Invertebrates

Important words and concepts from Chapter 33, Campbell & Reece, 2002 (5/12/2003):

by Stephen T. Abedon (abedon.1@osu.edu) for Biology 113 at the Ohio State University

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Vocabulary words are found below

(1) Chapter title: Invertebrates

(a) [invertebrates (Google Search)] [index]

(2) Invertebrates

(a) This chapter surveys the invertebrate animals

(b) Most animal phyla are invertebrates (in fact, all animal phyla but one contain nothing but invertebrates)

(d) In our survey of the invertebrates we will consider only 10 of these (those not considered here but considered by your text are in parentheses and are linked to a Google Search)

(i) Porifera

(ii) Cnidaria

(iii) (Ctenophora)

(iv) Platyhelminthes

(v) Rotifera

(vi) Nematoda

(vii) (Nemertea)

(viii) (Bryozoa)

(ix) (Phoronida)

(x) (Brachiopoda)

(xi) Mollusca

(xii) Annelida

(xiii) Arthropoda (actually perhaps better classified as a “superphylum” containing at least four phyla)

(xiv) Echinodermata

(xv) Chordata

(e) See Figure 32.4, A traditional view of animal diversity based on body-plan grades (for an overview of invertebrate relationships and characteristics)

(f) As discussed in the previous chapter, these phyla may be grouped according to their adult and embryological forms into

(i) Parazoa vs. Eumetazoa

(ii) Radiata vs. Bilateria

(iii) Diploblastic vs. Triploblastic

(iv) Acoelomates vs. Pseudocoelomates vs. Coelomates

(v) Protostomes vs. Deuterostomes

(g) See Table 33.7, Animal phyla

(h) Note that while common names are important, when one formally asks for a taxon (e.g., phylum, order, class, etc. as an exam question) one expects a formal taxon as a reply (e.g., phylum Cnidaria rather than jellyfish)

(i) [invertebrates (Google Search)] [index]

PHYLYM PORIFERA (SPONGES)

(3) Phylum Porifera (sponges, amoebocyte, choanocyte)

(a) Poriferans are considered to be the only members of the Parazoa (versus eumetazoa) split

(b) Phylum Porifera includes the sponges

(i) Lack true tissues

(ii) Are the simplest of Animals

(iii) Have no nerves or muscles (though they are capable of responding, as individual cells, to their environments)

(iv) Possess choanocytes (collar cells) which are “unique flagellated cells that ingest bacteria and tiny food particles” (p. 675, Campbell & Reece, 2002); (choanocytes look a lot like choanoflagellates)

(v) Possess amoebocytes, a type of cell that transfers food to rest of the sponge cells

(vi) Are sessile as adults but are non-sessile as larvae (juvenile form)

(vii) Sponge “cells tend to be totipotent (retain zygote’s ability to form the whole animal)” (p. 675, Campbell & Reece, 2002)

(d) "Sponges are among the least complex of all animals. They lack organs, and the cell layers are loose federations of cells, not really tissues because the cells are relatively unspecialized. Sponges have no nerves or muscles, but the individual cells can sense and react to changes in the environment."

(e) “The body of a simple sponge resembles a sac perforated with holes (Porifera means pore bearer). Water is drawn through the pores into a central cavity…, then flows out of the sponge through a larger opening… Under certain conditions the cells around the pores [and larger opening] contract, closing the openings.” (p. 648, Campbell & Reece, 2002)

(f) “Nearly all sponges are suspension-feeders (also known as filter feeders), which are animals that collect food particles from water passed through some type of food-trapping equipment.” (p. 649, Campbell & Reece, 2002)

(i) (note, however, that there are some sponges that are, in fact, carnivorous, trapping and then consuming animals such as crustaceans)

(g) Sponges feed by using flagellated cells (choanocytes) to move water through their bodies

(h) Food particles are trapped by collared and flagellated cells (also the choanocytes) and are then phagocytized

(i) These food particles are transferred to cells with mobile, amoeboid morphology called amoebocytes, which digest food and then make the digestive products available to the rest of the sponge cells

(j) Though sessile (i.e., anchored in place to the sea bottom), sponges produce non-sessile larvae that allow the sponges to disseminate to new locals

(k) See Figure 33.2, A sponge

(l) See Figure 33.3, Anatomy of a sponge

(m) [phylum Porifera, sponges, amoebocyte, choanocyte, amoebocyte and sponges (Google Search)] [index]

PHYLYM CNIDARIA (JELLIS, CORALS, ETC.)

