Chapter 13 - The Evolution And Diversity Of Animals

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bilateral symmetry

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a body plan in which the right and left sides of the body are mirror images of each other

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zoologists

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biologists who study animals

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phylum (pl. phyla)

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a major taxonomic group just below the kingdom level, comprising members of similar classes, all with the same general body plan; equivalent to the division in plants

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Porifera

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the phylum containing the sponges

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sessile

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in animals, the quality of being permanently attached to a fixed surface

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choanocytes

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cells that line the pores perforating the body wall of sponges; each cell has a flagellum that draws a current of water through the pore, and a sticky collar, which catches bacteria, protists, and other small organic particles suspended in the water; also called collar cells

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spicule

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a slender, spiky rod of silica or calcium carbonate found in sponges that supports the soft wall and provides some protection from predators

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Cnidaria

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the phylum containing animals with a radial body plan and nematocysts

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radial body plan

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a body with a central axis with structures radiating outward like spokes of a wheel

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epidermis

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the outer layer of cells of an organism

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mesoglea

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a jellylike substance lying between the epidermis and gastrodermis in cnidarians such as jellyfish

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polyp

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(L. palypus, many-footed the sedentary stage in the life cycle of cnidarians; a cylindrical organism with a whorl of tentacles surrounding a mouth at one end; sea anemones and hydras are examples of polyps living alone; corals are example of colonial polyps

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medusa

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(Gr. mythology, a female monster with snake-entwined hair) a jellyfish or the free-swimming stage in the life cycle of cnidarians; an inverted umbrella-shaped version of a polyp, with the mouth and tentacles pointing downward

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nematocyst

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a stinging capsule found in cnidarians, which, when stimulated, shoots out a tiny barb containing a poisonous substance that immobilizes or kills the prey or predator

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ctenophores

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the group of animals commonly known as comb jellies

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protostome

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(Gr. protos, first + stoma, mouth) any bilateral animal whose first opening in the embryo (blastopore) becomes the mouth, while the second opening becomes the anus; also characterized by spiral cleavage during development; includes annelids, mollusks, and arthropods

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deuterostome

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an animal whose first opening in the embryo (blastopore) becomes the anus, while the second opening to develop becomes the mouth; includes echinoderms and chordates

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coelom

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(Gr. koiloma, a hollow) the main body of cavity of many animals, formed between layers of mesoderm, in which internal organs are suspended

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zoology

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the study of animals

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lophophore

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specialized feeding tentacles possessed by one group of protostomes

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trochophore

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a specialized larval form that occurs among many protostome animals, including several kinds of worms and all of the mollusks

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Lophotrochozoans

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animals with a specialized feeding apparatus called a lophophore or a specialized larval form called a trochophore; the group includes several kinds of worms and all of the mollusks

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Ecdysozoa

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animals that form and shed a tough external skeleton; include the arthropods and nematodes

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flatworm

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a member of the phylum Platyhelminthes, the simplest animal group to display bilateral symmetry and cephalization

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planaria

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a group of flatworms that inhabit freshwater lakes, rivers, or bodies of salt water

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cephalization

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(Gr. kephale, head) a type of animal body plan or organization in which one end contains a nerve-rich region and functions as a head

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mesoderm

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the middle cell layer of an embryo; gives rise to muscles, bones, connective tissue, and reproductive and excretory organs

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acoelomate

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in animals, the condition of lacking a coelom

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Annelida

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the phylum containing the segmented worms, worms with tiny ringlike external segments

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segmented worm

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a member of the phylum Annelida

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mollusk

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a member of the phylum Mollusca; includes snails, slugs, clams, oysters, squid, and octopuses

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Mollusca

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the phylum containing the mollusks

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head

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the part of an animal that contains a major concentration of sense organs and generally encounters the environment first as the animal moves along

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foot

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the locomotive organ in mollusks

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mantle

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a thick fold of tissue found in mollusks that covers the visceral mass and that in some mollusks secretes the shell

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visceral mass

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most of the body of a mollusk, including the internal organs and excluding the foot and mantle

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radula

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a rasping organ in mollusks that shreds plant material by rubbing it against the hardened surface of the mouth

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gill

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[1] a specialized structure that exchanges gases in water-living animals; [2] the plates under the cap of certain fungi

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blood-filled cavity

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area within the body of a mollusk where internal organs and tissues are bathed by blood

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open circulatory system

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a system of fluid transport in spiders, insects, and many other invertebrates in which a clear blood equivalent called hemolymph circulates partially in vessels and partially unconfined by tubes or vessels

