Chapter 2

Question 1

Metazoans

Answer 1

Oldest known fossil of multicellular animals

Question 2

Cambrian Explosion

Answer 2

Sudden appearance and rapid diversification of complex animals over several millions of years

Question 3

Metazoans

Answer 3

A multicellular organism

Question 4

Unicellular

Answer 4

Single celled

Question 5

Acellular

Answer 5

Without cells

Question 6

Bilaterally symmetrical

Answer 6

Right and left sides that are approximate mirror images of each other

Question 7

Cephalozation

Answer 7

The concentration of nervous and sensory tissues and organs at one end of an animal, resulting in distinct anterior and and posterior ends

Question 8

Radially symmetrical

Answer 8

Animal that can be divided into two approximately equal halves by any cut that passes through its center

Question 9

Asymmetrical invertebrates

Answer 9

Those having no ordered pattern to their gross invertebrates

Question 10

Germ layers

Answer 10

Groups of cells that behave as a unit during the early stages of embryonic development and give rise to distinctly different tissue and/or organ systems in adults

Question 11

Diploblastic animals

Answer 11

Only 2 distinct germ layers form during or following the movement of cells into the embryo’s interior

Question 12

Ectoderm

Answer 12

Outer most layer of cells

Question 13

Endoderm

Answer 13

Innermost layers of cells

Question 14

Triploblastic

Answer 14

Exhibiting three distinct tissue layers during embryonic development

Question 15

Mesoderm

Answer 15

An embryonic tissue layer that gives rise to certain tissues and organs of the adult, including the muscles and gonads (found in between the endoderm and ectoderm)

Question 16

Coelom

Answer 16

An internal body cavity lying between the gut and the outer body wall musculature that is lined with derivatives of the embryonic mesoderm

Question 17

Coleomate

Answer 17

Animals possessing a coelom

Question 18

Protostomes

Answer 18

having true tissues, being bilaterally symmetric, and developing the mouth before the anus during embryonic development

Coelom formation occurs by the gradual enlargement of a split in the mesoderm

Question 19

Schizocoely

Answer 19

The process of gradual enlargement of a split in the mesoderm

Question 20

Deuterostomes

Answer 20

This classification is based on the development of the embryo, where the blastopore (the first opening formed during embryonic development) becomes the anus in deuterostomes, while it becomes the mouth in protostomes.

Question 21

Enterocoely

Answer 21

Formation of a coelom through outpocketing of the inner portion of the archenteron in some animals (deuterostomes)

Question 22

Animal pole

Answer 22

The region with lower yolk density

Question 23

Vegetal pole

Answer 23

Opposite end of the lower yolk density

Question 24

Radial cleavage (pattern )

Answer 24

The spindles of a given cell (cleavage planes) are oriented either parallel or perpendicular to the animal/vegetal axis

Question 25

Spiral cleavage

Answer 25

Spindle axes are oriented at 45 degrees angles to the animal/vagetal axis. Doesn’t necessarily pass through the center of the dividing cell

Question 26

Micromeres

Answer 26

Smaller cells in spiral cleavage

Question 27

Macromeres

Answer 27

Larger cells in the process of spiral cleavaging

Question 28

Indeterminate (regulative) cleavage (mostly in deuterostomes)

Answer 28

Each cell retains the capacity to differentiate the entire organism if that cell loses contacts with its associates

Question 29

Determine/mosaic

Answer 29

Other words that are used to call protostome cleavage

Question 30

Polar lobe

Answer 30

A conspicuous bulge of cytoplasm that forms prior to cell division and that contains no nuclear material

Question 31

Blastocoel

Answer 31

An internal space that develops in the embryo before gastrulation

Question 32

Pseudocoel

Answer 32

Internal body cavity lying between the outer body wall musculature and the gut; not lined with mesoderm and generally formed by persistence of the embryonic blastocoel

Question 33

Pseudocoelomate

Answer 33

Organisms that develop a pseudocoel

Question 34

Acoelomate

Answer 34

Don’t have an internal body cavity

Question 35

Monophyletic

Answer 35

Members of a particular phylum that are presumed to have evolved from a single ancestral group

Question 36

Paraphyletic

Answer 36

Phylum of organisms that aren’t presumed to have evolved from a single ancestral form

Question 37

Species

Answer 37

The members of one species are reproductively isolated from members of all other species