Download Chapter_29_Part_2_AP_Biology_modified

Overview: Life Without a Backbone
• Invertebrates are animals that lack a backbone
• They account for 95% of known animal species
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Sponges are suspension feeders, capturing food
particles suspended in the water that passes
through their body
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 33-4
Food particles
in mucus
Choanocyte
Flagellum
Choanocytes
Collar
Osculum
Azure vase sponge
(Callyspongia plicifera)
Spongocoel
Phagocytosis of
food particles Amoebocyte
Porocytes
Spicules
Epidermis
Water
flow
Amoebocyte
Mesohyl
• 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• 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)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 33-5
Mouth/anus
Polyp
Tentacle
Medusa
Gastrovascular
cavity
Gastrodermis
Body
stalk
Mesoglea
Epidermis
Tentacle
Mouth/anus
• 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 33-6
Prey
Tentacle
“Trigger”
Nematocyst
Coiled thread
Discharge
of thread
Cnidocyte
• Phylum Cnidaria is divided into four major classes:
– Hydrozoa
– Scyphozoa
– Cubozoa
– Anthozoa
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 33-7
Scyphozoans (jellies)
Hydrozoans
Cubozoan (sea wasp)
Anthozoan
(sea anemone)
Hydrozoans
• Most hydrozoans alternate between polyp and
medusa forms
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 33-8–3
Reproductive
polyp
Feeding
polyp
Medusa
bud
MEIOSIS
Gonad
Medusa
Egg
SEXUAL
REPRODUCTION
Sperm
ASEXUAL
REPRODUCTION
(BUDDING)
Portion of
a colony
of polyps
FERTILIZATION
Zygote
Developing
polyp
Mature
polyp
Planula
(larva)
1 mm
Key
Haploid (n)
Diploid (2n)
Scyphozoans
• In the class Scyphozoa, jellies (medusae) are the
prevalent form of the life cycle
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Cubozoans
• In the class Cubozoa, which includes box jellies
and sea wasps, the medusa is box-shaped and
has complex eyes
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Anthozoans
• Class Anthozoa includes the corals and sea
anemones, which occur only as polyps
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Flatworms are divided into four classes:
– Turbellaria (mostly free-living flatworms)
– Monogenea (monogeneans)
– Trematoda (trematodes, or flukes)
– Cestoda (tapworms)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Turbellarians
• Turbellarians are nearly all free-living and mostly
marine
• The best-known turbellarians are commonly called
planarians
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Planarians have light-sensitive eyespots and
centralized nerve nets
• The planarian nervous system is more complex
and centralized than the nerve nets of cnidarians
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 33-10
Pharynx
Gastrovascular
cavity
Eyespots
Ganglia
Ventral nerve cords
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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
• Most monogeneans are parasites of fish
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Tapeworms
• Tapeworms are also parasitic and lack a digestive
system
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 33-12
Proglottids with
reproductive structures
200 µm
Scolex
Hooks
Sucker
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• All molluscs have a similar body plan with three
main parts:
– Muscular foot
– Visceral mass
– Mantle
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 33-16
Visceral mass
Coelom
Heart
Intestine
Nephridium
Gonads
Mantle
Stomach
Mantle
Shell
cavity
Radula
Anus
Gill
Foot
Nerve
cords
Esophagus
Mouth
Radula
Mouth
• 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• 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)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Chitons
• Class Polyplacophora consists of the chitons,
oval-shaped marine animals encased in an armor
of eight dorsal plates
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Gastropods
• About three-quarters of all living species of
molluscs belong to class Gastropoda
Video: Nudibranchs
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 33-18
A land snail
A sea slug. Nudibranchs, or sea slugs,
lost their shell during their evolution.
