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IB-202-5. 3-17-06. Cephalopods. Class Cephalopoda includes squids and octopuses Carnivores with beak-like jaws surrounded by tentacles. Foot modified to form siphon, tentacles and head. Closed circulatory system Well developed eye similar to vertebrate eye (lens, retina etc)

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Ib 202 5 l.jpg



Cephalopods l.jpg

  • Class Cephalopoda includes squids and octopuses

    • Carnivores with beak-like jaws surrounded by tentacles. Foot modified to form siphon, tentacles and head.

    • Closed circulatory system

    • Well developed eye similar to vertebrate eye (lens, retina etc)

    • Very active life style. Squid can feed on herring by zipping through a school. Herring capable of rapid swimming.

    • Elaborate sex where male inserts packets of sperm into mantle cavity of female.

    • Ink gland for escape.

    • Can teach octopus simple tasks. Can crawl out of their tanks into another eat the crabs and return to their own

Slide3 l.jpg

(a) Octopuses are considered among the

most intelligent invertebrates.

Figure 33.22a

  • Most octopuses

    • Creep along the sea floor in search of prey. Some have toxin associated with their bite. Very good at changing color so they are camouflaged in nature.

Slide4 l.jpg

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

Figure 33.22b

  • Squids use their siphon

    • To fire a jet of water, which allows them to swim very quickly

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Wednesday, 15 Jan., 2003, 16:50 GMT

Giant squid Architeutis dux

'attacks French boat'

….De Kersauson says his squid was

three times as big

…..two of the tentacles were blocking

the rudder.

…. the squid must have been seven or

eight metres (22 to 26 feet) long.

…. we weren't going to attack it with our


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Wednesday, 28 September 2005, 05:42 GMT

Live giant squid caught on camera

Japan's Ogasawara Islands

8m-long Architeuthis

Slide7 l.jpg

(c) Chambered nautiluses are the only living cephalopods with an external shell. Have rudimentary eye without lens like a pin hole camera. Shell is chambered and put less dense ammonium chloride in chamber for flotation. Less dense than seawater.

Figure 33.22c


  • One small group of shelled cephalopods

    • The chambered nautiluses, survives today

    • Huge nautilus fossils in northern Africa

General characteristics of phylum arthropoda l.jpg
General Characteristics of Phylum Arthropoda

  • The diversity and success of arthropods.

  • Find them in fresh water, the ocean and the land and air.

    • Are largely related to their segmentation, hard chitinous exoskeleton, and the specialization jointed appendages for specific functions.

Common fossil trilobite l.jpg

Figure 33.28

Common fossil trilobite

  • Early arthropods, such as trilobites

    • Showed little variation from segment to segment and no specialized appendages

Specialization of appendages in modern forms l.jpg










Walking legs

Figure 33.29

Pincer (defense)

Mouthparts (feeding)

Specialization of appendages in modern forms

  • As arthropods evolved

    • The segments fused, and the appendages became more specialized

  • The appendages of some living arthropods

    • Are modified for many different functions as seen in the lobster below (describe specialization)

Thick exoskeleton l.jpg
Thick exoskeleton

  • The body of an arthropod

    • is completely covered by the cuticle, an exoskeleton made of chitin (polyglucoseamine). Hardened claws of skeletons composed of protein, chitin and calcium carbonate

  • When an arthropod grows its soft body becomes too large for its exoskeleton

    • Thus it sheds or molts its exoskeleton in a process called ecdysis. Then it grows a new one. Its exoskeleton is very soft until the chitinous polymers become cross linked which hardens the cuticle.

Physiological systems l.jpg
Physiological Systems

  • Arthropods have an open circulatory system

    • in which fluid called hemolymph is circulated into the spaces surrounding the tissues and organs. Tube like heart. Presence of oxygen binding pigments (hemocyanin-blue)

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

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Table 33.5

  • Molecular evidence now suggests

    • That living arthropods consist of four major lineages that diverged early in the evolution of the phylum (divided into subphyla)

Cheliceriforms l.jpg

  • Subphylum Cheliceriformes

    • Are named for clawlike feeding appendages called chelicerae

    • Include spiders, ticks, mites, scorpions, and horseshoe crabs

Horseshoe crab l.jpg

Figure 33.30

Horseshoe Crab

  • Most of the marine cheliceriforms are extinct

    • But some species survive today, including the horseshoe crabs (laboratory experimental animal for demonstrating osmotic conformity)

Scorpions mites and spiders l.jpg

50 µm




Scorpions have pedipalps that are pincers

specialized for defense and the capture of

food. The tip of the tail bears a poisonous


Dust mites are ubiquitous scavengers in

human dwellings but are harmless except

to those people who are allergic to them

(colorized SEM).

Web-building spiders are generally

most active during the daytime.

Figure 33.31a–c

Scorpions, mites and spiders

  • Most modern cheliceriforms are arachnids

    • A group that includes spiders, scorpions, ticks, and mites

Anatomy of a spider l.jpg












Book lung





(exit for eggs)



Silk gland

Figure 33.32

Anatomy of a spider

  • Arachnids have an abdomen and a cephalothorax

    • Which has six pairs of appendages, the most anterior of which are the chelicerae (special structures)

Spiders digest there food outside of their body l.jpg

Spiders digest there food outside of their body

They stab prey with their fangs, inject toxins and enzymes that digest tissues. Then they suck up the partially digested material as a fluid. Some of the enzymes are phospholipases that destroy cell membranes.

Thus spider bites can develop into lesions and tissue can become necrotic. Not sure why these enzymes can have such a long half life (in case of snakes give antivenom injections).

Subphylum myriapoda includes millipedes and centipedes l.jpg

Figure 33.33

Subphylum MyriapodaIncludes millipedes and centipedes

  • Millipedes, class Diplopoda

    • have a large number of legs

  • Each trunk segment

    • has two pairs of legs-eats plant material and detritus

Slide20 l.jpg

Figure 33.34

  • Centipedes, class Chilopoda

    • Are carnivores with jaw-like mandibles

    • Have one pair of legs per trunk segment

    • Poison claws on foremost trunk segment

Insects l.jpg

  • Subphylum Hexapoda, insects and their relatives

    • Are more species-rich than all other forms of life combined

    • Live in almost every terrestrial habitat,in fresh water and a few on the surface of the ocean.

    • A few found in Antarctica where there are only mosses to feed on.

Insect anatomy l.jpg

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.

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.

Heart. The

insect heart

drives hemolymph

through an

open circulatory





Compound eye






Malpighian tubules.

Metabolic wastes are

removed from the

hemolymph by excretory

organs called Malpighian

tubules, which are out-

pocketings of the

digestive tract.



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.

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


Nerve cords. The insect

nervous system

consists of a pair of

ventral nerve cords

with several

segmental ganglia.

Figure 33.35

Insect Anatomy

  • Includes several complex organ systems

Insects very successful as a group l.jpg
Insects very successful as a group

  • Flight is obviously 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 (example hords of grasshoppers that strip vegetation in African lands from time to time. Also in US, but we stop them with insect sprays.

Insect reproduction l.jpg
Insect Reproduction

  • Insects have internal fertilization. Lay eggs. Development of many involve juvenile stages that are very different from the adult

  • 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

Slide25 l.jpg

  • 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

Complete metamorphosis l.jpg


Larva (caterpillar)

(b) Pupa

(c) Pupa

(d) Emerging adult

(e) Adult

Figure 33.6a–e

Complete metamorphosis

  • Metamorphosis from the larval stage to the adult stage

    • Occurs during a pupal stage

Slide27 l.jpg









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 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, the

other membranous. They have an armored exoskeleton and

mouthparts adapted for biting and chewing. Beetles undergo

complete 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. Earwigs

have 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 is

large 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 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.






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 com-

plete metamorphosis.

Cicada-killer wasp



Termites are widespread social insects that produce enormous

colonies. It has 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.


Figure 33.37

  • Insects are classified into about 26 orders

Slide28 l.jpg









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.




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.



Grasshoppers, crickets, and their relatives are mostly herbi-

vorous. 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 on their hind

leg. Orthopterans undergo incomplete metamorphosis.






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.

Stick insect



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.






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.




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.




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 chewing

or lapping mouthparts. They undergo complete metamorphosis.


Figure 33.37

  • Insects are classified into about 26 orders

Class crustacea l.jpg
Class Crustacea

  • While arachnids and insects thrive on land

    • Crustaceans, for the most part, have remained in marine and freshwater environments

Slide30 l.jpg

Slide31 l.jpg


Ghost crabs (genus Ocypode) live on sandy ocean

beaches worldwide. Primarily nocturnal, they take

shelter in burrows during the day. Note stalked eyes.

