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Chapter 33
Invertebrates
Let’s meet the … Invertebrates
Life Without a Backbone
InvertebratesAre animals that lack a backboneAccount for 95% of known animal species
Xmas Tree Worm
A review of animal phylogeny
Ancestral colonialchoanoflagellate
Eumetazoa
Bilateria
Deuterostomia
Po
rife
ra
Cn
ida
ria
Oth
er
bila
teria
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(incl
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ing
Ne
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ollu
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Ch
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Invertebrate diversity
PORIFERA (5,500 species)
A sponge
CNIDARIA (10,000 species)
A jelly
PLACOZOA (1 species) KINORHYNCHA (150 species)0.5 mm
A placozoan (LM) A kinorhynch (LM)250 µm
PLATYHELMINTHES (20,000 species) ROTIFERA (1,800 species)
A marine flatworm A rotifer (LM)
ECTOPROCTA (4,500 species) PHORONIDA (20 species)
Ectoprocts Phoronids
BRACHIOPODA (335 species) NEMERTEA (900 species)
A brachiopod A ribbon wormACANTHOCEPHALA (1,100 species) CTENOPHORA (100 species)
An acanthocephalan A ctenophore, or comb jelly
MOLLUSCA (93,000 species) ANNELIDA (16,500 species)
An octopus A marine annelidLORICIFERA (10 species) PRIAPULA (16 species)
5 mm
50 µm
A loriciferan (LM) A priapulan
Invertebrate Diversity
Invertebrate DiversityNEMATODA (25,000 species) ARTHROPODA (1,000,000 + species)
A roundworm A scorpion (an arachnid)
CYCLIOPHORA (1 species) TARDIGRADA (800 species)100 µm
100 µm
A cycliophoran (colorized SEM) Tardigrades (colorized SEM)
ONYCHOPHORA (110 species) HEMICHORDATA (85 species)
An onychophoran An acorn worm
ECHINODERMATA (7,000 species) CHORDATA (52,000 species)
A sea urchin A tunicate
Sponges (Phylum Porifera)
Sponge characteristics Sessile Porous body Choanocytes: flagellated collar cells generate a water current
through the sponge and ingest suspended food by phagocytosis Live in both fresh and marine waters Lack true tissues (groups of similar cells that form a functional unit). All
animals except sponges belong to the clade Eumetazoa, the animals with true tissues
Most sponges are hermaphrodites (each individual functions as both male and female)
Sponges Sponges are suspension feeders
Capturing food particles suspended in the water that passes through their body
Azure vase sponge (Callyspongia plicifera)
Osculum
Spicules
Waterflow
Flagellum
CollarFood particlesin mucus
Choanocyte
Phagocytosis offood particles Amoebocyte
Choanocytes. The spongocoel is lined with feeding cells called choanocytes. By beating flagella, the choanocytes create a current that draws water in through the porocytes.
Spongocoel. Water passing through porocytes
enters a cavity called the spongocoel.
Porocytes. Water enters the epidermis through
channels formed by porocytes, doughnut-shaped cells that span the body wall.
Epidermis. The outer layer consists of tightly
packed epidermal cells.
Mesohyl. The wall of this simple sponge consists of
two layers of cells separatedby a gelatinous matrix, themesohyl (“middle matter”).
The movement of the choanocyte flagella also draws water through its collar of fingerlike projections. Food particles are trapped in the mucus coating the projections, engulfed by phagocytosis, and either digested or transferred to amoebocytes.
Amoebocyte. Amoebocytes transport nutrients to other cells ofthe sponge body and also produce materials for skeletal fibers (spicules).
