Chapter 27

Question 1

Tissues

Answer 1

An integrated group of cells with a common structure, function, or both

Question 2

Gastrovascular Cavity

Answer 2

A central cavity with a single opening in the body of certain animals, including cnidarians and flatworms, that functions in both the digestion and distribution of nutrients

Question 3

Cambrian Explosion

Answer 3

A relatively brief time in geologic history when many present-day phyla of animals first appeared in the fossil record. This burst of evolutionary change occurred about 535-525 million years ago and saw the emergence of the first large, hard-bodied animals.

Question 4

Bilaterians

Answer 4

Member of a clade of animals with bilateral symmetry and three germ layers

Question 5

Body Plan

Answer 5

In multicellular eukaryotes, a set of morphological and developmental traits that are integrated into a functional whole–the living organism

Question 6

Radial Symmetry

Answer 6

The body parts are arranged around a single main axis that passes through the center of the animal

Question 7

Bilateral Symmetry

Answer 7

The body parts are arranged around two axes of orientation, the head-tail axis and the dorsal vertical axis. Only one imaginary line divides the animal into mirror-image halves.

Question 8

Ectoderm

Answer 8

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

Question 9

Endoderm

Answer 9

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 in species that have these structures

Question 10

Mesoderm

Answer 10

The middle primary germ layer in a triploblastic animal embryo; develops into the notochord, the lining of the coelom, muscles, skeleton, gonads, kidneys, and most of the circulatory system in species that have these structures.

Question 11

Body Cavity

Answer 11

A fluid- or air-filled space located between the digestive tract and the outer body wall; also called a coelom.

Question 12

Invertebrates

Answer 12

An animal without a backbone. Invertebrates make up 95% of animal species.

Question 13

Vertebrates

Answer 13

A chordate animal with a backbone. Vertebrates include sharks and rays, ray-finned fishes, coelacanths, lungfishes, amphibians, reptiles, and mammals.

Question 14

Arthropods

Answer 14

A segmented, molting bilaterian animal with a hard exoskeleton and jointed appendages. Familiar examples include insects, spiders, millipedes, and crabs.

Question 15

Chordates

Answer 15

Member of the phylum Chordata, animals that at some point during their development have a notochord; a dorsal, hollow nerve cord; pharyngeal slits or clefts; and a muscular, post-anal tail

Question 16

Notochord

Answer 16

A longitudinal, flexible rod that runs along the anterior-posterior axis of a chordate in the dorsal part of the body

Question 17

Tetrapods

Answer 17

Member of a vertebrate clade characterized by limbs with digits. Tetrapods include mammals, amphibians, and birds and other reptiles.

Question 18

Amphibians

Answer 18

Member of the tetrapod class Amphibia, including salamanders, frogs, and caecilians

Question 19

Amniotes

Answer 19

Member of a clade of tetrapods named for a key derived character, the amniotic egg, which contains specialized membranes, including the fluid-filled amnion, that protect the embryo. Amniotes include mammals as well as birds and other reptiles.

Question 20

Amniotic Egg

Answer 20

An egg that contains specialized membranes that function in protection, nourishment, and gas exchange. The amniotic egg was a major evolutionary innovation, allowing embryos to develop on land in a fluid-filled sac, thus reducing the dependence of tetrapods on water for reproduction.

Question 21

Reptile

Answer 21

Member of the clade of amniotes that includes tuataras, lizards and snakes, turtles, crocodilians, and birds

Question 22

Ectothermic

Answer 22

Referring to organisms for which external sources provide most of the heat for temperature regulation

Question 23

Endothermic

Answer 23

Referring to organisms that are warmed by heat generated by their own metabolism. This heat usually maintains a relatively stable body temperature higher than that of the external environment.

Question 24

Mammals

Answer 24

Member of the class Mammalia, amniotes that have hair and mammary glands (glands that produce milk)

Question 25

Monotremes

Answer 25

An egg-laying mammal, such as a platypus or echidna. Like all mammals, monotremes have hair and produce milk, but they lack nipples.

Question 26

Marsupials

Answer 26

A mammal, such as a koala, kangaroo, or opossum, whose young complete their embryonic development inside a maternal pouch

Question 27

Eutherians

Answer 27

Placental mammal; mammal whose young complete their embryonic development within the uterus, joined to the mother by the placenta