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?