(4) Phylum Cnidaria (medusa, polyp, cnidocytes, coral polyps, hydra, jellyfish, sea anemone)

(a) Phylum Cnidaria includes the hydra, jellyfish, sea anemones, and coral polyps

(b) See Figure 33.6, Representatives of the cnidarian classes

(d) Cnidarians have only a single opening to their digestive cavity; i.e., they don’t have a gut

(e) See Figure 33.4, Polyp and medusa forms of cnidarians

(f) They are carnivores, i.e., they eat other, living animals, employing cells called cnidocyotes to sting and grasp their prey

(g) See Figure 33.5, A cnidocyte of a hydra

(h) Cnidarians possess simple nervous systems as well as muscles (though the latter are not considered true muscles since true muscles are derived from mesodermal tissue and Cnidarians lack mesodermal tissue, i.e., they are diploblastic)

(i) Cnidarians exist as either sessile polyps or as floating medusa; some Cnidarians switch back and forth between the two body plans while others exist as either one body plan or the other

(j) See Figure 33.7, The life cycle of the hydrozoan Obelia

(k) Polyps are cylindrical, adhere to substratum and expose their mouth/anus to the water where their tentacles serve to snare food, e.g., hydra and sea anemones

(l) These are polyps:

(m) Medusa are flattened (pancake-like) and have their mouth hanging beneath their bodies, also employing their tentacles to snare food, e.g., jellyfish

(n) This is a medusa:

(o) See Figure 33.4, Polyp and medusa forms of cnidarians

(p) [phylum Cnidaria, cnidarians, medusa and cnidaria, polyp and cnidaria, class Anthozoa, coral polyp, sea anemone, class Hydrozoa, hydra and cnidaria, class Scyphozoa, jellyfish (Google Search)] [index]

PHYLYM PLATYHELMINTHES (FLATWORMS)

(5) Phylum Platyhelminthes (flatworms, flukes, tapeworms)

(a) Phylum Platyhelminthes includes the flatworms (which, as parasitic flatworms, are known as flukes and tapeworms)

(b) Platyhelminthes live in water or damp environments

(c) See Figure 33.9, A flatworm

(d) See Figure 33.10, Anatomy of a planarian

(e) Platyhelminthes are bilaterally symmetrical acoelomates

(f) The digestive cavity of flatworms possesses only a single opening

(g) Platyhelminthes lack a circulatory system

(h) They are able to diffuse oxygen and wastes to their body cells; this is possible because of the short distances within their bodies afforded by their very flat shape and the branching nature of their digestive cavity

(i) "The flat shape of the body (of the flatworm) places all cells close to the surrounding water, and fine branching of the gastrovascular cavity (i.e., serving as both digestive cavity and circulatory system) distributes food throughout the animal."

(j) Flatworms move by employing cilia found on their ventral (bottom) surface

(k) "A planarian has a head (is cephalized) with a pair of eyespots that detect light and lateral flaps that function mainly for smell. The planarian nervous system is more complex and centralized than the nerve nets of cnidarians. Planarians can learn to modify their responses to stimuli."

(l) The flukes and tapeworms are parasitic Platyhelminthes

(m) See Figure 33.12, Anatomy of a tapeworm

(n) [phylum Platyhelminthes, platyhelminths, class Cestoidea, tapeworms, class Monogenea, class Trematoda, flukes, flukes and platyhelminthes, class Turbellaria, flatworms (Google Search)] [index]

PHYLYM ROTIFERA

(6) Phylum Rotifera

(a) Phylum Rotifera includes the rotifers

(b) Rotifers are extremely small animals and possess a pseudocoelom

(d) Rotifers fill a niche somewhat similar to that of a large, engulfing protozoa

(e) "Internal organs lie within the pseudocoelom. The fluid that fills the pseudocoelom serves as a hydrostatic skeleton and as a medium for the internal transport of nutrients and wastes."