• 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 33-19
Mantle
cavity
Anus
Mouth
Stomach
Intestine
Bivalves
• Molluscs of class Bivalvia include many species of
clams, oysters, mussels, and scallops
• They have a shell divided into two halves
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• The mantle cavity of a bivalve contains gills that
are used for feeding as well as gas exchange
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 33-21
Coelom
Hinge area
Mantle
Gut
Heart
Adductor
muscle
Shell
Anus
Mouth
Excurrent
siphon
Palp
Water
flow
Foot
Mantle
cavity
Gill
Incurrent
siphon
Cephalopods
• Class Cephalopoda includes squids and
octopuses, carnivores with beak-like jaws
surrounded by tentacles of their modified foot
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Most octopuses creep along the sea floor in
search of prey
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 33-22a
Octopuses are considered among the
most intelligent invertebrates.
• Squids use their siphon to fire a jet of water, which
allows them to swim very quickly
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 33-22b
Squids are speedy carnivores
with beaklike jaws and welldeveloped eyes.
• One small group of shelled cephalopods, the
nautiluses, survives today
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 33-22c
Chambered nautiluses are the only living
cephalopods with an external shell.
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)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 33-23
Cuticle
Epidermis
Circular muscle
Longitudinal muscle
Coelom
Septum (partition
between segments)
Metanephridium
Anus
Dorsal vessel
Chaetae
Intestine
Nerve Ventral vessel
cords
Nephrostome
Clitellum
Esophagus
Crop
Pharynx
Giant Australian earthworm
Cerebral ganglia
Intestine
Gizzard
Mouth
Subpharyngeal
ganglion
Metanephridium
Circulatory
system
Ventral nerve cords
with segmental
ganglia
Polychaetes
• Members of class Polychaetes have paddlelike
parapodia that work as gills and aid in locomotion
Video: Tubeworms
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 33-24
Parapodia
Leeches
• Members of class Hirudinea are blood-sucking
parasites, such as leeches
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 33-26
25 µm
• Some species of nematodes are important
parasites of plants and animals
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 33-27
Encysted juveniles
Muscle tissue
50 µm
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
General Characteristics of Arthropods
• The diversity and success of arthropods are
largely related to their segmentation, hard
exoskeleton, and jointed appendages
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Early arthropods, such as trilobites, showed little
variation from segment to segment
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 33-29
Cephalothorax
Abdomen
Thorax
Antennae
(sensory
reception)
Head
Swimming
appendages
(two sets
located under
abdomen
Walking legs
Pincer (defense)
Mouthparts (feeding)
• 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• 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)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Most modern cheliceriforms are arachnids, which
include spiders, scorpions, ticks, and mites
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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
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
Web-building spiders are generally
most active during the daytime.
• Arachnids have an abdomen and a cephalothorax,
which has six pairs of appendages, the most
anterior of which are the chelicerae
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 33-32
Stomach
Intestine
Brain
Heart
Digestive
gland
Eyes
Ovary
Poison
gland
Anus
Book lung
Gonopore
(exit for eggs) Sperm
Silk gland
receptacle
Spinnerets
Chelicera
Pedipalp
Myriapods
• Subphylum Myriapoda includes millipedes and
centipedes
• Millipedes, class Diplopoda, have many legs
• Each trunk segment has two pairs of legs
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Centipedes, class Chilopoda, are carnivores with
jaw-like mandibles
• They have one pair of legs per trunk segment
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 33-35
Abdomen
Thorax Head
Compound eye
Antennae
Dorsal
artery
Crop
Cerebral ganglion
Heart
Anus
Vagina
Malpighian tubules
Ovary
Tracheal tubes
Nerve cords
Mouthparts
• 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 33-36
Larva (caterpillar)
Pupa
Pupa
Emerging adult
Adult
• Insects are classified into about 26 orders
Video: Bee Pollinating
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 33-37aA
ORDER
Blattodea
APPROXIMATE
NUMBER OF
SPECIES
4,000
MAIN CHARACTERISTICS
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.
EXAMPLES
German
cockroach
LE 33-37bA
ORDER
Coleoptera
APPROXIMATE
NUMBER OF
SPECIES
350,000
MAIN CHARACTERISTICS
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.
EXAMPLES
Japanese
beetle
LE 33-37cA
ORDER
Dermaptera
APPROXIMATE
NUMBER OF
SPECIES
1,200
MAIN CHARACTERISTICS
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.
