both Annelida and Mollusca have trochophore stages, it is inferred that they have a _____.
radula
Bivalves are the only mollusks without a ______.
diecious
Cephalopods are diecious/hermaphroditic
free-swimming, predatory
Cephalopods are specialized for a ______, _______ existence.
closed
Cephalopods have a ---- circulatory system.
Soil is sucked into the mouth by the muscular pharynx. The soil then passes through a tube called the esophagus to a temporary storage area known as the crop. From the crop, the soil moves to a thick, muscular part of the gut called the gizzard. The gizzard grinds the soil, releasing and breaking up organic matter. As the soil passes through the long intestine, digested organic compounds and nutrients in the soil are absorbed by the blood. An infolding of the intestinal wall called the typhlosole increases the surface area available for digestion and absorption. Undigested material is eliminated from the earthworm's body through the anus.
Describe feeding and digestion in an earthworm
The worm anchors some of the middle segments by their setae and contracts the circular muscles in front of those segments. Contraction of the circular muscles increases the pressure of coelomic fluid in those segments. This increased pressure elongates the animal and pushes the anterior end forward. Setae in the anterior segments then grip the ground as the longitudinal muscles contract, pulling the posterior segments forward.
Describe locomotion in an earthwrom
The blood travels toward the posterior end through a ventral blood vessel and then returns to the anterior end through a dorsal blood vessel. Five pairs of aortic arches link the dorsal and ventral blood vessels near the anterior end of the worm. Contractions of the dorsal blood vessel and aortic arches force blood through the circulatory system
Describe the circulatory system of an earthworm
open
Gastropods have an ____ circulatory system.
By decomposing dead leaves and other organic materials, earthworms help release nutrients into the soil and maintain its fertility. The burrows made by earthworms allow air to penetrate into the soil, bringing oxygen to plant roots and soil microorganisms. Earthworms also loosen the soil, making it easier for roots to grow and for water to seep into the soil.
How do earthworms help soil?
sessile
In contrast with gastropods, which move about in search of food, most bivalves are ______.
mucous plug
In dry periods, snails seal the opening to their shell with a _____, which keeps them from drying out
winglike flap
In sea butterflies, the foot is modified into a __________ that is used for swimming rather than crawling.
dark fluid
Many cephalopods can release a ----- into the water to temporarily distract predators
eight
Octopuses have ___ tentacles
ten
Squids have ___ tentacles
nervous system
The ---- is more advanced in cephalopods than in any other group of mollusks.
trochophore
Unlike other mollusks, cephalopods develop from an egg into a juvenile without becoming a ----.
"many bristles"
What does polychaeta mean?
marine
_____ clams undergo external fertilization.
freshwater
_____ clams undergo internal fertilization.
chitin
a carbohydrate that forms part of the cell walls of fungi and part of the exoskeleton of arthropods, such s insects and crustaca
trochophore
a free-swimming, ciliated larva of many worms and some mollusks
cephalopod
a marine mollusk that has tentacles extending from the head; an octopus, squid, cuttle-fish, or nautilus
ganglion
a mass of nerve cells
gastropod
a mollusk that has a well-developed head and a flattened foot, such as a snail, slug, or conch
siphons
a pair of hollow, fleshy tubes found in a clam
torsion
a process by which the visceral mass twists around 180 degrees in relation to the head, bringing the mantle cavity, gills, and anus to the front of the animal
radula
a rasping, tonguelike organ that is covered with chitinous teeth and that is used for feeding by many mollusks
crop
a sac or pouch used by birds and some insects to store food
seminal receptacle
a saclike organ of female or hermaphroditic invertebrates that stores sperm
incurrent siphon
a tube through which water enters the body of a bivalve
excurrent siphon
a tube through which water exits the mantle cavity of a bivalve
nephridium
a tubule through which some invertebrates eliminate wastes
able to move without hindering movement of food through gut; space for circulatory system to transport blood without interfering with other organ systems
advantages of coelom
surface area
although shells protect the soft bodies of mollusks and predators, they also reduce the ______ available for gas exchange.
bivalve
an aquatic mollusk that has a shell divided into two halves connected by a hinge, such as a clam, oyster, or mussel
gizzard
an enlargement of the digestive tract of some invertebrates, such as annelids and insects, that grinds food
typhlosole
an infolding of the intestinal wall that increases the surface area available for digestion
coelomates
animals with a true coelom, a hollow, fluid-filled cavity that is completely surrounded by mesoderm
oysters
bivalves that become permanently attaches to a hard surface early in their development
clams
bivalves that live buried in mud or sand and have siphons
clams, oysters, scallops
bivalvia examples
octopuses, squids, cuttlefishes, chambered nautiuses
cephalopoda examples
brains
cephalopods have the largest ___ of invertebrates
octopuses
cephalopods with eight tentacles that share many characteristics with squids, including methods of escaping predators; instead of using jet propulsion to chase prey, more likely to crawl along the ocean bottom with their tentacles or lie in wait in caves and rock crevices
Polychaeta
class of annelids that have numerous setae to help them move, which project from parapodia, some of which help them in gas exchange; have antennae and specialized mouthparts; trochophore stage; marine habitats
Oligochaeta
class of annelids that live in the soil or in fresh water and have no parapodia and only a few setae in each segment.