5
6
7
4
3
2
1
Cnidarians (Phylum Cnidaria)
A diverse range of both sessile and floating organisms including hydras, jellies, sea anemones, and corals
Cnidarian characteristics radial symmetry gastrovascular cavity
(digestive compartment) Cnidocytes movie
Cnidarian Body Plan Relatively simple diploblastic (two germ layers), radial body plan Basic body plan of a cnidarian is a sac with a central digestive compartment, the
gastrovascular cavity A single opening functions as both mouth and anus There are two variations on this body plan
The sessile polyp and the floating medusa
Mouth/anus
TentacleGastrovascularcavity
Gastrodermis
Mesoglea
Epidermis
Tentacle
Bodystalk
Mouth/anus
MedusaPolyp
Tentacle
“Trigger”
Nematocyst
Coiled thread
DischargeOf thread
Cnidocyte
Prey
Cnidarian Feeding Cnidarians are carnivores
That use tentacles to capture prey The tentacles are armed with cnidocytes
Unique cells that function in defense and the capture of prey
Threads can inject poison into the prey, or stick to or entangle the target
Classes of Phylum Cnidaria
Hydrozoan Life Cycle
Feeding polyp
Reproductivepolyp
Medusabud
ASEXUALREPRODUCTION(BUDDING)
GonadMedusa
MEIOSIS
FERTILIZATION
SEXUALREPRODUCTION Egg Sperm
Developingpolyp
Portion ofa colonyof polyps
Maturepolyp
Planula(larva) Key
Haploid (n)Diploid (2n)1 mm
Zygote
A colony ofinterconnected
polyps (inset,LM) results
from asexualreproductionby budding.
1
Some of the colony’s polyps, equipped with tentacles, are specialized for feeding.
2 Other polyps, specialized for reproduction, lack tentacles and produce tiny medusae by asexual budding.
3
The medusae swim off, grow, and reproduce sexually.
4
The zygote develops into a solid ciliated larva called a planula.5 The planula eventually settles
and develops into a new polyp.6
Classes: Hydrozoa, Scyphozoa, Cubozoa, and Anthozoa
(a) These colonial polyps are members of
class Hydrozoa.
(b) Many species of jellies (class
Scyphozoa), including thespecies pictured here, are bioluminescent. The largest scyphozoans have tentaclesmore than 100 m long dangling from a bell-shaped body up to 2 m in diameter.
(c) The sea wasp (Chironex fleckeri) is a member of
class Cubozoa. Its poison,which can subdue fish andother large prey, is more potent than cobra venom.
(d) Sea anemones and other
members of class Anthozoaexist only as polyps.
Cnidarian Classes In the class Hydrozoa
Most hydrozoans alternate between polyp and medusa forms. Freshwater Hydras exist only in the polyp form.
In the class Scyphozoa Jellies (medusae) are the prevalent form of the life cycle
In the class Cubozoa, which includes box jellies and sea wasps The medusa is box-shaped and has complex eyes
Class Anthozoa includes the corals and sea anemones Which occur only as polyps Hydra
Purple coral
Hydra movie 1
Hydra movie 2
Coral reproduction
Jellyfish movie
Bilateria
Most animals have bilateral symmetry The vast majority of animal species belong
to the clade BilateriaWhich consists of animals with bilateral
symmetry and triploblastic development
Flatworms
Members of phylum PlatyhelminthesLive in marine, freshwater, and damp terrestrial
habitats. Some are parasitic.Are flattened dorsoventrally and have bilateral
symmetryUndergo triploblastic developmentAre acoelomates (lack a coelom) with gastrovascular
cavities.Lack a digestive system entirely and absorb
nutrients across their body surface.
Flatworm Classes
Turbellarians Are nearly all free-living and mostly marine
Turbellarians Planarians are common examples of
turbellarians They have light-sensitive eyespots and centralized
nerve nets
Pharynx. The mouth is at thetip of a muscular pharynx thatextends from the animal’sventral side. Digestive juicesare spilled onto prey, and thepharynx sucks small pieces offood into the gastrovascularcavity, where digestion continues.
Digestion is completed withinthe cells lining the gastro-vascular cavity, which hasthree branches, each withfine subbranches that pro-vide an extensive surface area.
Undigested wastesare egestedthrough the mouth.