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gastropod

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a member of the class Gastropoda in the phylum Mollusca; includes snails, garden slugs, and sea slugs

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torsion

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an internal twisting of the body mass during embryonic development

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bivalve

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a mollusk whose body is enclosed within two valves or shells; includes mussels and clams

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filter feeders

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aquatic organisms with feeding structures that can strain out and collect tiny food particles suspended in water

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cephalopod

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a member of the class Cephalopoda, phylum Mollusca, including squids, octopuses, and the chambered nautilus

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siphon

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in certain mollusks, the funnel through which water passes in the mantle cavity

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Brachiopoda

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the animal phylum that contains the lamp shells

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roundworm

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a member of the phylum Nematoda

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Nematoda

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the animal phylum containing roundworms, Earth’s most abundant animals

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pseudocoelom

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a “false” body cavity only partially covered with mesoderm

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Arthropoda

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Earth’s largest phylum; member animals have legs with joints, an exoskeleton made of chitin, and specialized body segments including a head, thorax, and abdomen or a fused cephalothorax and abdomen

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arthropod

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a joint-legged animal, including insects, spiders, ticks, centipedes, lobsters, and crabs

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exoskeleton

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the thick cuticle of arthropods, made of chitin

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joint

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the hinge, or point of contact, between two bones

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thorax

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the central region of the body of an arthropod or vertebrate between the head and the abdomen

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abdomen

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the posterior part of an arthropod’s body; in vertebrates, the abdomen lies between the thorax and the pelvic girdle

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cephalothorax

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the fused head and thorax of many arthropods

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centipedes

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arthropods with a series of flattened body segments, each bearing a pair of jointed legs

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millipedes

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arthropods with a long series of body segments, each bearing two pairs of legs

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crustaceans

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arthropods with a protective shell and two pairs of antennae, including crabs, shrimp, and lobsters

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carapace

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the exoskeleton covering the cephalothorax of many arthropods; also refers to the tough outer coverings of the turtle and armadillo

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arachnids

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arthropods lacking antennae and usually have eight walking legs; includes the spiders, ticks, mites, and scorpions

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spinneret

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a tubular appendage in spiders and some insects that reels out silk threads

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insect

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a member of class Insecta; arthropods having three main parts (head, thorax, and abdomen), three pairs of legs, and generally two pairs of wings; the largest class of animals

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larva

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an immature form of an insect and many other animal types

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pupa

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insects with complete metamorphosis, the stage that intervenes between the larva and the adult; in some cases, as in moths, the pupa is encased inside a cocoon

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metamorphosis

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(Gr. meta, after + morphe, form + osis, state of) the process in which there is a marked change in morphology during postembryonic development; in insects, the change in body form that takes place as the individual changes from a larva, such as a caterpillar, and emerges as an adult, such as a butterfly; in amphibians, the change from a tadpole to a frog

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social insect

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a member of any of the insect groups, such as ants, bees, and termites, that lives in colonies of related individuals and exhibits complex social behaviors

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castes

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subgroups of social insects that differ in appearance and behavior

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Echinodermata

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a phylum that includes “spiny-skinned” animals like the sea stars, brittle stars, sea urchins, and sea cucumbers

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endoskeleton

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(Gr. endos, within + skeletos, hard) an internal supporting structure, such as the bony skeleton of a vertebrate

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water vascular system

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in echinoderms, a system of fluid-filled canals that includes hundreds of short branches called tube feet that can attach to objects and thus aid in locomotion or feeding

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Hemichordata

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a phylum that includes the acorn worms

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Chordata

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a phylum that includes animals with a notochord and, often, a vertebral column

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vertebral column

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the backbone

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vertebrate

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an animal that possesses a vertebral column, or backbone

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notochord

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a rod of mesodermal cells in the chordate embryo that marks the location of the backbone in vertebrates

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spinal cord

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a tribe of nerve tissue that runs the length of a vertebrate animal, just above (dorsal to) the notochord

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gill slits

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in chordates, pairs of openings through the pharynx to the exterior

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pharynx

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[1] in vertebrates, a tube leading from the nose and mouth to the larynx and esophagus; conducts air during breathing and food during swallowing; the throat; [2] in flatworms, a short tube connecting the mouth and intestine

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myomeres

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blocks of embryonic or larval animal tissue that generate the muscles and bones

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Urochordata

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the subphylum containing the sea squirts, which, as larvae, have the five features characteristic of chordates

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Cephalochordata

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the subphylum containing the lancelets or amphioxus which, as adults, have the five characteristics of chordates