sea butterflies
common name for pteropods
a chain of ganglia connected by a ventral nerve cord. Most body segments contain a single ganglion. nerves branching from each ganglion carry impulses to the muscles and from the sensory cells in that segment. in the most anterior segments, several ganglia are fused to from the cerebral ganglia
describe an earthworm's nervous system
Two earthworms press their ventral surfaces together with their anterior ends pointing in opposite directions. The worms are held together by their setae and by a film of mucus secreted by each worm's clitellum. Each earthworm injects sperm into the mucus. The sperm from each worm move through the mucus to the seminal receptacle of the other, where the sperm are stored. The worms then separate. After several days, the clitellum of each worm secretes a tube of mucus and chitin. As this tube slide forward, it picks up the worm's eggs and the stored sperm from the other worm. Fertilization occurs inside the tube, which closes up to form a protective case. The young worms develop inside the case for 2-3 weeks before hatching
describe reproduction in earthworms
slugs, nudibranchs
gastropods that have no shell example
snails, abalones, conchs
gastropods that have single shells examples
Architeuthis
giant squid that can reach a length of 18 m
trap food, exchange gases
gills function
after attaching themselves to the skin of their host, parasitic leeches secrete an anaesthetic that prevents the host from feeling their presence. They also secrete a substance that prevents blood from clotting; can take 10x its weight in blood
how are leeches specialized for parasitism?
wavelike muscular contractions of the foot
how do gastropods move?
attach the anterior sucker and pull the rest of the body forward
how to leeches crawl along solid objects?
mantle
in biology, a layer of tissue that covers the body of many invertebrates
clitellum
in many leeches and earthworms, a thick depression of the body wall that protects the eggs
mother of pearl
innermost layer of bivalve shell, iridescent, protects visceral mass from abrasion
foot
large, muscular organ used for locomotion
Gastropoda
largest, most diverse group of mollusks
perismatic
middle layer of bivalve shell, composed of calcium carbonate (calcite); thick provides strength
earthworm
most common member of class Oligochaeta
Hermaphroditic
most terrestrial and aquatic gastropods are _____.
parapodium
one of the appendages that are used for locomotion or gas exchange in annelids
seta
one of the external bristles or spines that project from the body of an annelid
chambered nautilus
only existing cephalopod that retained its external shell; shell is coiled and divided into a series of gas-filled chambers separated by partitions; soft body is confined to the outermost chamber; as it grows, moves forward in shell, makes new partition, fills chamber behind with gas -- makes nautilus buoyant
periostracum
outermost layer of a bivalve's shell, which helps reduce abrasions and protects it from the acidity of the water
chiton
polyplacophora example
Hirudinea
smallest class of annelids; aka leeches; live in calm bodies of fresh water or moist vegetation on land; no setae or parapodia; suckers at each end of body that attach to surfaces
head
structure that contains the mouth and varitey of sensory structures
slugs
terrestrial gastropods that look like snails without shells; respire through lining of mantle cavity like land snails
aortic arch
the bend of the aorta between its ascending and descending portions
hemocoel
the blood-filled space or body cavity of some invertebrates
visceral mass
the central section of a mollusk's body that contains the mollusk's organs
hemolymph
the fluid that circulated through the body of an animal that has an open circulatory system
calcium carbonate
the mantle secretes one or more hard shells containing ____.
calcite
the middle layer of the bivalve shell is composed of
mantle cavity
the space between the mantle and body mass in mollusks
esophagus
tube that food passes through after being sucked in by the pharynx (earthworm)
Oligochaeta, Polychaeta, Hirudinea
what are the 3 classes of annelids?
A segmented coelom enables different parts of the body to contract or expand independently. Duplication of some of the organ systems in each segment provides a form of insurance against injury (if one segment becomes disabled, the others can still function)
what are the advantages of segmentation?
"many plates"
what does Polyplacophora mean?
"little rings"
what does annelida mean?
"two valves"
what does bivalvia mean?
"head-foot"
what does cephalopoda mean?
"stomach-foot"
what does gastropod mean?
"soft-bodied"
what does mollusca mean
"naked gill"
what does nudibranch mean?
secretions of mucus, thin cuticle, moist environment
what helps keep an earthworm's skin moist?
mouth, digestive system, foot
where are the three parts of the bivalve nervous system located?
mantle cavity of female
where does fertilization occur in octopuses?
specialized tentacle of male
where is sperm kept in octopuses?
oxygen and carbon dioxide diffuse directly through skin, which contains many small blood vessels; this exchange can only take place if the skin is moist
why do earthworms need a moist environment?