Ganglia. Located at the anterior endof the worm, near the main sourcesof sensory input, is a pair of ganglia,dense clusters of nerve cells.
Ventral nerve cords. Fromthe ganglia, a pair ofventral nerve cords runsthe length of the body.
Gastrovascularcavity
Eyespots
Monogeneans and Trematodes Live as parasites in or on
other animals They parasitize a wide range of hosts
Most monogeneans are parasites of fish
Trematodes (Flukes) that parasitize humans spend part of their lives in snail hosts
These larvae penetratethe skin and blood vessels of humans working in irrigated fields contaminated with infected human feces.
Asexual reproduction within a snail results in another type of motilelarva, which escapes from the snail host.
Blood flukes reproduce sexually in the human host. The fertilized eggs exit the host in feces.
The eggs develop in water into ciliated larvae. These larvaeinfect snails, the intermediate hosts.
Snail host
1 mm
Female
Male
5
2
3
4
Mature flukes live in the blood vessels of the human intestine. A female fluke fits into a groove running the length of the larger male’s body, as shown in the light micrograph at right.
1
Tapeworms (Class Cestoda)Are also parasitic and lack a digestive system
Proglottids withreproductive structures
200 µm
HooksSucker
Scolex
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 Rotifers have an alimentary canal
A digestive tube with a separate mouth and anus that lies within a fluid-filled pseudocoelom Some species of rotifers reproduce by parthenogenesis
In which females produce more females from unfertilized eggs
0.1 mm
Rotifers (Phylum Rotifera)
Rotifer movie 2
Three Phyla of Lophophorates: Ectoprocts, Phoronids, and Brachiopods
Lophophorates have a lophophoreA horseshoe-shaped, suspension-feeding
organ bearing ciliated tentacles that trap suspended food particles
EctoproctsAre colonial animals that superficially resemble
plantsLophophore
Ectoprocts, such as this sea mat (Membraniporamembranacea), are colonial lophophorates.
(a)
Phoronids
Are tube-dwelling marine worms ranging from 1 mm to 50 cm in length
Lophophore
In phoronids such as Phoronis hippocrepia, the lophophore and mouth are at one end of an elongated trunk.
(b)
Brachipods 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
Lophophore
Brachiopods have a hinged shell. The two parts of the shell are dorsal and ventral.
(c)
Nemerteans (Phylum Nemertea) Commonly called proboscis worms or ribbon worms The nemerteans unique proboscis
Is used for defense and prey capture 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
Molluscs (Phylum Mollusca)
Phylum Mollusca: Includes snails and slugs, oysters and clams, and octopuses and squids
Mollusc characteristics Body plan: muscular foot, visceral mass, and a mantle Mantle is a fold of tissue that drapes over the visceral mass and
secretes the shell. 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 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
Mollusc anatomy
Visceral mass
Mantle
Foot
Coelom Intestine
Gonads
Mantlecavity
Anus
Gill
Nervecords Esophagus
Stomach
ShellRadula
Mouth
Mouth
Nephridium. Excretory organs called nephridia remove metabolic wastes from the hemolymph.
Heart. Most molluscs have an open circulatory system. The dorsally located heart pumps circulatory fluid called hemolymph through arteries into sinuses (body spaces). The organs of the mollusc are thus continually bathed in hemolymph.
The long digestive tract is coiled in the visceral mass.
Radula. The mouth region in many mollusc species contains a rasp-like feeding organ called a radula. This belt of backward-curved teeth slides back and forth, scraping and scooping like a backhoe.
The nervous system consists
of a nerve ring around the
esophagus, from which nerve
cords extend.
Classes of molluscs
Chitons Class Polyplacophora is composed of the
chitons (Oval-shaped marine animals encased in an armor of eight dorsal plates)
Gastropods
About three-quarters of all living species of molluscs belong to class Gastropoda
A land snail (a)
A sea slug. Nudibranchs, or sea slugs, lost their shell during their evolution.