EXAMPLES
Earwig
LE 33-37dA
ORDER
Diptera
APPROXIMATE
NUMBER OF
SPECIES
151,000
MAIN CHARACTERISTICS
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.
EXAMPLES
Horsefly
LE 33-37eA
ORDER
Hemiptera
APPROXIMATE
NUMBER OF
SPECIES
85,000
MAIN CHARACTERISTICS
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.
EXAMPLES
Leaffooted
bug
LE 33-37fA
ORDER
Hymenoptera
APPROXIMATE
NUMBER OF
SPECIES
125,000
MAIN CHARACTERISTICS
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.
EXAMPLES
Cicada-killer wasp
LE 33-37gA
ORDER
Isoptera
APPROXIMATE
NUMBER OF
SPECIES
2,000
MAIN CHARACTERISTICS
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.
EXAMPLES
Termite
LE 33-37aB
ORDER
Lepidoptera
APPROXIMATE
NUMBER OF
SPECIES
120,000
MAIN CHARACTERISTICS
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.
EXAMPLES
Swallowtail
butterfly
LE 33-37bB
ORDER
Odonata
APPROXIMATE
NUMBER OF
SPECIES
5,000
MAIN CHARACTERISTICS
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.
EXAMPLES
Dragonfly
LE 33-37cB
ORDER
Orthoptera
APPROXIMATE
NUMBER OF
SPECIES
13,000
MAIN CHARACTERISTICS
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.
EXAMPLES
Katydid
LE 33-37dB
ORDER
Phasmida
APPROXIMATE
NUMBER OF
SPECIES
2,600
MAIN CHARACTERISTICS
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.
EXAMPLES
Stick insect
LE 33-37eB
ORDER
Phthiraptera
APPROXIMATE
NUMBER OF
SPECIES
2,400
MAIN CHARACTERISTICS
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.
EXAMPLES
Human
body
louse
LE 33-37fB
ORDER
Siphonaptera
APPROXIMATE
NUMBER OF
SPECIES
2,400
MAIN CHARACTERISTICS
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.
EXAMPLES
Flea
LE 33-37gB
ORDER
Thysanura
APPROXIMATE
NUMBER OF
SPECIES
450
MAIN CHARACTERISTICS
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.
EXAMPLES
Silverfish
LE 33-37hB
ORDER
Trichoptera
APPROXIMATE
NUMBER OF
SPECIES
7,100
MAIN CHARACTERISTICS
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.
EXAMPLES
Caddisfly
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Decapods are all relatively large crustaceans and
include lobsters, crabs, crayfish, and shrimp
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Planktonic crustaceans include many species of
copepods, which are among the most numerous
of all animals
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Barnacles are a group of mostly sessile
crustaceans
• They have a cuticle that is hardened into a shell
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Echinoderms
• Sea stars and most other echinoderms are slowmoving 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 33-39
Spine
Anus Stomach
Gills
Central disk
Madreporite
Digestive glands
Radial
nerve
Ring
canal
Gonads
Ampulla
Radial canal
Podium
Tube
feet
• 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)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 33-40a
A sea star (class Asteroidea)
Brittle Stars
• Brittle stars have a distinct central disk and long,
flexible arms
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 33-40b
A brittle star (class Ophiuroidea)
Sea Urchins and Sand Dollars
• Sea urchins and sand dollars have no arms but
have five rows of tube feet
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 33-40c
A sea urchin (class Echinoidea)
Sea Lilies and Feather Stars
• Sea lilies live attached to the substrate by a stalk
• Feather stars crawl using long, flexible arms
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 33-40d
A feather star (class Crinoidea)
Sea Cucumbers
• Sea cucumbers do not look much like other
echinoderms
• They lack spines, and their endoskeleton is much
reduced
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 33-40e
A sea cucumber (class Holothuroidea)
Sea Daisies
• Sea daisies were discovered in 1986, and only
two species are known
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 33-40f
A sea daisy (class Concentricycloidea)
Chordates
• Phylum Chordata consists of two subphyla of
invertebrates as well as hagfishes and vertebrates
• Chordates share many features of embryonic
development with echinoderms
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings