Openstax Biology - Chapter 27 - Introduction To Animal Diversity

Front 1

acoelomate

Back 1

animal without a body cavity

Front 2

bilateral symmetry

Back 2

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

Front 3

blastopore

Back 3

indentation formed during gastrulation, evident in the gastrula stage

Front 4

blastula

Back 4

16–32 cell stage of development of an animal embryo

Front 5

body plan

Back 5

morphology or constant shape of an organism

Front 6

Cambrian explosion

Back 6

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

Front 7

cleavage

Back 7

cell division of a fertilized egg (zygote) to form a multicellular embryo

Front 8

coelom

Back 8

lined body cavity

Front 9

Cryogenian period

Back 9

geologic period (850–630 million years ago) characterized by a very cold global climate

Front 10

determinate cleavage

Back 10

developmental tissue fate of each embryonic cell is already determined

Front 11

deuterostome

Back 11

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

Front 12

diploblast

Back 12

animal that develops from two germ layers

Front 13

Ecdysozoa

Back 13

clade of protostomes that exhibit exoskeletal molting (ecdysis)

Front 14

Ediacaran period

Back 14

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

Front 15

enterocoely

Back 15

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

Front 16

eucoelomate

Back 16

animal with a body cavity completely lined with mesodermal tissue

Front 17

Eumetazoa

Back 17

group of animals with true differentiated tissues

Front 18

gastrula

Back 18

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

Front 19

germ layer

Back 19

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

Front 20

Hox gene

Back 20

master control gene that can turn on or off large numbers of other genes during embryogenesis; also known as homeobox gene

Front 21

indeterminate cleavage

Back 21

early stage of development when germ cells or “stem cells” are not yet pre-determined to develop into specific cell types

Front 22

Lophotrochozoa

Back 22

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

Front 23

mass extinction

Back 23

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

Front 24

Metazoa

Back 24

group containing all animals

Front 25

organogenesis

Back 25

formation of organs in animal embryogenesis

Front 26

Parazoa

Back 26

group of animals without true differentiated tissues

Front 27

protostome

Back 27

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

Front 28

pseudocoelomate

Back 28

animal with a body cavity located between the mesoderm and endoderm

Front 29

radial cleavage

Back 29

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

Front 30

radial symmetry

Back 30

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

Front 31

schizocoely

Back 31

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

Front 32

spiral cleavage

Back 32

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

Front 33

triploblast

Back 33

animal that develops from three germ layers