Chapter 33
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Chapter 33. Invertebrates. Overview: Life Without a Backbone. Invertebrates are animals that lack a backbone They account for 95% of known animal species. LE 33-2. Cnidaria. Echinodermata. Chordata. Porifera. Other bilaterians (including Nematoda, Arthropoda, Mollusca, and Annelida).

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Chapter 33

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Chapter 33

Chapter 33

Invertebrates


Overview life without a backbone

Overview: Life Without a Backbone

  • Invertebrates are animals that lack a backbone

  • They account for 95% of known animal species


Le 33 2

LE 33-2

Cnidaria

Echinodermata

Chordata

Porifera

Other bilaterians (including

Nematoda, Arthropoda,

Mollusca, and Annelida)

Deuterostomia

Bilateria

Eumetazoa

Ancestral colonial

choanoflagellate


Le 33 3a

LE 33-3a

A jelly

A sponge

0.5 mm

250 µm

A placozoan (LM)

A kinorhynch (LM)

A rotifer (LM)

A marine flatworm

Ectoprocts

Phoronids


Le 33 3b

LE 33-3b

A ribbon worm

A brachiopod

5 mm

A ctenophore, or comb jelly

An acanthocephalan

An octopus

A marine annelid

50 µm

A priapulan

A loriciferan (LM)


Le 33 3c

LE 33-3c

A roundworm

A scorpion

(an arachid)

100 µm

100 µm

Tardigrades (colorized SEM)

A cycliophoran (colorized SEM)

An acorn worm

An onychophoran

A sea urchin

A tunicate


Concept 33 1 sponges are sessile and have a porous body and choanocytes

Concept 33.1: Sponges are sessile and have a porous body and choanocytes

  • Sponges, phylum Porifera, live in both fresh and marine waters

  • Sponges lack true tissues and organs


Chapter 33

  • Sponges are suspension feeders, capturing food particles suspended in the water that passes through their body


Le 33 4

LE 33-4

Food particles

in mucus

Flagellum

Choanocyte

Choanocytes

Collar

Osculum

Azure vase sponge

(Callyspongia plicifera)

Spongocoel

Phagocytosis of

food particles

Amoebocyte

Porocytes

Spicules

Epidermis

Water

flow

Amoebocyte

Mesohyl


Chapter 33

  • Choanocytes, flagellated collar cells, generate a water current through the sponge and ingest suspended food

  • Most sponges are hermaphrodites: Each individual functions as both male and female


Concept 33 2 cnidarians have radial symmetry a gastrovascular cavity and cnidocytes

Concept 33.2: Cnidarians have radial symmetry, a gastrovascular cavity, and cnidocytes

  • All animals except sponges belong to the clade Eumetazoa, animals with true tissues

  • Phylum Cnidaria is one of the oldest groups in this clade


Chapter 33

  • Cnidarians have diversified into a wide range of both sessile and floating forms including jellies, corals, and hydras

  • They exhibit a relatively simple diploblastic, radial body plan


Chapter 33

  • The basic body plan of a cnidarian is a sac with a central digestive compartment, the gastrovascular cavity

  • A single opening functions as mouth and anus

  • There are two variations on the body plan: the sessile polyp and floating medusa

Video: Hydra Eating Daphnia (time lapse)


Le 33 5

LE 33-5

Mouth/anus

Tentacle

Polyp

Medusa

Gastrovascular

cavity

Gastrodermis

Mesoglea

Body

stalk

Epidermis

Tentacle

Mouth/anus


Chapter 33

  • Cnidarians are carnivores that use tentacles to capture prey

  • The tentacles are armed with cnidocytes, unique cells that function in defense and capture of prey

Video: Hydra Budding

Video: Hydra Releasing Sperm


Le 33 6

LE 33-6

Prey

Tentacle

“Trigger”

Discharge

of thread

Nematocyst

Coiled thread

Cnidocyte


Chapter 33

  • Phylum Cnidaria is divided into four major classes:

    • Hydrozoa

    • Scyphozoa

    • Cubozoa

    • Anthozoa


Le 33 7

LE 33-7

Scyphozoans (jellies)

Cubozoan (sea wasp)

Anthozoan

(sea anemone)