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Vertebrata

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the subphylum containing the vertebrates or animals with vertebral columns

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lancelet

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a cephalochordate that lives as a small, streamlined, fishlike marine animal half-buried in sand

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agnathan

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jawless fish

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jawless fish

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fish that lacked hinged jaws; agnathans

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jawed fish

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fish with hinged jaws

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placoderm

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the ancient group of armor-plated fishes that gave rise to the modern fishes

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cartilaginous fish

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fish whose skull, vertebrae, and other skeletal parts are made of cartilage instead of bone; includes skates and rays

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bony fish

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fish whose skeleton contains bone

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lobe-finned fish

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a member of the oldest of the groups of bony fishes; includes lungfishes and coelacanths

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lungfish

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an air-breathing lobe-finned fish having a lunglike air bladder in addition to gills

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coelacanth

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a type of lobe-finned fish

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ray-finned fish

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fish whose fins are made of webs of skin over rays of bones

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teleost

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a modern bony fish; includes most living fish and characterized by the presence of a swim bladder and spiny fins

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amphibian

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a cold-blooded vertebrate that starts life as an aquatic larva, breathing through gills, and metamorphoses into an air-breathing adult; includes frogs, toads, newts, and salamanders

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reptile

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a cold-blooded, scaly, lung-breathing vertebrate that lays large eggs that usually have a shell; the dominant group of animals in the Mesozoic era; includes crocodiles, lizards, tortoises, and birds

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amniote eggs

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eggs that encase an embryo in an amnion surrounding a pool of fluid and contain a yolk

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thecodonts

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small, extinct lizards that ran on two legs and gave rise to the dinosaurs

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therapsid

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an extinct lineage of fierce, heavyset reptiles that gave rise to the mammals

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dinosaur

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an extinct giant reptile; the dominant form of land vertebrate during the Jurassic and Cretaceous periods

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birds

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winged vertebrates with feathers, air sacs, and a four-chambered heart

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feather

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a flat, light, waterproof epidermal structure on a bird; collectively functions as insulation and for flight

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homeothermic

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“warm-blooded”; able to maintain a constant internal body temperature

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air sac

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a thin-walled extension of the lungs; in birds, air flows through lungs and air sacs during respiration

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four-chambered heart

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a heart with four chambers that completely separates oxygenated and deoxygenated blood

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mammal

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a vertebrate animal of the class Mammalia, having the body generally covered with hair, nourishing young with milk from mammary glands, and generally giving birth to live young; includes lions, whales, rabbits, and kangaroos

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milk

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a fluid rich in fats and proteins produced in the mammary glands of mammals that nourishes newborns

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mammary gland

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gland that produces milk in mammals

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fur

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a body covering of hair

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blubber

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a thick layer of fat acting as insulation in such mammals as whales, porpoises, and seals

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placenta

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in mammals, the spongy organ rich in blood vessels by which the developing embryo receives nourishment from the mother

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monotreme

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an egg-laying mammal that slo has many primitive or reptilian features; the only living forms are the spiny anteater and the duck-billed platypus

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marsupial

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a mammal having a pouch in which it carries its young, which are born in a small and undeveloped state; found extensively in Australia, with a few representatives in America; include kangaroos, possums, and koala bears

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marsupium

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an elastic pouch of skin that harbors newborn marsupials

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Primata

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the mammalian order including monkeys, apes, and humans

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Homo Sapiens

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the genus and species of modern humans

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Strepsirhini

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a suborder of mostly tree-dwelling primates including the lemurs and lorises

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Haplorhini

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a suborder of primates including the tarsiers and the anthropoids―the New World monkeys, Old World monkeys, apes, and humans

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anthropoid

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a member of the suborder Anthropoides, order Primata; includes humans, apes, and New and Old World monkeys

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New World monkeys

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primates with prehensile tails that live in the forests of Southern Mexico and Central and South America

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prehensile

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grasping (as in the tails of some species of monkeys)

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Old World monkeys

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monkeys lacking prehensile tails that live in Africa, India, and Southeast Asia

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hominoids

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the primate group including the apes and humans

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opposable thumb

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a first digit or thumb that can be held opposite the other digits; characteristic feature of some primates

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bipedal

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walking consistently on two legs

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stereoscopic vision

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depth perception based on the orientation of the eyes and their brain connection

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great ape

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a lineage of animals that includes the orangutans, the gorillas, the humans, and two species of chimpanzees (the common chimp and the bonobo)

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Homo Erectus

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“erect human” species that evolved by 1.8 million years ago, used tools, and spread into northern Africa