Chapter 33Invertebrates

I.  Parazoa            A.  Phylum Porifera:  Sponges Figure 33.2 (p. 647, ed. 6) – A sponge.  1.  Non-moving (sessile) animals 2.  No nerves or muscles (no tissue differentiation) 3.  Mostly marine 4.  Filter feeders:  Collect food particles from water: Remember cells involved in feeding - Figure 33.3 (p. 648, ed. 6; Fig 33.4, p. 642, ed. 7) – Anatomy of a sponge. 5.  Most sponges are hermaphrodites.  Hermaphrodites function as both male and female in sexual reproduction by producing eggs and sperm.  **All other animals are in the clade Eumetazoa (true tissues).**

 Figure 33.4 (p. 649, ed. 6; Fig. 33.5, p. 642, ed. 7) – Polyp and medusa forms of cnidarians.  1.  Radial symmetry with central digestive (gastrovascular) cavity.  2.  One opening in the gastrovascular cavity serves as both mouth and anus.                        3.  Survive as carnivores. 

 4.  Phylum name comes from specialized cells called cnidocytes.  Cnidocytes are stinging cells used for defense and to capture prey.         Figure 33.5 (p. 649) – A cnidocyte of a hydra.

            B.  Phylum Ctenophora:  Comb jellies                          Figure 33.8 (p. 651) – A ctenophore, or comb jelly.                         1.  Resemble cnidarian medusas.                         2.  Use cilia for locomotion.

III.  Protostomia:  Lophotrochozoa            A.  Phylum Platyhelminthes:  Flatworms                        1.  Sizes range from microscopic up to 20 meters long (tapeworms).  2.  Many are parasites. Table 33.2 (p. 652, ed. 6; p. 646, ed. 7) – Classes of Phylum Platyhelminthes

                        3.  There are four classes of flatworms; know the common names.                                    a.  Turbellarians                                                i.  Mostly free-living (non-parasitic)ii.  Feed on small animals, dead animalsiii.  Very flat for O2 exchange.  They have no gas exchange

organs.                         Figure 33.10 (p. 653) – Anatomy of a planarian.

b,c.  Monogenea/Trematoda                                               i.  Live as parasitesii.  Trematodes parasitize vertebrates.  For example, humans but often with intermediate hosts.    Figure 33.11 (p. 653, ed. 6; p. 647, ed. 7) – The life history of a blood fluke (Schistosoma mansoni). 

 d.  Cestoidea – Tapeworms                                                 i.  Live as parasitesii.  Head contains suckers and hooks that lock onto the intestinal lining of the host.iii.  The rest of the body is mostly units called proglottids that are sex organs.iv.  Eggs transferred to new hosts by consuming fecal contaminated water.    Figure 33.12 (p. 654) – Anatomy of a tapeworm.

            B.  Phylum Rotifera:  Rotifers                        1.  Aquatic 2.  Sizes range from 0.5 to 2 mm 3.  Complete digestive tract  Figure 33.13 (p. 654) – A rotifer.

            C.  Lophophorate Phyla:  Bryozoans (Ectoprocts, ed. 7), Phoronids, and Brachiopods                        1.  All of these groups have a lophophore.  The lophophore is a horseshoe shaped fold near the mouth that is surrounded by ciliated tentacles.  2.  Bryozoans resemble mosses.                                      - They have a hard exoskeleton.                                    - They are important as reef builders.                         Figure 33.14a (p. 655; p. 649, ed. 7) – A bryozoan (Lophophorates).

                        3.  Phoronids are marine worms.                         4.  Brachiopods resemble clams.                         Figure 33.14b (p. 655) – A brachiopod.

            D.  Phylum Nemertea:  Proboscis worms                        1.  Up to 30 meters in length                         2.  These worms have a hydraulically-operated proboscis that is used to capture prey.

