Chapter 9

Question 1

Asymmetry

Answer 1

the lack or absence of symmetry

Question 2

Radial Symmetry

Answer 2

symmetry around a central axis, as in a starfish or tulip flower

Question 3

Bilateral Symmetry

Answer 3

symmetrical arrangement of an organism or part of an organism along a central axis so an organism can be divided into two equal halves

Question 4

Ectoderm

Answer 4

one of three primary germ layers. The ectoderm is the most exterior layer of skin

Question 5

Endoderm

Answer 5

Innermost of the primary germ layers. Gives rise to the respiratory tract, gastrointestinal tract.

Question 6

Mesoderm

Answer 6

One of three primary germ layers. Middle layer giving rise to a number of structures including bone, muscle, connective tissue and middle layer of skin

Question 7

Diploblastic

Answer 7

describing an animal with a body wall composed only of two layers, ectoderm and endoderm

Question 8

Triploblastic

Answer 8

describing an animal having a body composed of three germ cell layers

Question 9

Protostome

Answer 9

first opening in the embryo becomes the mouth. At this stage of development the later specialization of any given embryonic cell has already been determined.

Question 10

Radial Cleavage

Answer 10

cleavage that is typical of deuterostomes and that is characterized by arrangement of the blastomeres of each upper tier directly over those of the next lower tier resulting in radial symmetry

Question 11

Spiral Cleavage

Answer 11

cleavage that is typical of protostomes and that is characterized by arrangement of the blastomeres of each upper tier over the cell junctions of the next lower tier

Question 12

Deuterostome

Answer 12

distinguished from protostomes by their deuterostomic embryonic development. The first opening becomes the anus rather than the mouth

Question 13

Coelom

Answer 13

fluid filled body cavity that is completely lined by tissue created from the mesoderm.

Question 14

Pseudocoelom

Answer 14

second body cavity which occupies a space between the mesoderm of the body wall and the endoderm of the gut

Question 15

Acoelomate

Answer 15

an invertebrate lacking a coelom. such as flatworms and characterized by bilateral symmetry and a digestive cavity that is the only internal cavity

Question 16

Lophotrochozoa

Answer 16

One of the two distinct clades within protostomes

Question 17

Ecdysozoa

Answer 17

Other major grouping of clades including Arthropoda, Nematoda etc

Question 18

Incomplete Gut

Answer 18

only have one opening for food intake and waste removal

Question 19

Complete Gut

Answer 19

clear beginning and end with separate openings for food and waste

Question 20

Metamerism

Answer 20

phenomenon of having a linear series of body segments fundamentally similar in structure. Each segment is called somites or metameres