Chapter 32 Vocab

Front 1

Define: acoelomate

Back 1

A solid-bodied animal lacking a cavity between the gut and outer body wall.

Front 2

Define: anterior

Back 2

Referring to the head end of a bilaterally symmetrical animal.

Front 3

Define: archenteron

Back 3

The endoderm-lined cavity, formed during the gastrulation process, that develops into the digestive tract of an animal.

Front 4

Define: bilateral symmetry

Back 4

Characterizing a body form with a central longitudinal plane that divides the body into two equal but opposite halves.

Front 5

Define: bilaterian

Back 5

Member of the clade Bilateria, animals with bilateral symmetry.

Front 6

Define: blastopore

Back 6

The opening of the archenteron in the gastrula that develops into the mouth in protostomes and the anus in deuterostomes.

Front 7

Define: blastula

Back 7

The hollow ball of cells marking the end stage of cleavage during early embryonic development.

Front 8

Define: body cavity

Back 8

A fluid-containing space between the digestive tract and the body wall.

Front 9

Define: body plan

Back 9

In animals, the set of morphological and developmental traits that define a grade (level of organizational complexity).

Front 10

Define: cleavage

Back 10

The process of cytokinesis in animal cells, characterized by pinching of the plasma membrane; specifically, the succession of rapid cell divisions without growth during early embryonic development that converts the zygote into a ball of cells.

Front 11

Define: coelom

Back 11

A body cavity completely lined with mesoderm.

Front 12

Define: coelomate

Back 12

Animal that possesses a true coelom (fluid-filled body cavity lined by tissue completely derived from mesoderm.

Front 13

Define: determinate cleavage

Back 13

A type of embryonic development in protostomes that rigidly casts the developmental fate of each embryonic cell very early.

Front 14

Define: deuterostome development

Back 14

In animals, a developmental mode distinguished by the development of the mouth from the blastpore; often also characterized by schizocoelous development of the body cavity and by spiral cleavage.

Front 15

Define: diploblastic

Back 15

Having two germ layers.

Front 16

Define: dorsal

Back 16

Pertaining to the back of a bilaterally symmetrical animal.

Front 17

Define: ecdysozoan

Back 17

Member of a group of animal phyla with protostome development that some systematists hypothesize form a clade, including many molting animals.

Front 18

Define: ectoderm

Back 18

The outermost of the three primary germ layers in animal embryos; gives rise to the outer covering and, in some phyla, the nervous system, inner ear, and lens of the eye.

Front 19

Define: Ediacaran fauna

Back 19

Earliest generally accepted animal fossils, dating from about 575 million years ago.

Front 20

Define: endoderm

Back 20

The innermost of the three primary germ layers in animal embryos; lines the archenteron and gives rise to the liver, pancreas, lungs, and the lining of the digestive tract.

Front 21

Define: enterocoelous

Back 21

Pattern of formation of the body cavity common in deuterostome development, in which the mesoderm buds from the wall of the archenteron and hollows, forming the body cavity.

Front 22

Define: eumetazoan

Back 22

Member of the clade Eumetazoa, animals with true tissues (all animals except sponges).

Front 23

Define: gastrula

Back 23

The three-layered, cup-shaped embryonic stage.

Front 24

Define: gastrulation

Back 24

The formation of a gastrula from a blastula.

Front 25

Define: germ layer

Back 25

Three main layers that form the various tissues and organs of an animal body.

Front 26

Define: grade

Back 26

Group of animal species that share the same level of organizational complexity.

Front 27

Define: indeterminate cleavage

Back 27

A type of embryonic development in deuterostomes, in which each cell produced by early cleavage divisions retains the capacity to develop into a complete embryo.

Front 28

Define: larva

Back 28

A free-living, sexually immature form in some animal life cycles that may differ from the adult in morphology, nutrition, and habitat.

Front 29

Define: lophophore

Back 29

A horseshoe-shaped or circular fold of the body wall bearing ciliated tentacles that surround the mouth.

Front 30

Define: lophotrochozoan

Back 30

Member of a group of animal phyla with protostome development that some systematists hypothesize form a clade, characterized by lophophores or trochophore larvae.

Front 31

Define: mesoderm

Back 31

The middle primary germ layer of an early embryo that develops into the notochord, the lining of the coelom, muscles, skeleton, gonads, kidneys, and most of the circulatory system.

Front 32

Define: metamorphosis

Back 32

The resurgence of development in an animal larva that transforms it into a sexually mature adult.

Front 33

Define: posterior

Back 33

Pertaining to the rear, or tail, of a bilaterally symmetrical animal.

Front 34

Define: protostome development

Back 34

In animals, a developmental mode distinguished by the development of the anus from the blastopore; often also characterized by enterocoelous development of the body cavity and by radial cleavage.

Front 35

Define: psuedocoelomate

Back 35

An animal whose body cavity is not completely lined by mesoderm.

Front 36

Define: radial cleavage

Back 36

A type of embryonic development in deuterostomes in which the planes of cell division that transform the zygote into a ball of cells are either parallel or perpendicular to the polar axis, thereby aligning tiers of cells one above the other.

Front 37

Define: radial symmetry

Back 37

Characterizing a body shaped like a pie or barrel, with many equal parts radiating outward like the spokes of a wheel; present in cnidarians and echinoderms.

Front 38

Define: schizocoelous

Back 38

Pattern of formation of the body cavity common in protostome development, in which initially solid masses of mesoderm split, forming the body cavity.

Front 39

Define: spiral cleavage

Back 39

A type of embryonic development in protostomes, in which the planes of cell division that transform the zygote into a ball of cells occur obliquely to the polar axis, resulting in cells of each tier sitting in the grooves between cells of adjacent tiers.

Front 40

Define: triploblastic

Back 40

Possessing three germ layers: the endoderm, mesoderm, and ectoderm. Most eumetazoans are triploblastic.

Front 41

Define: ventral

Back 41

Pertaining to the underside, or bottom, of a bilaterally symmetrical animal.

Front 42

Define: trochophore larva

Back 42

Distinctive larval stage observed in annelids and molluscs.