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Chapter 15 Key Terms
Zoology
Endoskeleton
Bilateral Symmetry
Invertebrate
Gastropod
Echinoderm
Nematocyst
Exoskeleton
Radial Symmetry
Vertebrate
Annelid
Cephalopod
Cnidarian
Planarian
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Biology Chapter 15
INVERTEBRATES
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Characteristics










Zoology – study of animals
Movement
Support – exoskeleton vs endoskeleton
Protective body covering
Nutrition – heterotrophic – ingestion, digestion, assimilation
Respiration
Circulation – transportation of materials throughout the animal
Excretion – elimination of wastes
Response – irritability: perceiving and responding to environment
Reproduction
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Animal Anatomy

Symmetry

Symmetrical
 Can
be cut into equal halves
 Spherical
 Radial
symmetry
 Bilateral

symmetry
symmetry
Asymmetrical
 Cannot
be divided into equal halves
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Anatomical Terms
 Cephalic
– toward the head
 Caudal – toward the tail
 Anterior – toward the front
 Posterior – toward the rear (farthest back)
 Dorsal – toward the back
 Ventral – toward the belly
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Anatomical Terms
 Lateral
– Toward the side
 Medial – toward the middle
 Midline – divides into right and left
 Transverse – crosses perpendicular to the midline
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Classification of Animals

Vertebrates
 Animals
that have a
backbone

Invertebrates
 Animals
that don’t
have a backbone

95% of animals are
invertebrates
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Phylum Porifera

“Pore bearers”
 Ex.

Sponges
Filter feeders
 Pull
water in through tiny ostia and expel it through the larger
osculum
 Collar
 Collar
cells generate a current that brings water in
cells engulf and partially digests food, then transfers it to
amoebocytes
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Phylum Cnidaria

All Cnidarians are aquatic that come in two basic forms

Polyp
 Cup-shaped
with mouth and tentacles at one end, and basal
disc for attachment at other end

Medusa
 Bell-shaped

body and swims freely
Many Cnidarians have both polyp and medusa stages during
their life cycles
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Class Hydrozoa

Hydras

Usually found in quiet lakes or ponds

One opening – mouth

Gastrovascular cavity – digestion and food circulation

Cnidocytes – stinging cells that line the tentacles

Nematocysts – capsules containing poisonous barbs
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Class Scyphozoa

Jellyfish

Go through both polyp and medusa stages

Has long, stinging tentacles

Cnidocyte (aka cnidoblast)

Same general structure as hydra
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Class Anthozoa

“Flower animals”

Corals
 Small
polyp that lives in self-made stone skeleton or cup
 Cement

themselves on each other, forming colony/reef
Sea Anemones
 Polyps
with a hydrostatic skeleton
 Tentacles
that shoot out nematocysts
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Great Barrier Reef

Off coast of Australia

Only living structure seen from space

1 of 7 natural wonders of the world

Made up of over 3000 individual reef systems

Coral polyps
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Worms
Soft-bodied, long, legless organisms (some have
appendages)
 All have cephalic region where most sensory organs and
nerve cells are concentrated (cephalization)
 Exhibit bilateral symmetry
 Bodies develop from 3 cell layers

 Epidermis
– outer layer; protection, locomotion
 Mesoderm – between other two layers; develops organs
 Gastroderm – inner layer; lines digestive tract
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Phylum Platyhelminthes

“Flatworms” – thin flat body

Free-living flatworms
 Planarians
 Inhabit
(Class Turbellaria)
freshwater lakes and streams
 Epidermis,
 Ventral
 Flame
mesoderm, gastroderm
mouth with pharynx
cells push wastes to excretory pores
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Planarians

Hermaphroditic
 Contain
both male and female reproductive organs
 Cross-fertilizes
 Both
with another planarian
release several fertilized eggs

Two longitudinal nerves extend from the brain down the length
of the planarian

Transverse nerves connect the longitudinal nerves, allowing it
to coordinate responses
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Phylum Platyhelminthes

Parasitic Flatworms

Thick tegument (protective body covering)

Structures used for attachment (hooks)

Class Trematoda (Flukes)
 Sheep
 Snail

liver fluke
is an intermediate host
Class Cestoda (Tapeworms)
 Scolex
and proglottids
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Sheep Liver FLuke
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Pork Tapeworm
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Phylum Nematoda

The roundworms

Ascaris
 Intestinal
roundworm
 Has
digestive canal with 2 openings
(mouth, anus)

Do not pose much threat to the host,
unless they become overpopulated
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Phylum Annelida

Literally means “little rings”

Divided into small segments

Thin membrane (septum) separates
each segment of the annelid’s body

Clitellum is used in reproduction
and is closer to the anterior end

Setae help move the worm along
with two muscle layers
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Phylum Annelida

Soil is drawn in by the pharynx

Soil is passed down hrough the
esophagus to the crop

Crop temporarily stores soil/food
until it is passed to the gizzard

Gizzard grinds food into smaller
pieces and passed to intestine

Intestine digests the food and is
absorbed into the blood
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Phylum Annelida
Closed circulatory system
 Dorsal blood vessel – anterior
 Ventral blood vessel – posterior
 Aortic arches connect dorsal and
ventral blood vessels

 Help
regulate blood pressure
Cuticle on worm’s skin must be
kept moist to allow gas exchange
 Nephridia – filter and expel wastes

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Phylum Mollusca

Characteristics

Mantle: encloses organs, secretes shell

Shell: tough structure secreted by mantle that protects animal

Visceral mass: part that contains heart, digestive and
excretory organs, usually covered by mantle

Foot: muscular organ used for locomotion

Radula: small organ that scrapes up food and draws it into its
mouth
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Class Bivalvia

“2 shells”

Clams, oysters, mussels

Shell (valve) is secreted by the mantle

Muscular foot used in locomotion

Contain two siphons that filter food out of water as it circulates
through body
 Incurrent

and excurrent
Open circulatory system
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Class Gastropoda

Snails, slugs

Snail is a univalve (one shell)

Can reach speeds of 3 m per hour!
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Class Cephalopoda

Squid, Octopus, Cuttlefish

Octopus

Move by siphons and tentacles

Suction disks on tentacles

Protection
 Ink
jets
 Pigments
to help camouflage
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Phylum Echinodermata

Characteristics
 Radial
symmetry
 Skeleton
is made up of plates called ossicles
 Water-vascular

system – used for locomotion and food capture
Ex. Starfish (Class Asteroidia)
5
rays situated around a central disc
 Able
to regenerate if the ray has a portion of the central disc
 Everts
its stomach into the shells of mollusks
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Phylum Echinodermata

Sea Urchins and Sand Dollars (Class Echinoidea)

Sea Cucumbers (Class Holothuroidea)

Brittle Stars (Class Ophiuroidea)

Sea Lilies and Feather Stars (Class Crinoidea)