(f) Diagram of a rotifer:

(g) See Figure 33.13, A rotifer

(h) [Rotifera, rotifers (Google Search)] [index]

PHYLYM NEMATODA

(7) Phylum Nematoda (roundworms)

(a) Phylum Nematoda are the round worms

(b) "Roundworms are among the most numerous of all animals in both species and individuals."

(d) Parasitic roundworms include the pinworms and hookworms

(e) "They have a complete digestive tract, and the pseudocoelom with its fluid serves as a blood vascular system that transports nutrients throughout the body."

(f) “Though the ecdysozoans are considered a clade based mainly on the data of molecular systematics, this branch of protosomes is named for a characteristic life history: ecdysis, the shedding of an exoskeleton outgrown by the animal. Of the several ecdysozoan phyla, we will examine only the nematodes and the arthropods… [speaking of the former…] A tough exoskeleton called cuticle covers the body; as the worm grows, it periodically sheds its old cuticle (molting, or ecdysis) and secretes a new, larger one.” (p. 661, Campbell & Reece, 2002)

(g) See Figure 33.25, Nematodes

(h) [phylum Nematoda, nematodes, roundworms, pinworms, hookworms (Google Search)] [index]

PHYLYM MOLLUSCA

(8) Phylum Mollusca (mollusks, foot, mantle, visceral mass)

(a) Phylum Mollusca includes the mollusks

(b) Mollusks are Protostomes

(d) Most mollusks possess a calcium carbonate shell, though such things as squids, octopuses, and slugs partially or completely lack a shell (for a mollusk a lack of a shell is a derived character)

(e) The circulatory system of most mollusks is an open one; that is, the heart pumps vascular fluid (hemolymph) to the tissues through vessels, but there are no vessels in which the hemolymph returns to the heart; instead the blood returns by moving through the space between cells

(f) "Despite their apparent differences, all mollusks have a similar body plan. The body has three main parts:

(i) a muscular foot, usually used for movement;

(ii) a visceral mass, containing most of the internal organs; and

(iii) a mantle, a heavy fold of tissue that drapes over the visceral mass and may secrete a shell."

(g) See Figure 33.16, The basic body plan of mollusks

(h) [phylum Mollusca, mollusks, visceral mass, class polyplacotora [check spelling] (Google Search)] [images: mollusks (Australian Museum Online)] [images: mollusks (Molluscan Pictures)] [glossary of molluscan terminology] [mollusk larva home page] [phylum mollusca] [index]

(9) Class Gastropoda (snails, slugs, sea slugs)

(a) These are the snails, slugs, and sea slugs

(b) Gastropoda is the largest class of phylum Mollusca

(d) See Figure 33.19, Gastropods

(e) [class Gastropoda, gastropods, snails, slugs, sea slugs, slugs and gastropods (Google Search)] [index]

(10) Class Bivalvia (clams, muscles, scallops)

(a) These are the clams, muscles, scallops, i.e., the mollusks possessing hinged shells that divided into two halves

(b) See Figure 33.21, Anatomy of a clam

(d) See Figure 33.20, A bivalve

(e) [class Bivalvia, bivalves, clams, scallops (Google Search)] [index]

(11) Class Cephalopoda (octopuses, squids, chambered nautilus)

(a) Cephalopods are carnivorous mollusks

(b) Included in class Cephalopoda are the octopuses, the squids, and the chambered nautilus

(c) See Figure 33.22, Cephalopods

(d) All but the chambered nautilus possess either reduced shells (e.g., squids) or no shell at all (octopuses)

(e) Cepholods include the largest invertebrates, as well as the brightest (i.e., smartest), and also possess a closed circulatory systems