(b)
Gastropods Gastropod characteristics
Most are marine, but there are also many freshwater and terrestrial species
Possess a single, spiraled shell Slugs lack a shell or have a
reduced shell The most distinctive characteristic
of this class is a developmental process known as torsion, which causes the animal’s anus and mantle to end up above its head
Anus
Mantlecavity
StomachIntestine
Mouth
Bivalves (Molluscs of class Bivalvia) Include many species of clams, oysters,
mussels, and scallopsHave a shell divided into two halves
Bivalves The mantle cavity of a bivalve contains gills that
are used for feeding as well as gas exchange
Hinge areaGut Coelom
Heart
Adductormuscle
AnusExcurrentsiphon
Waterflow
IncurrentsiphonGill
Mantlecavity
Foot
Palp
Mouth
Shell
Mantle
Clam locomotion
Cephalopods
Class Cephalopoda includes squids and octopusesCarnivores with beak-like jaws surrounded by
tentacles of their modified foot
Octopus Most octopuses creep along the sea floor in
search of prey
(a) Octopuses are considered among the most intelligent invertebrates.
Squid Squids use their siphon to fire a jet of water,
which allows them to swim very quickly
(b) Squids are speedy carnivores with beaklike jaws and well-developed eyes.
` One small group of shelled cephalopodsThe nautiluses, survives today
(c) Chambered nautiluses are the only living cephalopods with an external shell.
Annelids
AnnelidsSegmented wormsHave bodies composed of a series of fused
rings3 Classes Oligochaeta, Polychaeta, Hirudinea
Classes of Annelida
Oligochaetes
Oligochaetes (class Oligochaeta) Are named for their relatively sparse chaetae (bristles made of
chitin) Include the earthworms and a variety of aquatic species
Earthworms eat their way through the soil, extracting nutrients as the soil moves through the alimentary canal Which helps till the earth, making earthworms valuable to
farmers
MouthSubpharyngealganglion
Pharynx EsophagusCrop
Gizzard
Intestine
Metanephridium
Ventralvessel
Nervecords
Nephrostome
Intestine
Dorsalvessel
Longitudinalmuscle
Circularmuscle
Epidermis Cuticle
Septum(partitionbetweensegments)
Anus
Each segment is surrounded by longitudinal muscle, which in turn is surrounded by circular muscle. Earthworms coordinate the contraction of these two sets of muscles to move (see Figure 49.25). These muscles work against the noncompressible coelomic fluid, which acts as a hydrostatic skeleton.
Coelom. The coelom of the earthworm is partitioned by septa.
Metanephridium. Each segment of the worm contains a pair of excretory tubes, called metanephridia, with ciliated funnels, called nephrostomes. The metanephridia remove wastes from the blood and coelomic fluid through exterior pores.
Tiny blood vessels are abundant in the earthworm’s skin, which functions as its respiratory organ. The blood contains oxygen-carryinghemoglobin.
Ventral nerve cords with segmental ganglia. The nerve cords penetrate the septa and run the length of the animal, as do the digestive tract and longitudinal blood vessels.
The circulatory system, a network of vessels, is closed. The dorsal and ventral vessels are linked by segmental pairs of vessels. The dorsal vessel and five pairs of vessels that circle the esophagus of an earthworm are muscular and pump blood through the circulatory system.
Cerebral ganglia. The earthworm nervous system features a brain-like pair of cerebral ganglia above and
in front of the pharynx. A ring of nerves around the pharynx connects to a subpharyngeal ganglion, from which a fused
pair of nerve cords runs posteriorly.
Chaetae. Each segment has four pairs of
chaetae, bristles that provide traction for
burrowing.
Many of the internal structures are repeated within each segment of
the earthworm.