Hydrozoans


Chapter 33

Video: Jelly Swimming

Video: Thimble Jellies

Video: Clownfish and Anemone

Video: Coral Reef


Hydrozoans

Hydrozoans

  • Most hydrozoans alternate between polyp and medusa forms


Le 33 8 3

LE 33-8–3

Reproductive

polyp

Feeding

polyp

Medusa

bud

MEIOSIS

Gonad

Medusa

Sperm

Egg

SEXUAL

REPRODUCTION

ASEXUAL

REPRODUCTION

(BUDDING)

Portion of

a colony

of polyps

FERTILIZATION

Zygote

Developing

polyp

Mature

polyp

Planula

(larva)

Key

Haploid (n)

1 mm

Diploid (2n)


Scyphozoans

Scyphozoans

  • In the class Scyphozoa, jellies (medusae) are the prevalent form of the life cycle


Cubozoans

Cubozoans

  • In the class Cubozoa, which includes box jellies and sea wasps, the medusa is box-shaped and has complex eyes


Anthozoans

Anthozoans

  • Class Anthozoa includes the corals and sea anemones, which occur only as polyps


Concept 33 3 most animals have bilateral symmetry

Concept 33.3: Most animals have bilateral symmetry

  • The vast majority of animal species belong to the clade Bilateria, which consists of animals with bilateral symmetry and triploblastic development


Flatworms

Flatworms

  • Members of phylum Platyhelminthes live in marine, freshwater, and damp terrestrial habitats

  • They are flattened dorsoventrally and have a gastrovascular cavity

  • Although flatworms undergo triploblastic development, they are acoelomates


Chapter 33

  • Flatworms are divided into four classes:

    • Turbellaria (mostly free-living flatworms)

    • Monogenea (monogeneans)

    • Trematoda (trematodes, or flukes)

    • Cestoda (tapworms)


Turbellarians

Turbellarians

  • Turbellarians are nearly all free-living and mostly marine

  • The best-known turbellarians are commonly called planarians


Chapter 33

  • Planarians have light-sensitive eyespots and centralized nerve nets

  • The planarian nervous system is more complex and centralized than the nerve nets of cnidarians


Le 33 10

LE 33-10

Pharynx

Gastrovascular

cavity

Eyespots

Ganglia

Ventral nerve cords


Monogeneans and trematodes

Monogeneans and Trematodes

  • Monogeneans and trematodes live as parasites in or on other animals

  • They parasitize a wide range of hosts

  • Trematodes that parasitize humans spend part of their lives in snail hosts


Le 33 11

LE 33-11

Mature flukes live in the blood vessels

of the human intestine

Male

Female

1 mm

Larvae penetrate skin and blood vessels of humans.

Blood flukes reproduce sexually in the human host. Fertilized eggs exit host in feces.

Eggs develop in water into ciliated larvae. Larvae infect snails.

Asexual reproduction within snail results in another type of motile larva.

Snail host


Chapter 33

  • Most monogeneans are parasites of fish


Tapeworms

Tapeworms

  • Tapeworms are also parasitic and lack a digestive system


Le 33 12

LE 33-12

Proglottids with

reproductive structures

200 µm

Scolex

Hooks

Sucker


Rotifers

Rotifers

  • Rotifers, phylum Rotifera, are tiny animals that inhabit fresh water, the ocean, and damp soil

  • Rotifers are smaller than many protists but are truly multicellular and have specialized organ systems

Video: Rotifer


Le 33 13

LE 33-13

0.1 mm


Chapter 33

  • Rotifers have an alimentary canal: a digestive tube with a separate mouth and anus that lies within a fluid-filled pseudocoelom

  • Rotifers reproduce by parthenogenesis, in which females produce offspring from unfertilized eggs


Lophophorates ectoprocts phoronids and brachiopods

Lophophorates: Ectoprocts, Phoronids, and Brachiopods

  • Lophophorates have a lophophore, a horseshoe-shaped, suspension-feeding organ with ciliated tentacles


Chapter 33

  • Ectoprocts are colonial animals that superficially resemble plants


Le 33 14

LE 33-14

Lophophore

Lophophore

Ectoprocts

Phoronids

Brachiopods


Chapter 33

  • Phoronids are tube-dwelling marine worms ranging from 1 mm to 50 cm in length


Chapter 33

  • Brachiopods superficially resemble clams and other hinge-shelled molluscs, but the two halves of the shell are dorsal and ventral rather than lateral, as in clams