(f) [Cephalopoda, cephalopods, octopuses, squids, chambered nautilus, cuttlefish, ammonites (extinct shelled cephalopods) (Google Search)] [index]

(12) Closed circulatory system

(a) A closed circulatory system is one in which blood flows throughout an animal entirely within a series of tubes

(b) In particular, there are tubes that carry the blood back to the heart as well as the typically found tubes that carry blood away from the heart

(d) We have a closed circulatory system

(e) [closed circulatory system (Google Search)] [index]

PHYLYM ANNELIDA (SEGMENTED WORMS)

(13) Phylum Annelida (segmented worms)

(a) Phylum Annelida includes the segmented worms

(b) The segmented worms live in moist and wet environments

(d) These worms, of course, are also segmented

(e) In addition, they possess a closed circulatory system

(f) Various classes make up the annelids including (no need to memorize formal names of these taxa): (supplemental discussion)

(i) Oligochaeta (earthworms)

(ii) Polychaeta (marine worms)

(iii) Hirudinea (leeches)

(g) See Figure 33.23, Anatomy of an earthworm

(h) [Annelida, annelids, segmented worms (Google Search)] [index]

(14) Class Oligochaeta (earthworms) (supplemental discussion)

(a) The earthworms

(b) See Figure 33.23, Anatomy of an earthworm

(15) Class Polychaeta (marine worms) (supplemental discussion)

(a) The marine worms

(b) See Figure 33.24a, Annelids, the segmented worms

(16) Class Hirudinea (leeches) (supplemental discussion)

(a) The leeches

(b) These are predatory bloodsucking Annelid worms

(c) See Figure 33.24c, Annelids, the segmented worms

(d) [class Hirudinea, leeches (Google Search)] [index]

(SUPER)PHYLYM ARTHROPODA (INSECTS, ETC.)

(17) Phylum Arthropoda (superphylum Arthropoda)

(a) "On the criteria of species diversity, distribution, and sheer numbers, Arthropoda must be regarded as the most successful phylum of animals ever to live."

(b) Defining characteristics of arthropods include

(i) Segmentation

(ii) Hard exoskeletons

(iii) Jointed appendages

(iv) Cephalization

(v) Well-developed sensory organs

(vi) An open circulatory system

(c) See Figure 33.26, External anatomy of an arthropod

(d) The arthropods may actually be divided into four separate (though related) phyla all contained within a “superphylum” called Arthropoda:

(i) Phylum Trilobita (trilobites)

(ii) Phylum Chelicerata (chilicerates)

(iii) Phylum Uniramia (uniramians)

(iv) Phylum Crustacea (crustaceans)

(e) [Taxonomists traditionally grouped all the arthropods in one phylum, the phylum Arthropoda. Table 33.5, page 664, lists a few of the major arthropod classes in the context of this one-phylum tradition. However, many zoologists now prefer to split the arthropods into multiple phyla corresponding ot the four great lineages: phylum Trilobita, phylum Chelicerata, phylum Uniramia, phylum Crustacea. This trend toward splitting former taxa into a larger number of new ones, based mainly on cladistic analysis, extends to lower taxa. For example, many systemicists now split what was the uniramian calss Insecta into several classes. And there are other modern taxonomic issues. For instance, some systematists now question whether Uniramia is a monophyletic clade. These scientists interpret the molecular and anaotomical data used to construct cladograms to mean that insects are actually more closely related to crustaceans than they are to centipedes and millipedes. ¶ As we have seen throughout our survey of the diversity of life, systematics, and the taxonomy it informs, is currently one of the most vibrant fields of biology. We do want you to be aware that phylogenetic trees and classifications represent hypotheses about the history of life that are presently being reconstructed in light of molecular data and other new approaches. However we don’t want the current taxonomic turmoil to detract from your appreciation of life’s diverse forms. The following survey of arthropods showcases a few major groups, which can be variously classified as phyla, subphyla or classes, dependeing on the taxonomic scheme.” (pp. 663-664, Campbell & Reece, 2002)]