Giant Australian earthworm
Clitellum
Earthworm anatomy
Polychaetes Members of class Polychaeta possess
paddlelike parapodia that function as gills and aid in locomotion
Parapodia
Leeches Members of class
Hirudinea are blood-sucking parasites, such as leeches
Nematodes (roundworms)
Nematodes are nonsegmented pseudocoelomates covered by a tough cuticle
Among the most widespread of all animals, nematodes, or roundworms Are found in most aquatic
habitats, in the soil, in moist tissues of plants, and in the body fluids and tissues of animals
Nematode movie
Nematodes The cylindrical bodies of nematodes are
covered by a tough coat called a cuticle
25 µm
Nematodes Some species of nematodes are important
parasites of plants and animals50 µmEncysted juveniles Muscle tissue
Trichinella spiralis encysted in human muscle tissue
Arthropods
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 ArthropodaAre found in nearly all habitats of the biosphere
Arthropod Characteristics The diversity and success of arthropods
Are largely related to their segmentation, hard exoskeleton, and jointed appendages
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 The body of an arthropod is completely covered
by the cuticle, an exoskeleton made of chitin When an arthropod grows it molts its
exoskeleton in a process called ecdysis
Segmentation Early arthropods, such as trilobites
showed little variation from segment to segment
As arthropods evolved the segments fused, and the appendages became more specialized
The appendages of some living arthropods are modified for many different functions
Antennae(sensoryreception)
Head Thorax
Swimmingappendages
Walking legs
Mouthparts (feeding)Pincer (defense)
AbdomenCephalothorax
Subphyla of Arthropoda
Cheliceriforms Named for clawlike
feeding appendages called chelicerae Includes spiders, ticks,
mites, scorpions, and horseshoe crabs
Most of the marine cheliceriforms are extinct But some species
survive today, including the horseshoe crabs
Scorpions have pedipalps that are pincers specialized for defense and the capture of food. The tip of the tail bears a poisonous stinger.
(a) Dust mites are ubiquitous scavengers in human dwellings but are harmless except to those people who are allergic to them (colorized SEM).
(b) Web-building spiders are generally most active during the daytime.
(c)
50 µm
Cheliceriforms Most modern cheliceriforms are
arachnids A group that includes spiders,
scorpions, ticks, and mites
Arachnids Arachnids have an abdomen and a cephalothorax
Which has six pairs of appendages, the most anterior of which are the chelicerae. (4 pairs of walking legs)
Digestivegland
Intestine
HeartStomach
Brain
Eyes
Poisongland
PedipalpChelicera
Book lung
Spermreceptacle
Gonopore(exit for eggs)Silk gland
Spinnerets
Anus
Ovary
Myriapods
Subphylum Myriapoda Includes millipedes and
centipedes Millipedes, class Diplopoda
Have a large number of legs Each trunk segment has two
pairs of legs Centipedes, class
Chilopoda Are carnivores with jaw-like
mandibles Have one pair of legs per
trunk segment
Insects Subphylum Hexapoda, insects and their
relativesAre more species-rich than all other forms of
life combinedLive in almost every terrestrial habitat and in
fresh waterThe internal anatomy of an insect includes
several complex organ systems
Insect anatomy
Compound eye
Antennae
Anus
Vagina
OvaryDorsalartery Crop
Abdomen Thorax Head
The insect body has three regions: head, thorax, and abdomen. The segmentation of the thorax and abdomen are obvious, but the segments that form the head are fused.
Heart. The insect heart drives hemolymph through an open circulatory system.
Cerebral ganglion. The two nerve cords meet in the head, where the ganglia of several anterior segments are fused into a cerebral ganglion (brain). The antennae, eyes, and other sense organs are concentrated on the head.
Tracheal tubes. Gas exchange in insects is accomplished by a tracheal system of branched, chitin-lined tubes that infiltrate the body and carry oxygen directly to cells. The tracheal system opens to the outside of the body through spiracles, pores that can control air flow and water loss by opening or closing.
Nerve cords. The insect nervous system consists of a pair of ventral nerve cords with several segmental ganglia.
Insect mouthparts are formed from several pairs of modified appendages. The mouthparts include mandibles, which grasshoppers use for chewing. In other insects, mouthparts are specialized for lapping, piercing, or sucking.
