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Chapter 33 Invertebrates

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1 Chapter 33 Invertebrates


3 Phylum Porifera: Sponges are sessile with porous bodies and choanocytes
True Multicellular Org Allows for specialization of cells Intracellular digestion

4 Phylum Cnidaria: Cnidarians have radial symmetry, a gastrovascular cavity, and cnidocytes
Two layers of cells that form TISSUES - cells that act as a functional unit Gastrovascular cavity that allows for extracellular digestion - large food particles broken down so that the gastrodermis can do intracellular digestion. Simple nerve net forms nervous system - no brain


6 Hydra capturing prey Budding a form of asexual reproduction is also seen

7 Batteries of cnidocytes on the tentacles defend the animal or capture prey

8 Sea anemone

9 Soft Coral Class Anthozoa


11 1. Phylum Platyhelminthes: Flatworms are acoelomates with gastrovascular cavities
There are about 20,000 species of flatworms living in marine, freshwater, and damp terrestrial habitats. They also include many parasitic species, such as the flukes and tapeworms. Flatworms and other bilaterians are triploblastic, with a middle embryonic tissue layer, mesoderm, which contributes to more complex organs and organs systems and to true muscle tissue. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

12 Class Tubularia free living flatworm

13 Tubularia Planarian

14 Two way gut ventral nerve cords Cephalization - brain, eye spot at head gastrovascular cavity acoelomate



17 Schitstosoma mansoni the blood fluke responsible for schistosomiasis has a complex life cycle
The larvae infects snails, the fluke infects humans Class Trematoda


19 Tapeworms class Cestoidea
the head (scolex) has hooks and a sucker the proglottids are mainly made of sex organs


21 2. Phylum Rotifera: Rotifers are pseudocoelomates with jaws, crowns of cilia, and complete digestive tracts Rotifers, with about 1,800 species, are tiny animals (0.05 to 2 mm), most of which live in freshwater. Some live in the sea or in damp soil. Rotifers have a complete digestive tract with a separate mouth and anus. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

22 The word rotifer, “wheel-bearer”, refers to the crown of cilia that draws a vortex of water into the mouth. Food particles drawn in by the cilia are captured by the jaws (trophi) in the pharynx and ground up. Fig Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

23 5. Phylum Mollusca: Mollusks have a muscular foot, a visceral mass, and a mantle
The phylum Mollusca includes 150,000 known species of diverse forms, including snails and slugs, oysters and clams, and octopuses and squids. Most mollusks are marine, though some inhabit fresh water, and some snails and slugs live on land. Mollusks are soft-bodied animals, but most are protected by a hard shell of calcium carbonate. Slugs, squids, and octopuses have reduced or lost their shells completely during their evolution. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

24 Despite their apparent differences, all mollusks have a similar body plan with a muscular foot (typically for locomotion), a visceral mass with most of the internal organs, and a mantle. The mantle, which secretes the shell, drapes over the visceral mass and creates a water-filled chamber, the mantle cavity, with the gills, anus, and excretory pores. Many mollusks feed by using a straplike rasping organ, a radula, to scrape up food. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

25 Mantle secretes the shell
Radula is used for rasping food off of surfaces, but can be modified to bore holes or tear apart tough animal tissue Has trochophore larvae a type of ciliated larvae They lack true segmentation

26 The basic molluscan body plan has evolved in various ways in the eight classes of the phylum.
The four most prominent are the Polyplacophora (chitons), Gastropoda (snails and slugs), Bivalvia (clams, oysters, and other bivalves), and Cephalopoda (squids, octopuses, and nautiluses). Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

27 Chiton class Polyplacophora


29 Gastropoda is the largest molluscan class
During embryonic development it undergoes torsion which results in its asymmetrical shape

30 bivalves

31 The class Bivalvia includes clams, oysters, mussels, and scallops.
Bivalves have shells divided into two halves. The two parts are hinged at the mid-dorsal line, and powerful adductor muscles close the shell tightly to protect the animal. When the shell is open, the bivalve may extend its hatchet-shaped foot for digging or anchoring. Fig Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

32 Cephalopods have reduced or missing shells
the only molluscan with a closed circulatory system besides Ryan, the most intelligent invertebrate with a well developed nervous system and brain

33 6. Phylum Annelida: Annelids are segmented worms
All annelids (“little rings”) have segmented bodies. There are about 15,000 species ranging in length from less than 1 mm to 3 m for the giant Australian earthworm. Annelids live in the sea, most freshwater habitats, and damp soil. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

34 Annelids have a true coelom - which allows for easier fluid movement between organs
They have body segmentation - each segment can become specialized closed circulatory system with hearts- blood with hemoglobin excretory tubes called metanephridia collects wastes from the blood through a funnel called a nephrostome and dumps it outside through nephridia pores.


36 Fan Worm

37 Polychaete worm is an Annelid
they have true body segmentation they have parapodia used in locomotion and gas exchange


39 Until this century, leeches were frequently used by physicians for bloodletting.
Leeches are still used for treating bruised tissues and for stimulating the circulation of blood to fingers or toes that have been sewn back to hands or feet after accidents. Fig d Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings


41 Phylum Nematoda: Roundworms are nonsegmented pseudocoelomates covered by tough cuticles
complete digestive tract

42 Trichinella spiralis in pork muscle

43 In a true coelom, muscle entirely lines the wall of the body cavity allowing for efficient movement of material between organs and also movement along the length of the gut

44 BLASTULA invagination Forms mouth in protostomes GASTRULA NEURULA

45 Arthropods are segmented coelomates with exoskeletons and jointed appendages
The diversity and success of arthropods is largely due to three features: body segmentation, a hard exoskeleton, and jointed appendages.

46 Peripatus or Walking worm may be the predecessor of Arthropods
segmented but missing jointed appendages Phylum Onychophoran

47 Trilobita were segmented but most were the same
- modern arthropods have fewer and more specialized segments

48 Crustaceans

49 03/07/06 -- Divers have discovered a new crustacean in the South Pacific that resembles a lobster and is covered with what looks like silky, blond fur, French researchers said Tuesday. Scientists said the animal, which they named Kiwa hirsuta, was so distinct from other species that they created a new family and genus for it. A team of American-led divers found the animal in waters 2,300 meters (7,540 feet) deep at a site 1,500 kilometers (900 miles) south of Easter Island last year, according to Michel Segonzac of the French Institute for Sea Exploration

50 Chelicerata include a living fossil called the horseshoe crab

51 The whip scorpion like all chelicerates have
clawlike feeding appendages instead of mandibles (jaws) of insects they have no anntennae two body segments and simple eyes

52 Spiders have cheicerae - piercing mouth parts a pair of appendages called pedipalps used for sensing or feeding four pairs of walking legs book lungs used for gas exchange

53 A Centipede (Class Chilopoda) is molting its chitonous exoskeleton
one pair of legs per segment a pair of antennae poison claws at its anterior end

54 Millipede (Class Diploda)
two pairs of legs per segment herbivorous as opposed to the carnivorous centipedes

55 Flight is one key to the great success of insects.
Flying animals can escape many predators, find food and mates, and disperse to new habitats faster than organisms that must crawl on the ground. Many insects have one or two pairs of wings that emerge from the dorsal side of the thorax. Wings are extensions of the cuticle and are not true appendages. Fig Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

56 Insecta is the largest class
3 body parts with 3 pairs of legs two pair of wings nitrogenous waste excreted through Malpighian tubules gas exchange through tracheal tubes mandibles (jaws)

57 The internal anatomy of an insect includes several complex organ systems.
In the complete digestive system, there are regionally specialized organs with discrete functions. Metabolic wastes are removed from the hemolymph by Malpighian tubules, outpockets of the digestive tract. Respiration is accomplished by a branched, chitin-lined tracheal system that carries O2 from the spiracles directly to the cells. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

58 Butterflies undergo complete metamorphosis as opposed to grasshopper which undergo incomplete metamorphosis


60 Introduction echinoderms
At first glance, sea stars and other echinoderms would seem to have little in common with the phylum Chordata, which includes the vertebrates. However, these animals share the deuterostome characteristics of radial cleavage, development of the coelom from the archenteron, and the formation of the anus from the blastopore. These developmental features that define the Deuterostomia are supported by molecular systematics. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

61 Echinoderms Coelomates Deuterostomes Radial Symmetry
Echinoderms have water entering into a madreporite down a water vascular system that operates tube feet They are capable of everting their stomach through their mouth - either dumping the contents or digesting something outside of its body

62 Deuterostomes Mouth forms later (second) Forms ANUS first

63 They are capable of regeneration

64 Class Astroidea includes the
Sea Star Tiny skin gills are protected by spines and pincer like pedicillariae

65 Class Ophiuroidea includes the Brittle Stars

66 Class Echinoidea include the Sea Urchin and Sand Dollar

67 Class Crinoidea Sea Lillies most primitive of the living classes has changed little over time

68 Class Holothoroidea sea cucumbers lack spines hard endoskeleton is reduced



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