(f) [phylum Arthropoda, superphylum Arthropoda, arthropods (Google Search)] [index]

(18) Segmentation

(a) The arthropods are segmented like the annelid worms

(b) It is uncertain, however, whether this common segmentation represents an analogy or instead a homology (i.e., whether the common ancestor to both phyla possessed segmentation)

(c) See Figure 33.36, Three hypotheses for the origin of segmentation

(d) [segmentation and arthropods (Google Search)] [index]

(19) Exoskeleton (cuticle)

(a) The arthropods possess a hard exoskeleton (cuticle) consisting of chitin and protein plus varying degrees of mineralization

(b) Varying thickness controls the degree of flexibility versus rigidity displayed by the exoskeleton in various locations within the same animal

(i) Muscle attachment point (to the inside)

(ii) Protection/armor

(iii) Support out of buoyant environments (i.e., in air)

(iv) Water impermeability

(d) These latter two properties probably served as preadaptations to terrestrial living

(e) As they grow, arthropods must periodically molt (lose/shed their exoskeleton) and then reform their exoskeleton

(f) [exoskeleton (Google Search)] [index]

(20) Jointed appendages

(a) Appendages of arthropods are associated with body segments

(b) Appendages can include such things as

(i) Antennae

(ii) Mouth parts

(iii) Claws

(iv) Legs

(v) Swimming appendages

(d) See Figure 33.26, External anatomy of an arthropod

(e) [jointed appendages (Google Search)] [index]

(21) Cephalization

(a) Arthropods typically have highly sophisticated heads possessing numerous appendages, sensory organs, their brain, and their mouth

(b) [cephalization (Google Search)] [index]

(22) Sensory organs

(a) Arthropods tend to possess eyes, ears, olfaction (sense of smell), touch, etc.

(b) [(Google Search)] [index]

(23) Open circulatory system (hemolymph)

(a) The circulatory system of arthropods consists of a heart, arteries, but no veins

(b) That is, the circulatory fluid is not returned to the heart through vessels, but instead passes through body spaces (sinuses) surrounding tissue as does our own lymph

(c) Such fluid, instead of being called blood, is given the name hemolymph (i.e., a hybrid between the hemoglobin-carrying blood and the within-tissues-flowing lymph)

(d) [open circulatory system, hemolymph (Google Search)] [index]

(24) Phylum Trilobita (trilobites) (Subphylum Trilobitomorpha)

(a) The trilobites were fairly simple, aquatic arthropods

(b) The trilobites did not survive the Permian extinction (250 million years ago)

(c)

(d) See Figure 33.27, A trilobite arthropod

(e) [subphylum Trilobitomorpha, trilobites (Google Search)] [among my trilobites (remarkable images of trilobites that simply have to be seen to be believed) (The Galef Oceanside Asylum)] [index]

(25) Phylum Chelicerata (cephalothorax, abdomen, scorpions, spiders, mites, ticks, horseshoe crabs) (Subphylum Cheliceriformes)

(a) The chelicerates have bodies divided into an anterior cephalothorax and a posterior abdomen

(b) The chelicerates possess more sophisticated appendages than did the trilobites

(d) The chelicerates possess feeding appendages called chelicerae (contrast with the uniramians and crustaceans which both instead posses mandibles)

(e) Modern chelicerates include

(i) Scorpions

(ii) Spiders

(iii) Mites

(iv) Ticks

(v) Horseshoe crabs (a marine chelicerate)

(f) See Figure 33.28, The horseshoe crab (Limulus polyphemus)

(g) See Figure 33.29, Arachnids

(h) See Figure 33.30, Spiders (Class Arachnida)

(i) [subphylum Cheliceriformes, cephalothorax, chelicerae, scorpions, spiders, mites, ticks, horseshoe crabs (Google Search)] [index]

(26) Phylum Uniramia (Subphylum Uniramia)

(a) The uniramians are a (likely terrestrially evolved) phylum of superphylum Arthropoda (or subphylum of phylum Arthropoda; but which, according to your text, in either case may very well be polyphyletic)