Figure 33.15

E.  Phylum Mollusca:  Mollusks                        1.  Snails, clams, octopi, squids, oysters  2.  There are at least 150,000 known species  3.  All mollusks have similar body plans:                                    a.  Muscular foot                                    b.  Visceral mass with organs                                    c.  Mantle that secretes the shell

b.  Gastropoda – Produce shells into which the animal retreats when threatened.  Example: Snail                                     Figure 33.19 (p. 657) – Gastropods.

c.  Bivalvia – Shells divided into two parts.  Gills are used for feeding and gas exchange.  Example:  Clams, oysters      Figure 33.21 (p. 658) – Anatomy of a clam.

d.  Cephalopoda – Rapid movement; well-developed nervous systems.  Example:  Octopus, squid, nautilus                                     Figure 33.22 (p. 658) – Cephalopods.

 F.  Phylum Annelida:  Segmented worms                        1.  Sizes range from 1 mm to 3 meters in length.  2.  Each segment contains a pair of excretory tubes called metanephridia. 3.  Annelids are hermaphrodites that cross-fertilize. 4.  Three classes:                                    a.  Oligochaeta – earthworms                                     b.  Polychaeta – mostly marine                                    c.  Hirudinea – leeches 

IV.  Protostomia:  Ecdysozoa            A.  Phylum Nematoda:  Roundworms                        1.  Non-segmented                         2.  Some are important parasites of animals.                                    - Pinworms and hookworms e.g., Trichinella obtained by eating undercooked pork; juveniles infect all body organs and tissues. 

B.  Phylum Arthropoda:  Arthropods                        1.  Crustaceans, spiders, insects            2.  Hard exoskeleton, segmented bodies, jointed appendages             3.  Arthropods are the most successful of all animal phyla based on diversity, distribution, and numbers. 4.  Nearly one million species identified so far, mostly insects. 5.  The exoskeleton, or cuticle, is composed of protein and chitin. 

6.  Molting of the cuticle is called ecdysis. 7.  Extensive cephalization.  8.  Arthropods have open circulatory systems in which a heart pumps hemolymph through short arteries and into open spaces called sinuses.                        

9.  Aquatic members have gills for gas exchange.  Terrestrial members have a tracheal system branched tubes leading from the surface throughout the body.

Figure 33.26 (p. 663) – External anatomy of an arthropod.

   10.  Four evolutionary lineages:                                    a.  Trilobites – extinctb.  Chelicerates – horseshoe crabs, spidersc.  Uniramians – centipedes, millipedes, insectsd.  Crustaceans – crabs, lobsters, barnacles 

         

11.  From these lineages arose five major classes of arthropods:

                       

Table 33.5

                                   

d.  Insecta – insects

 i.  Outnumber all other forms of animals.

 ii.  Evolved flight during Carboniferous period.  Flight wasfollowed by an explosion of diversity.

 iii.  Coevolution of flowering plants and insects.

 iv.  Wings are extensions of the cuticle.

 v.  Waste is removed from hemolymph by excretory organs called malpighian tubes.  

vi.  Nervous system has a pair of ventral nerve chords that join in the head to form a cerebral ganglion (brain) that is close to the sensory organs in the head (cephalization).

 

Note: Many insects undergo metamorphosis during their development.

Incomplete metamorphosis is a process whereby the young look like the adults, but have different body proportions.

Complete metamorphosis is a process where the larval stages are specialized for eating. This stage is called a larva, maggot or grub. The adult stage is specialized for reproduction and dispersal (e.g. flight). The process of metamorphosis occurs during a pupal stage.

ORDER

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

Figure 33.37

Lepidoptera 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 13,000Grasshoppers, 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 2,600Stick 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 2,400Commonly 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

Figure 33.37

 e.  Crustacea – crabs, lobsters                     i.  40,000 species.                     ii.  Includes krill eaten by whales.

V.  Deuterostomia            A.  Phylum Echinodermata:  Echinoderms  

1.  Water vascular systems – network of hydraulic canals used for locomotion, feeding, and gas exchange.  It extends into tube feet that are used for locomotion and feeding.

 

Figure 33.38 (p. 674) – Anatomy of a sea star.

 

2.  Echinoderms appear to be radial, but are bilateral shows up in larval stages.

            B.  Phylum Chordata:  Chordates                        1.  Chordates belong to this category but will be discussed in the next chapter.