Malpighian tubules. Metabolic wastes are
removed from the hemolymph by excretory organs called Malpighian
tubules, which are out-pocketings of the
digestive tract.
Insects Flight is one key to the great success of
insectsAn animal that can fly can escape predators,
find food, and disperse to new habitats much faster than organisms that can only crawl
Metamorphosis
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 (example: grasshoppers) Insects with complete metamorphosis have larval stages
specialized for eating and growing that are known by such names as maggot, grub, or caterpillar
The larval stage looks entirely different from the adult stage Metamorphosis from the larval stage to the adult stage
occurs during a pupal stage
Metamorphosis
Larva (caterpillar)(a)(b) Pupa
(c) Pupa(d) Emerging adult
(e) Adult
movie
26 Orders of InsectsORDER
Blattodea 4,000 Cockroaches have a dorsoventrally flattened body, with legs modified for rapid running. Forewings, when present, areleathery, whereas hind wings are fanlike. Fewer than 40 cock-roach species live in houses; the rest exploit habitats ranging from tropical forest floors to caves and deserts.
Beetles comprise the most species-rich order of insects. They have two pairs of wings, one of which is thick and leathery, theother membranous. They have an armored exoskeleton andmouthparts adapted for biting and chewing. Beetles undergocomplete metamorphosis.
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. Earwigshave biting mouthparts and large posterior pincers. They un-dergo incomplete metamorphosis.
Dipterans have one pair of wings; the second pair has become modified into balancing organs called halteres. Their head islarge and mobile; their mouthparts are adapted for sucking,piercing, or lapping. Dipterans undergo complete metamorpho-sis. Flies and mosquitoes are among the best-known dipterans, which live as scavengers, predators, and parasites.
Hemipterans are so-called “true bugs,” including bed bugs, assassin bugs, and chinch bugs. (Insects in other orders aresometimes erroneously called bugs.) Hemipterans have two pairs of wings, one pair partly leathery, the other membranous.They have piercing or sucking mouthparts and undergoincomplete metamorphosis.
Ants, bees, and wasps are generally highly social insects. Theyhave 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 com-plete metamorphosis.
Termites are widespread social insects that produce enormous colonies. It has been estimated that there are 700 kg oftermites for every person on Earth! Some termites have twopairs of membranous wings, while others are wingless. They feed on wood with the aid of microbial symbionts carried in specialized chambers in their hindgut.
Coleoptera 350,000
Dermaptera 1,200
Diptera 151,000
Hemiptera 85,000
Hymenoptera 125,000
Isoptera 2,000
APPROXIMATENUMBER OF
SPECIESMAIN CHARACTERISTICS EXAMPLES
Germancockroach
Japanesebeetle
Earwig
Horsefly
Leaf-Footedbug
Cicada-killer wasp
Termite
26 Orders of InsectsLepidoptera 120,000 Butterflies and moths are among the best-known insects. They
have two pairs of wings covered with tiny scales. To feed, theyuncoil a long proboscis. Most feed on nectar, but some species feed on other substances, including animal blood or tears.
Odonata5,000 Dragonflies and damselflies have two pairs of large, membran-
ous wings. They have an elongated abdomen, large, compound eyes, and chewing mouthparts. They undergo incomplete meta-morphosis and are active predators.
Orthoptera 13,000 Grasshoppers, crickets, and their relatives are mostly herbi-vorous. They have large hind legs adapted for jumping, twopairs 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 on their hind leg. Orthopterans undergo incomplete metamorphosis.
Phasmida 2,600 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.
Phthiraptera 2,400 Commonly called sucking lice, these insects spend their entire life as an ectoparasite feeding on the hair or feathers of a singlehost. Their legs, equipped with clawlike tarsi, are adapted forclinging to their hosts. They lack wings and have reduced eyes.Sucking lice undergo incomplete metamorphosis.
Siphonaptera 2,400 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.