Nemerteans

Nemerteans

  • Members of phylum Nemertea are commonly called proboscis worms or ribbon worms


Chapter 33

  • The nemerteans’ unique proboscis is used for defense and prey capture and is extended by a fluid-filled sac

  • Nemerteans also have a closed circulatory system, in which the blood is contained in vessels distinct from fluid in the body cavity


Concept 33 4 molluscs have a muscular foot a visceral mass and a mantle

Concept 33.4: Molluscs have a muscular foot, a visceral mass, and a mantle

  • Phylum Mollusca includes snails and slugs, oysters and clams, and octopuses and squids

  • Most molluscs are marine, though some inhabit fresh water and some are terrestrial

  • Molluscs are soft-bodied animals, but most are protected by a hard shell


Chapter 33

  • All molluscs have a similar body plan with three main parts:

    • Muscular foot

    • Visceral mass

    • Mantle


Le 33 16

LE 33-16

Visceral mass

Coelom

Heart

Intestine

Nephridium

Gonads

Mantle

Stomach

Radula

Mantle

cavity

Shell

Mouth

Radula

Anus

Gill

Mouth

Nerve

cords

Foot

Esophagus


Chapter 33

  • Most molluscs have separate sexes with gonads located in the visceral mass

  • The life cycle of many molluscs includes a ciliated larval stage called a trochophore


Chapter 33

  • There are four major classes of molluscs:

    • Polyplacophora (chitons)

    • Gastropoda (snails and slugs)

    • Bivalvia (clams, oysters, and other bivalves)

    • Cephalopoda (squids, octopuses, cuttlefish, and chambered nautiluses)


Chitons

Chitons

  • Class Polyplacophora consists of the chitons, oval-shaped marine animals encased in an armor of eight dorsal plates


Gastropods

Gastropods

  • About three-quarters of all living species of molluscs belong to class Gastropoda

Video: Nudibranchs


Le 33 18

LE 33-18

A land snail

A sea slug. Nudibranchs, or sea slugs,

lost their shell during their evolution.


Chapter 33

  • Most gastropods are marine, but many are freshwater and terrestrial species

  • Most have a single, spiraled shell

  • Slugs lack a shell or have a reduced shell

  • The most distinctive characteristic of gastropods is torsion, which causes the animal’s anus and mantle to end up above its head


Le 33 19

LE 33-19

Stomach

Intestine

Mantle

cavity

Anus

Mouth


Bivalves

Bivalves

  • Molluscs of class Bivalvia include many species of clams, oysters, mussels, and scallops

  • They have a shell divided into two halves


Chapter 33

  • The mantle cavity of a bivalve contains gills that are used for feeding as well as gas exchange


Le 33 21

LE 33-21

Coelom

Hinge area

Mantle

Gut

Heart

Adductor

muscle

Shell

Anus

Mouth

Excurrent

siphon

Palp

Water

flow

Foot

Incurrent

siphon

Mantle

cavity

Gill


Cephalopods

Cephalopods

  • Class Cephalopoda includes squids and octopuses, carnivores with beak-like jaws surrounded by tentacles of their modified foot


Chapter 33

  • Most octopuses creep along the sea floor in search of prey


Le 33 22a

LE 33-22a

Octopuses are considered among the most intelligent invertebrates.


Chapter 33

  • Squids use their siphon to fire a jet of water, which allows them to swim very quickly


Le 33 22b

LE 33-22b

Squids are speedy carnivores with beaklike jaws and well-developed eyes.


Chapter 33

  • One small group of shelled cephalopods, the nautiluses, survives today


Le 33 22c

LE 33-22c

Chambered nautiluses are the only living cephalopods with an external shell.


Concept 33 5 annelids are segmented worms

Concept 33.5: Annelids are segmented worms

  • Annelids have bodies composed of a series of fused rings

  • The phylum Annelida is divided into three classes:

    • Oligochaeta (earthworms and their relatives)

    • Polychaeta (polychaetes)

    • Hirudinea (leeches)


Oligochaetes

Oligochaetes

  • Oligochaetes (class Oligochaeta) are named for relatively sparse chaetae, bristles made of chitin

  • They include the earthworms and a variety of aquatic species

  • Earthworms eat through soil, extracting nutrients as the soil moves through the alimentary canal

Video: Earthworm Locomotion


Le 33 23

LE 33-23

Cuticle

Coelom

Epidermis

Septum (partition

between segments)

Circular muscle

Longitudinal muscle

Metanephridium

Anus

Dorsal vessel

Chaetae

Intestine

Ventral vessel

Nerve

cords

Nephrostome

Metanephridium

Clitellum

Esophagus

Crop

Pharynx

Intestine

Giant Australian earthworm

Cerebral ganglia

Gizzard

Mouth

Ventral nerve cords

with segmental

ganglia

Subpharyngeal

ganglion

Circulatory

system


Polychaetes

Polychaetes

  • Members of class Polychaetes have paddlelike parapodia that work as gills and aid in locomotion

Video: Tubeworms


Le 33 24

LE 33-24

Parapodia


Leeches

Leeches

  • Members of class Hirudinea are blood-sucking parasites, such as leeches


Concept 33 6 nematodes are nonsegmented pseudocoelomates covered by a tough cuticle

Concept 33.6: Nematodes are nonsegmented pseudocoelomates covered by a tough cuticle

  • Nematodes, or roundworms, are found in most aquatic habitats, in the soil, in moist tissues of plants, and in body fluids and tissues of animals

  • The cylindrical bodies of nematodes (phylum Nematoda) are covered by a tough coat called a cuticle

Video: C. elegans Crawling

Video: C. elegans Embryo Development (time lapse)


Le 33 26

LE 33-26

25 µm


Chapter 33

  • Some species of nematodes are important parasites of plants and animals


Le 33 27

LE 33-27

Muscle tissue

Encysted juveniles

50 µm


Concept 33 7 arthropods are segmented coelomates that have an exoskeleton and jointed appendages

Concept 33.7: Arthropods are segmented coelomates that have an exoskeleton and jointed appendages

  • Two out of every three known species of animals are arthropods

  • Members of the phylum Arthropoda are found in nearly all habitats of the biosphere


General characteristics of arthropods

General Characteristics of Arthropods

  • The diversity and success of arthropods are largely related to their segmentation, hard exoskeleton, and jointed appendages


Chapter 33

  • Early arthropods, such as trilobites, showed little variation from segment to segment


Chapter 33

  • As arthropods evolved, the segments fused, and the appendages became more specialized

  • The appendages of some living arthropods are modified for many different functions

Video: Lobster Mouth Parts


Le 33 29

LE 33-29

Cephalothorax

Abdomen

Thorax

Head

Antennae

(sensory

reception)

Swimming

appendages

(two sets

located under

abdomen

Walking legs

Pincer (defense)

Mouthparts (feeding)


Chapter 33

  • The body of an arthropod is completely covered by the cuticle, an exoskeleton made of chitin

  • When an arthropod grow, it molts its exoskeleton in a process called ecdysis


Chapter 33

  • Arthropods have an open circulatory system in which fluid called hemolymph is circulated into the spaces surrounding the tissues and organs

  • A variety of organs specialized for gas exchange have evolved in arthropods


Chapter 33

  • Molecular evidence suggests that living arthropods consist of four major lineages that diverged early in the phylum’s evolution:

    • Cheliceriforms (sea spiders, horseshoe crabs, scorpions, ticks, mites, and spiders)

    • Myriapods (centipedes and millipedes)

    • Hexapods (insects and relatives)

    • Crustaceans (crabs, lobsters, shrimps, barnacles, and many others)


Cheliceriforms

Cheliceriforms

  • Cheliceriforms, subphylum Cheliceriformes, are named for clawlike feeding appendages called chelicerae

  • Most marine cheliceriforms are extinct, but some species survive today, including horseshoe crabs


Chapter 33

  • Most modern cheliceriforms are arachnids, which include spiders, scorpions, ticks, and mites


Le 33 31a

LE 33-31a

Scorpions have pedipalps that are pincers specialized for defense and the capture of food. The tip of the tail bears a poisonous stinger.


Le 33 31b

LE 33-31b

50 µm

Dust mites are ubiquitous scavengers in human dwellings but are harmless except to those people who are allergic to them (colorized SEM).


Le 33 31c

LE 33-31c

Web-building spiders are generally most active during the daytime.


Chapter 33

  • Arachnids have an abdomen and a cephalothorax, which has six pairs of appendages, the most anterior of which are the chelicerae


Le 33 32

LE 33-32

Stomach

Intestine

Brain

Heart

Digestive

gland

Eyes

Ovary

Poison

gland

Anus

Book lung

Gonopore

(exit for eggs)

Spinnerets

Pedipalp

Chelicera

Sperm

receptacle

Silk gland


Myriapods

Myriapods

  • Subphylum Myriapoda includes millipedes and centipedes

  • Millipedes, class Diplopoda, have many legs

  • Each trunk segment has two pairs of legs


Chapter 33

  • Centipedes, class Chilopoda, are carnivores with jaw-like mandibles

  • They have one pair of legs per trunk segment


Insects

Insects

  • Subphylum Hexapoda, insects and relatives, has more species than all other forms of life combined

  • They live in almost every terrestrial habitat and in fresh water

  • The internal anatomy of an insect includes several complex organ systems


Le 33 35

LE 33-35

Thorax

Abdomen

Head

Compound eye

Antennae

Dorsal

artery

Crop

Cerebral ganglion

Heart

Anus

Vagina

Malpighian tubules

Ovary

Tracheal tubes

Mouthparts

Nerve cords


Chapter 33

  • Flight is one key to the great success of insects

  • An animal that can fly can escape predators, find food, and disperse to new habitats much faster than organisms that can only crawl


Chapter 33

  • Many insects undergo metamorphosis during their development

  • In incomplete metamorphosis, the young, called nymphs, resemble adults but are smaller and go through a series of molts until they reach full size


Chapter 33

  • Insects with complete metamorphosis have larval stages known by such names as maggot, grub, or caterpillar

  • The larval stage looks entirely different from the adult stage

Video: Butterfly Emerging


Le 33 36

LE 33-36

Larva (caterpillar)

Pupa

Pupa

Emerging adult

Adult


Chapter 33

  • Insects are classified into about 26 orders

Video: Bee Pollinating


Le 33 37aa

LE 33-37aA

APPROXIMATE

NUMBER OF

SPECIES

MAIN CHARACTERISTICS

EXAMPLES

ORDER

Blattodea

4,000

Cockroaches have a dorsoventrally flattened body, with legs modified for rapid running. Forewings, when present, are leathery, whereas hind wings are fanlike. Fewer than 40 cockroach species live in houses; the rest exploit habitats ranging from tropical forest floors to caves and deserts.

German

cockroach


Le 33 37ba

LE 33-37bA

APPROXIMATE

NUMBER OF

SPECIES

MAIN CHARACTERISTICS

EXAMPLES

ORDER

Beetles comprise the most species-rich order of insects. They have two pairs of wings, one of which is thick and leathery, the other membranous. They have an armored exoskeleton and mouthparts adapted for biting and chewing. Beetles undergo complete metamorphosis.

Coleoptera

350,000

Japanese

beetle


Le 33 37ca

LE 33-37cA

APPROXIMATE

NUMBER OF

SPECIES

MAIN CHARACTERISTICS

EXAMPLES

ORDER

Earwigs are generally nocturnal scavengers. While some species are wingless, others have two pairs of wings, one of which is thick and leathery, the other membranous. Earwigs have biting mouthparts and large posterior pincers. They undergo incomplete metamorphosis.

Dermaptera

1,200

Earwig


Le 33 37da

LE 33-37dA

APPROXIMATE

NUMBER OF

SPECIES

MAIN CHARACTERISTICS

EXAMPLES

ORDER

Dipterans have one pair of wings; the second pair has become modified into balancing organs called halteres. Their head is large and mobile; their mouthparts are adapted for sucking, piercing, or lapping. Dipterans undergo complete metamorphosis. Flies and mosquitoes are among the best-known dipterans, which live as scavengers, predetors, and parasites.

Diptera

151,000

Horsefly


Le 33 37ea

LE 33-37eA

APPROXIMATE

NUMBER OF

SPECIES

MAIN CHARACTERISTICS

EXAMPLES

ORDER

Hemipterans are so-called “true bugs,” including bed bugs, assassin bugs, and chinch bugs. (Insects in other orders are sometimes erroneously called bugs.) Hemipterans have two pairs of wings, one pair partly leathery, the other membranous. They have piercing or sucking mouthparts and undergo incomplete metamorphosis.

Hemiptera

85,000

Leaf-

footed

bug


Le 33 37fa

LE 33-37fA

APPROXIMATE

NUMBER OF

SPECIES

MAIN CHARACTERISTICS

EXAMPLES

ORDER

Hymenoptera

Ants, bees, and wasps are generally highly social insects. They have two pairs of membranous wings, a mobile head, and chewing or sucking mouthparts. The females of many species have a posterior stinging organ. Hymenopterans undergo complete metamorphosis.

125,000

Cicada-killer wasp


Le 33 37ga

LE 33-37gA

APPROXIMATE

NUMBER OF

SPECIES

MAIN CHARACTERISTICS

EXAMPLES

ORDER

2,000

Termites are widespread social insects that produce enormous colonies. It had been estimated that there are 700 kg of termites for every person on Earth! Some termites have two pairs of membranous wings, while others are wingless. They feed on wood with the aid of microbial symbionts carried in specialized chambers in their hindgut.

Isoptera

Termite


Le 33 37ab

LE 33-37aB

APPROXIMATE

NUMBER OF

SPECIES

MAIN CHARACTERISTICS

EXAMPLES

ORDER

Butterflies and moths are among the best-known insects. They have two pairs of wings covered with tiny scales. To feed, they uncoil a long proboscis. Most feed on nectar, but some species feed on other substances, including animal blood or tears.

Lepidoptera

120,000

Swallowtail

butterfly


Le 33 37bb

LE 33-37bB

APPROXIMATE

NUMBER OF

SPECIES

MAIN CHARACTERISTICS

EXAMPLES

ORDER

Dragonflies and damselflies have two pairs of large, membranous wings. They have an elongated abdomen, large, compound eyes, and chewing mouthparts. They undergo incomplete metamorphosis and are active predators.

Odonata

5,000

Dragonfly


Le 33 37cb

LE 33-37cB

APPROXIMATE

NUMBER OF

SPECIES

MAIN CHARACTERISTICS

ORDER

EXAMPLES

Grasshoppers, crickets, and their relatives are mostly herbivorous. They have large hind legs adapted for jumping, two pairs of wings (one leathery, one membranous), and biting or chewing mouthparts. Males commonly make courtship sounds by rubbing together body parts, such as a ridge of their hind leg. Orthopterans undergo incomplete metamorphosis.

Orthoptera

13,000

Katydid


Le 33 37db

LE 33-37dB

APPROXIMATE

NUMBER OF

SPECIES

MAIN CHARACTERISTICS

EXAMPLES

ORDER

Stick insects and leaf insects are exquisite mimics of plants. The eggs of some species even mimic seeds of the plants on which the insects live. Their body is cylindrical or flattened dorsoventrally. They lack forewings but have fanlike hind wings. Their mouthparts are adapted for biting or chewing.

Phasmida

2,600

Stick insect


Le 33 37eb

LE 33-37eB

APPROXIMATE

NUMBER OF

SPECIES

MAIN CHARACTERISTICS

EXAMPLES

ORDER

Phthiraptera

Commonly called sucking lice, these insects spend their entire life as an ectoparasite feeding on the hair or feathers of a single host. Their legs, equipped with clawlike tarsi, are adapted for clinging to their hosts. They lack wings and have reduced eyes. Sucking lice undergo incomplete metamorphosis.

2,400

Human

body

louse


Le 33 37fb

LE 33-37fB

APPROXIMATE

NUMBER OF

SPECIES

MAIN CHARACTERISTICS

EXAMPLES

ORDER

Fleas are bloodsucking ectoparasites on birds and mammals. Their body is wingless and laterally compressed. Their legs are modified for clinging to their hosts and for long-distance jumping. They undergo complete metamorphosis.

Siphonaptera

2,400

Flea


Le 33 37gb

LE 33-37gB

APPROXIMATE

NUMBER OF

SPECIES

MAIN CHARACTERISTICS

EXAMPLES

ORDER

Silverfish are small, wingless insects with a flattened body and reduced eyes. They live in leaf litter or under bark. They can also infest buildings, where they can become pests.

