Bio Exam 4 Vocabulary

Animal Diversity

Acoelomate

animal without a body cavity

Bilateral Symmetry

type of symmetry in which there is only one plane of symmetry, so the left and right halves of an animal are mirror images

Blastopore

opening into the archenteron that forms during gastrulation

Blastula

16-32 cell stages of development of an animal embryo

Body Plan

morphology or defining shape of an organism

Cambrian Explosion

time during the Cambrian period (542 - 488 million years ago) when most of the animal phyla in existence today evolved

Cleavage

Cell divisions subdividing a fertilized egg (zygote) to form a multicellular embryo

Coelom

Lined body cavity

Cryogenian Period

Geologic period (850 - 630 million years ago) characterized by a very cold global climate

Determinate Cleavage

cleavage pattern in which developmental fate of each blastomere is tightly defined

Deuterostome

Blastopore develops into the anus, with the second opening developing into the mouth

Diploblast

animal that develops from two germ layers

Ecdysozoa

clade of protostomes that exhibit exoskeletal molting (ecdysis)

Ediacaran Period

geological period (630 - 542 million years ago) when the oldest definite multicellular organisms with tissues evolved

Enterocoely

mesoderm of deuterostomes develops as pouches that are pinched off from endodermal tissue, cavity contained within the pouches becomes coelom

Eucoelomate

animal with a body cavity completely lined with mesodermal tissue

Eumetazoa

group of animals with true differentiated tissues

Gastrula

stage of animal development characterized by the formation of the digestive cavity

Germ Layer

collection of cells formed during embryogenesis that will give rise to future body tissues, more pronounced in vertebrate embryogenesis

Hox Gene

(also, homeobox gene) master control gene that can turn on or off large numbers of other genes during embryogenesis

Indeterminate Cleavage

cleavage pattern in which individual blastomeres have the character of “stem cells,” and are not yet predetermined to develop into specific cell types

Lophotrochozoa

clade of protostomes that exhibit a trochophore larvae stage or a lophophore feeding structure

Mass Extinction

event or environmental condition that wipes out the majority of species within a relatively short geological time period

Metazoa

group containing all animals

Organogenesis

formation of organs in animal embryogenesis

Parazoa

group of animals without true differentiated tissues

Protostome

blastopore develops into the mouth of protostomes, with the second opening developing into the anus

Pseudocoelomate

animal with a body cavity located between the mesoderm and endoderm

Radial Cleavage

cleavage axes are parallel or perpendicular to the polar axis, resulting in the alignment of cells between the two poles

Radial Symmetry

type of symmetry with multiple planes of symmetry, with body parts (rays) arranges around a central disk

Schizocoely

during development of protostomes, a solid mass of mesoderm splits apart and forms the hollow opening of the coelom

Spiral Cleavage

cells of one pole of the embryo are rotated or misaligned with respect to the cells of the opposite pole

Troploblast

animal that develops from three germ layers

Amoebocyte

sponge cell with multiple functions, including nutrient delivery, egg formation, sperm delivery, and cell differentiation

Annelida

phylum of vermiform animals with metamerism

Archenteron

primitive gut cavity within the gastrula that opens outward via the blastopore

Arthropoda

phylum of animals with jointed appendages

Biramous

referring to two branches per appendage

Captacula

tentacle-like projection that is present in tusks shells to catch prey

Cephalothorax

fused head and thorax in some species

Chelicera

modified first pair of appendages in subphylum Chelicerata

Choanocyte

(also, collar cell) sponge cell that functions to generate a water current and to trap and ingest food particles via phagocytosis

Chordata

phylum of animals distinguished by their possession of a notochord, a dorsal, hollow nerve cord, an endostyle, pharyngeal slits, and a post-anal tail at some point in their development

Clitellum

specialized band of fused segments, which aids in reproduction

Cnidaria

phylum of animals that are diploblastic and have radial symmetry

Cnidocyte

specialized stinging cell found in Cnidaria

Conispiral

shell shaped coiled around a horizontal axis

Corona

wheel-like structure on the anterior portion of the rotifer that contains cilia and moves food and water toward the mouth