Thysanura 450 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.
Trichoptera 7,100 The larvae of caddisflies live in streams, where they make houses from sand grains, wood fragments, or other material held to-gether by silk. Adults have two pairs of hairy wings and chewingor lapping mouthparts. They undergo complete metamorphosis.
Swallowtailbutterfly
Dragonfly
Katydid
Stick insect
HumanBodylouse
Flea
Silverfish
Caddisfly
ORDERAPPROXIMATE
NUMBER OFSPECIES
MAIN CHARACTERISTICS EXAMPLE
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 biramous (branched) appendages that are extensively specialized for feeding and locomotion
Decapods Decapods are all relatively large crustaceans
And include lobsters, crabs, crayfish, and shrimp
Ghost crabs (genus Ocypode) live on sandy ocean beaches worldwide. Primarily nocturnal, they take shelter in burrows during the day.
Decapod movie
Planktonic crustaceans
Planktonic crustaceans include many species of copepods Which are among the most
numerous of all animals
Planktonic crustaceans known as krill are consumed in vast quantities by whales.
Barnacles Barnacles are a group of mostly sessile crustaceans
whose cuticle is hardened into a shell
The jointed appendages projecting from the shellsof these barnacles capture organisms and organic particles suspended inthe water.
Deuterostomes
Echinoderms and chordates are deuterostomes
Chordates and echinoderms share the characteristics of deuterostomesRadial cleavageFormation of the mouth at the end of the
embryo opposite the blastopore
Echinoderms
Echinoderm characteristics 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
network of hydraulic canals branching into tube feet that function in locomotion, feeding, and gas exchange
Echinoderm movie
Echinoderm anatomy
StomachAnus
Ringcanal
Gonads
AmpullaPodium
Radialnerve
Tubefeet
Spine
Gills
A short digestive tract runs from the mouth on the bottom of the central disk to the anus on top of the disk.
The surface of a sea star is covered by spines that help defend against predators, as well as by small gills that provide gas exchange.
Madreporite. Water can flow in or out of the water vascular system into the surrounding water through the madreporite.
Branching from each radial canal are hundreds of hollow, muscular tube feet filled with fluid. Each tube foot consists of a bulb-like ampulla and suckered podium (foot portion). When the ampulla squeezes, it forces water into the podium and makes it expand. The podium then contacts the substrate. When the muscles in the wall of the podiumcontract, they force water back into the ampulla, making the podium shorten and bend.
Radial canal. The water vascular system consists of a ring canal in the central disk and five radial canals, each running in a groove down the entire length of an arm.
Digestive glands secrete digestive juices and aid in
the absorption and storage of nutrients.
Central disk. The central disk has a nerve ring and
nerve cords radiating from the ring into the arms.
Echinoderm classes
Sea Stars
Sea stars, class AsteroideaHave multiple arms radiating from a central diskThe undersurfaces of the arms bear tube feet,
each of which can act like a suction disk
(a) A sea star (class Asteroidea)
Brittle Stars Brittle stars have a distinct central disk and
long, flexible arms
(b) A brittle star (class Ophiuroidea)
Sea Urchins and Sand Dollars Sea urchins and sand dollars have no
arms, but they do have five rows of tube feet that function in movement
Sea Urchin
Sand Dollar
Sea Lilies and Feather Stars Sea lilies live attached to the substrate by a stalk Feather stars
Crawl about using their long, flexible arms
(d) A feather star (class Crinoidea)
Sea Cucumbers Sea cucumbers do not look much like
other echinodermsThey lack spines, and their endoskeleton is
much reduced
(e) A sea cucumber (class Holothuroidea)
Sea Daisies Sea daisies were discovered in 1986
And only two species are known
(f) A sea daisy (class Concentricycloidea)
Chordates (Phylum Chordata) Chordates
Two subphyla of invertebrates as well as the hagfishes and the vertebrates
Share many features of embryonic development with echinoderms
Review of Animal Phyla