Figure 33.38a

  • Decapods (10 walking legs) are all relatively large crustaceans

    • And include lobsters, crabs, crayfish, and shrimp

Slide32 l.jpg

Planktonic crustaceans

known as krill are

consumed in vast

quantities by whales.


Figure 33.38b

  • Planktonic crustaceans include many species of copepods. Plankton found in surface waters of ocean either drifting or weakly swimming. Moved along by the oceanic currents. Euphausids (krill) fed on my baleen whales (filter out 5 cm long krill). Baleen is composed of horny strips in the mouth of whales with fibers projecting from it to act as a filter. No teeth in these whales although the fetus does have teeth but looses them during maturation.

Slide33 l.jpg

The jointed appendages (modified legs)

projecting from the shells of these barnacles capture

organisms and organic particles suspended in

the water. Stand on their heads and glue

themselves to rocks with their antennae. Some form

Stalks like in picture, others not (example).


Figure 33.38c

  • Barnacles are a group of mostly sessile crustaceans

    • Whose cuticle is hardened into a shell composed mostly of calcium carbonate.

    • (Ships and whales-rocky intertidal full of barnacles)

Phylum echinodermata star fish sea urchins and sea cucumbers l.jpg
Phylum Echinodermata (star fish, sea urchins and sea cucumbers)

  • Echinoderms and chordates are deuterostomes

  • At first glance, sea stars and other echinoderms may seem to have little in common with phylum Chordata, which includes the vertebrates

Chordates and echinoderms share characteristics of deuterostomes l.jpg
Chordates and echinoderms share characteristics of deuterostomes

  • Radial cleavage

  • Development of the coelom from the archenteron (enterocoelus)

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

Echinoderms l.jpg
Echinoderms deuterostomes

  • 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

    • Most have a water vascular system used for movement

Anatomy of a starfish l.jpg

A short digestive tract runs from the deuterostomes

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.

Central disk. The central

disk has a nerve ring and

nerve cords radiating from

the ring into the arms.





Madreporite. Water can flow

in or out of the water vascular

system into the surrounding

water through the madreporite.



Digestive glands secrete

digestive juices and aid in

the absorption and storage

of nutrients.








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 podium

contract, 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.

Figure 33.39

Anatomy of a Starfish

  • 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

Why are echinoderms placed near the chordates in view of their radial anatomy l.jpg
Why are echinoderms placed near the chordates in view of their radial anatomy???

  • The radial anatomy of many echinoderms (not symmetry) evolved secondarily from the bilateral symmetry of ancestors (madreporite off center).

Slide39 l.jpg

Table 33.6 their radial anatomy???

  • Living echinoderms are divided into six classes

Sea stars l.jpg

Figure 33.40a their radial anatomy???

(a) A sea star (class Asteroidea)

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

Brittle stars l.jpg

(b) A brittle star (class Ophiuroidea) their radial anatomy???

Figure 33.40b

Brittle Stars

  • Brittle stars have a distinct central disk

    • And long, flexible arms

Sea urchins and sand dollars l.jpg

(c) A sea urchin (class Echinoidea) their radial anatomy???

Figure 33.40c

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 (laboratory sea urchin reproduction)

Crinoides feather stars l.jpg

(d) A feather star (class Crinoidea) their radial anatomy???

Figure 33.40d

Crinoides (Feather stars)

  • Move about slowly using their roots on the disc. Use feathery arms to swim. Alternately pump them up and down. Fossil forms were stalked crinoides.

Sea cucumbers l.jpg

Figure 33.40e their radial anatomy???

(e) A sea cucumber (class Holothuroidea)

Sea Cucumbers

  • Sea cucumbers

    • Upon first inspection do not look much like other echinoderms

    • Have tube feet, but lack spines, and their endoskeleton is much reduced.

    • Served as an expensive dinner food at Chinese banquets-gelatinous. Dried, rehydrated then braised in abolone sauce.

Sea daisies l.jpg

(f) A sea daisy (class Concentricycloidea) their radial anatomy???

Figure 33.40f

Sea Daisies

  • Sea daisies were discovered in 1986

    • And only two species are known live on water soaked wood

Chordates l.jpg
Chordates their radial anatomy???

  • Phylum Chordata

  • Consists of two subphyla of invertebrates as well as the hagfishes and the vertebrates

  • Shares many features of embryonic development with echinoderms

Slide47 l.jpg

Table 33.7 their radial anatomy???

  • A summary of animal phyla