Ctenidium

specialized gill structure in mollusks

Cuticle (animal)

the tough, external layer possessed by members of the invertebrate class Ecdysozoa that is periodically molted and replaced

Cypris

larval stage in the early development of crustaceans

Echinodermata

phylum of deuterostomes with spiny skin; exclusively marine organisms

Enterocoelom

coelom formed by fusion of coelomic pouches budded from the endodermal lining of the archenteron

Epidermis

outer layer (from ectoderm) that lines the outside of the animal

Extracellular digestion

food is taken into the gastrovascular cavity, enzymes are secreted into the cavity, and the cells lining the cavity absorb nutrients

Gastrodermis

inner layer (from endoderm) that lines the digestive cavity

Gastrovascular cavity

opening that serves as both a mouth and an anus, which is termed an incomplete digestive system

Gemmule

structure produced by asexual reproduction in freshwater sponges where the morphology is inverted

Hemocoel

internal body cavity seen in arthropods

Hermaphrodite

referring to an animal where both male and female gonads are present in the same individual

Invertebrata

category of animals that do not possess a cranium or vertebral column

Madreporite

pore for regulating entry and exit of water into the water vascular system

Mantle

(also, pallium) specialized epidermis that encloses all visceral organs and secretes shells

Mastax

jawed pharynx unique to the rotifers

Medusa

free-floating cnidarian body plan with mouth on underside and tentacles hanging down from a bell

Mesoglea

non-living, gel-like matrix present between ectoderm and endoderm in cnidarians

Mesohyl

collagen-like gel containing suspended cells that perform various functions in the sponge

Metamerism

series of body structures that are similar internally and externally, such as segments

Mollusca

phylum of protostomes with soft bodies and no segmentation

Nacre

calcareous secretion produced by bivalves to line the inner side of shells as well as to coat intruding particulate matter

Nauplius

larval stage in the early development crustaceans

Nematocyst

harpoon-like organelle within cnidocyte with pointed projectile and poison to stun and entangle prey

Nematoda

phylum of worm-like animals that are triploblastic, pseudocoelomates that can be free-living or parasitic

Nemertea

phylum of dorsoventrally flattened protostomes known as ribbon worms

Osculum

large opening in the sponge’s body through which water leaves

Ostium

pore present on the sponge’s body through which water enters

Oviger

additional pair of appendages present on some arthropods between the chelicerae and pedipalps

Parapodium

fleshy, flat, appendage that protrudes in pairs from each segment of polychaetes

Pedipalp

second pair of appendages in Chelicerata

Pilidium

larval form found in some nemertine species

Pinacocyte

epithelial-like cell that forms the outermost layer of sponges and encloses a jelly-like substance called mesohyl

Planospiral

shell shape coiled around a vertical axis

Planuliform

larval form found in phylum Nmertea

Polymorphic

possessing multiple body plans within the lifecycle of a group of organisms

Polyp

stalk-like sessile life form of a cnidarians with mouth and tentacles facing upward, usually sessile but may be able to glide along surface

Porifera

phylum of animals with no true tissues, but a porous body with rudimentary endoskeleton

Radula

tongue-like organ with chitinous ornamentation

Rhynchocoel

cavity present above the mouth that houses the procoscis

Schizocoelom

coelom formed by groups of cells that split from the endodermal layer

Sclerocyte

cell that secretes silica spicules into the mesohyl

Seta / Chaeta

chitinous projection from the cuticle

Siphon

tubular structure that serves as an inlet for water into the mantle cavity

Spicule

structure made of silica or calcium carbonate that provides structural support for sponges

Spongocoel

central cavity within the body of some sponges

Trochophore

first of the two larval stages in mollusks

Uniramous

referring to one branch per appendage

Veliger

second of the two larval stages in mollusks

Water vascular system

system in echinoderms where water is the circulatory fluid

Zoea

larval stage in the early development of crustaceans

Acanthostega

one of the earliest known tetrapods