(b) The uniramians includes (or, at least, has included)

(i) Millipedes (class Diplopoda)

(ii) Centipedes (class Chilopoda)

(iii) Insects (class Insecta)

(c) [note that above I am retaining the class designation for these groups; this is a bit of a cheat since by calling the Uniramia a phylum I should also be calling the above class designations subphyla as in subphylum Diplopoda, subphylum Chilopoda, and subphylum Insecta]

(d) [“Developing evidence from developmental genetics and nucleic acid sequencing challenges the uniramia grouping and supports a somewhat different view of arthropod classification and phylogeny. Insects and crustaceans may be more closely related than traditionally thought; in fact, they may constitute a monophyletic group distinct from the millipedes and centipedes.” (p. 616, Campbell et al., 1999)]

(e) [subphylum Uniramia (Google Search)] [index]

(27) Class Diplopoda (millipedes)

(a) These are the millipedes

(b) Millipedes

(i) Possess numerous segments

(ii) Possess two-pairs of walking legs per segment

(iii) Are herbivores (eat plants)

(c) See Figure 33.31a, Class Diplopoda (millipedes) and Class Chilopoda (centipedes)

(d) [class Diplopoda, millipedes (Google Search)] [index]

(28) Class Chilopoda (centipedes)

(a) These are the centipedes

(b) Centipedes possess

(i) Fewer segments than millipedes

(ii) One pair of walking legs per segment

(iii) Are carnivorous

(iv) Possess more specialized appendages

(c) See Figure 33.31b, Class Diplopoda (millipedes) and Class Chilopoda (centipedes)

(d) [class Chilopoda, centipedes (Google Search)] [index]

(29) Class Insecta (insects, thorax, abdomen)

(a) "In species diversity, insects (class Insecta) outnumber all other forms of life combined."

(b) Insects possess

(i) 0, 2, or 4 wings, which consist of modified cuticle (i.e., exoskeleton)

(1) See Figure 33.32, Insect flight

(ii) A head (anterior segment), thorax (middle segment), and abdomen (posterior segment)

(iii) Six legs

(iv) Gas exchange based on trachea

(v) Metamorphosis (incomplete or complete)

(c) See Table 33.6, Major Orders of Insects

(d) See Figure 33.33, Anatomy of a grasshopper, an insect

(e) [class Insecta, insects, thorax, abdomen, insect head, insect thorax, insect abdomen (Google Search)] [index]

(f) The following is summary of insect orders (no need to memorize):

(i) [lice, order Anoplura (Google Search)]

(ii) [beetles, order Coleotera (Google Search)]

(iii) [Earwigs, order Dermaptera (Google Search)]

(iv) [flies, mosquitoes, order Diptera (Google Search)]

(v) [true bugs, assassin bug, bedbug, chinch bug, order Hemiptera (Google Search)]

(vi) [ants, bees, wasps, order Hymenoptera (Google Search)]

(vii) [termites, order Isoptera (Google Search)]

(viii) [butterflies, moths, order Lepidoptera (Google Search)]

(ix) [damselflies, dragon flies, order Odonata (Google Search)]

(x) [crickets, roaches, grasshoppers, mantids, order Orthoptera (Google Search)]

(xi) [fleas, order Siphonaptera (Google Search)]

(xii) [caddisflies, order Trichoptera (Google Search)]

(30) Trachea

(a) Trachea are branched tubes that go from the outer surface of the cuticle, inward to bring body cells in direct contact with the atmosphere

(b) In other words, insects have gas exchange organs all over the surface of their bodies

(c) [“Insect trachea are a network of tiny tubes that go throughout the insect's body. These tubes connect each cell of the body to the outside, through holes in the abdomen (the tail section) called spiracles. Insects don't get their oxygen with lungs like we do. Instead, their tracheal system allows each cell in the insect's body to get oxygen directly from the outside air. Air can go in through the spiracles, travel through the tracheal tubes, and go right to each cell. ¶ Since oxygen can get from the air to the insect's cells directly, insects don't need to carry oxygen in their blood like we do! That's why insect blood isn't red: because it doesn't have the oxygen-carrying molecules that make human blood red.” (Comparative Anatomy) Note that you are looking at hollow branched tubes that penetrate into the insects body]

