Chapter 32 - An Overview of Animal Diversity

Question 1

Animals -

Answer 1

Multicellular eukaryotes

Question 2

Tissues -

Answer 2

groups of similar cells that act as a functional unit

Question 3

Cleavage -

Answer 3

a succession of mitotic cell divisions without cell growth between the divisions

Question 4

A blastula -

Answer 4

a multicellular embryonic stage

Question 5

Process of gastrulation -

Answer 5

during which the layers of embryonic tissues that will develop into adult body parts are produced

Question 6

A gastrula -

Answer 6

resulting developmental stage of gastrulation

Question 7

A larva -

Answer 7

a sexually immature form of an animal that is morphologically distinct from the adult, usually eats different food, and may even have a different habitat than the adult

Question 8

Metamorphosis -

Answer 8

a developmental transformation that turns the animal into a juvenile that resembles an adult but is not yet sexually mature

Question 9

Hox genes -

Answer 9

play important roles in the development of animal embryos, controlling the expression of many other genes that influence morphology

Question 10

Ediacaran biota

Answer 10

members of an early group of mostly soft-bodied multicellular eukaryotes, the first generally accepted macroscopic fossils of animals from about 560 million years ago

Question 11

Cambrian explosion

Answer 11

wave of animal diversification occuring 535–525 million years ago, early in the Cambrian period of the Paleozoic era

Question 12

bilaterians

Answer 12

a clade whose members typically have a two-sided or a bilaterally symmetric form and a complete digestive tract, an efficient digestive system that has a mouth at one end and an anus at the other.

Question 13

A body plan -

Answer 13

is a particular set of morphological and developmental traits that are integrated into a functional whole—the living animal

Question 14

Sessile -

Answer 14

living attached to a substrate

Question 15

planktonic

Answer 15

drifting or weakly swimming, such as jellies, commonly called jellyfishes

Question 16

Ectoderm

Answer 16

the germ layer covering the surface of the embryo

Question 17

Endoderm

Answer 17

the innermost germ layer, lines the pouch that forms during gastrulation (the archenteron) and gives rise to the lining of the digestive tract (or cavity) and to the lining of organs such as the liver and lungs of vertebrates

Question 18

Diploblastic -

Answer 18

animal groups that have only these two germ layers

Question 19

Mesoderm -

Answer 19

All bilaterally symmetrical animals have a third germ layer which fills much of the space between the ectoderm and endoderm

Question 20

Triploblastic -

Answer 20

animals with bilateral symmetry and three germ layers

Question 21

a body cavity -

Answer 21

a fluid- or air-filled space located between the digestive tract (endoderm) and the outer body wall (ectoderm)

Question 22

a coelom -

Answer 22

a body cavity that forms from tissue derived from mesoderm. The inner and outer layers of mesoderm that surround the cavity connect and form structures that suspend the internal organs

Question 23

a hemocoel -

Answer 23

a body cavity that forms between the mesoderm and endoderm. A hemocoel contains hemolymph, a fluid that functions in the internal transport of nutrients and waste

Question 24

Spiral cleavage -

Answer 24

in which the planes of cell division are diagonal to the vertical axis of the embryo; as seen in the eight-cell stage of the embryo, smaller cells are centered over the grooves between larger, underlying cells

Question 25

Determinate cleavage -

Answer 25

of some animals with protostome development rigidly casts (“determines”) the developmental fate of each embryonic cell very early

Question 26

Radial cleavage -

Answer 26

the cleavage planes are either parallel or perpendicular to the vertical axis of the embryo; as seen at the eight-cell stage, the tiers of cells are aligned, one directly above the other

Question 27

Indeterminate cleavage -

Answer 27

meaning that each cell produced by early cleavage divisions retains the capacity to develop into a complete embryo

Question 28

the archenteron

Answer 28

formed during gastrulation, an embryo’s developing digestive tube initially forms as a blind pouch which becomes the gut

Question 29

Blastopore -

Answer 29

the indentation that during gastrulation leads to the formation of the archenteron