Thysanura

450

Silverfish


Le 33 37hb

LE 33-37hB

APPROXIMATE

NUMBER OF

SPECIES

MAIN CHARACTERISTICS

EXAMPLES

ORDER

Trichoptera

The larvae of caddisflies live in streams, where they make houses from sand grains, wood fragments, or other material held together by silk, Adults have two pairs of hairy wings and chewing or lapping mouthparts. They undergo complete metamorphosis.

7,100

Caddisfly


Crustaceans

Crustaceans

  • While arachnids and insects thrive on land, crustaceans, for the most part, have remained in marine and freshwater environments

  • Crustaceans, subphylum Crustacea, typically have branched appendages that are extensively specialized for feeding and locomotion


Chapter 33

  • Decapods are all relatively large crustaceans and include lobsters, crabs, crayfish, and shrimp


Chapter 33

  • Planktonic crustaceans include many species of copepods, which are among the most numerous of all animals


Chapter 33

  • Barnacles are a group of mostly sessile crustaceans

  • They have a cuticle that is hardened into a shell


Concept 33 8 echinoderms and chordates are deuterostomes

Concept 33.8: Echinoderms and chordates are deuterostomes

  • Sea stars and other echinoderms, phylum Echinodermata, may seem to have little in common with phylum Chordata, which includes the vertebrates


Chapter 33

  • Chordates and echinoderms share characteristics of deuterostomes:

    • Radial cleavage

    • Development of the coelom from the archenteron

    • Formation of the mouth at the end of the embryo opposite the blastopore


Echinoderms

Echinoderms

  • Sea stars and most other echinoderms are slow-moving or sessile marine animals

  • A thin, bumpy or spiny skin covers an endoskeleton of hard calcareous plates

  • Unique to echinoderms is a water vascular system, a network of hydraulic canals branching into tube feet that function in locomotion, feeding, and gas exchange

Video: Echinoderm Tube Feet


Le 33 39

LE 33-39

Spine

Stomach

Anus

Gills

Central disk

Madreporite

Digestive glands

Radial

nerve

Ring

canal

Gonads

Ampulla

Podium

Radial canal

Tube

feet


Chapter 33

  • Radial anatomy of many echinoderms evolved from the bilateral symmetry of ancestors

  • Living echinoderms are divided into six classes:

    • Asteroidia (sea stars)

    • Ophiuroidea (brittle stars)

    • Echinoidea (sea urchins and sand dollars)

    • Crinoidea (sea lilies and feather stars)

    • Holothuroidea (sea cucumbers)

    • Concentricycloidea (sea daisies)


Sea stars

Sea Stars

  • Sea stars, class Asteroidea, have multiple arms radiating from a central disk

  • The undersurfaces of the arms bear tube feet, each of which can act like a suction disk


Le 33 40a

LE 33-40a

A sea star (class Asteroidea)


Brittle stars

Brittle Stars

  • Brittle stars have a distinct central disk and long, flexible arms


Le 33 40b

LE 33-40b

A brittle star (class Ophiuroidea)


Sea urchins and sand dollars

Sea Urchins and Sand Dollars

  • Sea urchins and sand dollars have no arms but have five rows of tube feet


Le 33 40c

LE 33-40c

A sea urchin (class Echinoidea)


Sea lilies and feather stars

Sea Lilies and Feather Stars

  • Sea lilies live attached to the substrate by a stalk

  • Feather stars crawl using long, flexible arms


Le 33 40d

LE 33-40d

A feather star (class Crinoidea)


Sea cucumbers

Sea Cucumbers

  • Sea cucumbers do not look much like other echinoderms

  • They lack spines, and their endoskeleton is much reduced


Le 33 40e

LE 33-40e

A sea cucumber (class Holothuroidea)


Sea daisies

Sea Daisies

  • Sea daisies were discovered in 1986, and only two species are known


Le 33 40f

LE 33-40f

A sea daisy (class Concentricycloidea)


Chordates

Chordates

  • Phylum Chordata consists of two subphyla of invertebrates as well as hagfishes and vertebrates

  • Chordates share many features of embryonic development with echinoderms


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