(d) [trachea and insect (Google Search)] [index]

(31) Metamorphosis (complete metamorphosis, incomplete metamorphosis)

(a) Many insects possess two very different-looking morphologies when they are young versus when they are older

(b) The younger morphology looks a lot like a segmented worm (i.e., the maggot/grub/caterpillar stage)

(c) The generally somewhat abrupt transition from the juvenile morphology to the adult morphology is known as "complete metamorphosis"

(d) See Figure 33.34, Metamorphosis of a butterfly

(e) A more gradual change from a more adult-like juvenile state to a larger adult morphology is known as "incomplete metamorphosis"

(f) [“Cockroaches and grasshoppers, among many, go through incomplete metamorphosis. When cockroaches and grasshoppers hatch, they look like tiny replicas of their parents except for two important differences: They cannot reproduce yet and they lack functional wings. At this stage, they are called nymphs. The stage preceding each molt is known as an instar. Every time the nymph molts or sheds its exoskeleton, small changes take place, until the last molt is accomplished and the insect emerges as a winged adult. ¶ Another type of incomplete metamorphosis takes place in the lives of dragonflies and damselflies. These insects lay their eggs in water. After hatching, the immature offspring, who are known as "naiads," are aquatic. Unlike cockroach and grasshopper nymphs, they do not look at all like their terrestrial parents. However, like cockroach and grasshopper nymphs, naiads do not go through the pupal growth stage. They molt and gradually develop wings and reproductive organs as they increase in size.” (Letsfindout.com)]

(g) [metamorphosis, complete metamorphosis, incomplete metamorphosis (Google Search)] [index]

(32) Phylum Crustacea (lobsters, shrimp, crayfish, crabs, barnacles) (Subphylum Crustacea)

(a) The crustaceans are the most successful of the extant marine arthropods

(b) Many examples possess "gobs" of sophisticated appendages (e.g., 19 pairs for lobsters and crayfish including multiple examples of antennae, mouthparts, legs, and swimming appendages, on a single animal!)

(i) Lobsters (a decapod)

(ii) Shrimp (a decapod)

(iii) Crayfish (a decapod)

(iv) Crabs (a decapod)

(v) Barnacles

(vi) Plus various planktonic (including both krill and copepods) and terrestrial species (e.g., pill bugs and sow bugs, both isopods)

(d) See Figure 33.35, Crustaceans

(e) [subphylum Crustacea, crustaceans, lobsters, shrimp, crayfish, crabs, decapods, barnacles, krill, copepods, pill bugs, sow bugs, isopods (Google Search)] [index]

THE DEUTEROSTOMES (STARFISH & US)

(33) Phylum Echinodermata (sea stars)

(a) These are radially symmetrical animals possessing bilaterally symmetrical larvae; the inference is that the radial symmetry is a derived trait

(b) The most commonly known example of the echinoderms are the sea stars (starfish)

(i) Multiple arms (upon which in many are tube feet)

(ii) A water vascular system (provides the suction to the tube feet)

(iii) Tube feet:

(iv) A calciferous endoskeleton (note endo-, not exo-)

(d) See Figure 33.38, Anatomy of a sea star

(e) Unlike the rest of the coelomates discussed above, echinoderms are deuterostomes, i.e., their mouth is the derived opening to the digestive tract, not their anus

(i) (mouth/anus came first, then mouth, leaving the former mouth/anus as the anus; in protostomes it is the anus that came next leaving the former mouth/anus as the mouth)

(f) See Figure 33.37, Echinoderms

(g) As deuterostomes, the echinoderms are considered to be the invertebrate phyla most closely affiliated with the chordates, e.g., us

(h) [suphylum Echinodermata, echinoderms, sea stars, water vascular system [need to include google searches for the various echinodermata classes] (Google Search)] [index]