Chapter 32: Animal Diversity

Question 1

Cleavage

Answer 1

The succession of rapid cell divisions without significant growth during early embryonic development that converts the zygote to a ball of cells.

Question 2

Radial symmetry

Answer 2

Symmetry in which the body is shaped like a pie (lacking a left side and a right side) and can be divided into mirror-imaged halves by any plane through its central axis.

Question 3

Blastopore

Answer 3

In a gastrula, the opening of the archenteron that typically develops into the anus in deuterostomes and the mouth in protostomes.

Question 4

Coelom

Answer 4

A body cavity lined by tissue derived only from mesoderm.

Question 5

Ectoderm

Answer 5

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 6

Gastrulation

Answer 6

In animal development, a series of cell and tissue movements in which the blastula-stage embryo folds inward, producing a three-layered embryo the gastrula.

Question 7

Larva

Answer 7

A free-living, sexually immature form in some animal life cycles that may differ from the adult animal in morphology, nutrition, and habitat.

Question 8

Blastula

Answer 8

A hollow ball of cells that marks the end of the cleavage stage during early embryonic development in animals.

Question 9

Metamorphosis

Answer 9

A developmental transformation that turns an animal larva into either an adult or an adult-like stage that is not yet sexually mature.

Question 10

Deuterostome development

Answer 10

In animals, a developmental mode distinguished by the development of the anus from the blastopore; often also characterized by the radial cleavage and by the body cavity forming as outpockets of mesodermal tissue.

Question 11

Archenteron

Answer 11

The endoderm-lined cavity, formed during gastrulation, that develops into the digestive tract of an animal.

Question 12

Ediacaran biota

Answer 12

An early group of macroscopic, soft-bodied, multicellular eukaryotes known from fossils that range in age from 635 million to 535 million years old.

Question 13

Endoderm

Answer 13

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 14

Eight-cell stage

Answer 14

The stage in embryo development after three rounds of cell division.

Question 15

Protostome development

Answer 15

In animals, a developmental mode distinguished by the development of the mouth from the blastopore; often also characterized by spiral cleavage and by the body cavity forming when solid masses of mesoderm split.

Question 16

Mesozoic era

Answer 16

The geological era known as the “age of reptiles;” includes the Cretaceous, Jurassic, and Triassic periods. Characterized by the origin of mammals and angiosperms and by the extinction of dinosaurs. Approximately 252-66 MYA.

Question 17

Mesoderm

Answer 17

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 18

Body plan

Answer 18

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

Question 19

Cenozoic era

Answer 19

The geological era that includes the Quaternary, Neogene, and Paleogene periods. Characterized by radiation of mammals, birds, and pollinating insects, by angiosperm dominance, by the origin of primate groups, and by the ice ages. Approximately 66-0.01 MYA.

Question 20

Gastrula

Answer 20

An embryonic stage in animal development encompassing the formation of three layers: ectoderm, mesoderm, and endoderm.

Question 21

Pseudocoelom

Answer 21

An animal whose body cavity is lined by tissue derived from mesoderm and endoderm.

Question 22

Hox genes

Answer 22

A homeobox-containing family of genes that plays an important role in the development of animal embryos and the expression of morphology.

Question 23

Lophophore

Answer 23

In some lophotrochozoan animals, including brachiopods, a crown of ciliated tentacles that surround the mouth and function in feeding.

Question 24

Tissue

Answer 24

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

Question 25

Acoelomate

Answer 25

A solid-bodied animal lacking a cavity between the gut and outer body wall.

Question 26

Lophotrochozoa

Answer 26

One of the three main lineages of bilaterian animals; it includes organism that have lophophores or trochophore larvae.

Question 27

Paleozoic era

Answer 27

The geological era that includes the Permian, Carboniferous, Devonian, Silurian, Ordovician, and Cambrian periods. Characterized by the Cambrian explosion, the colonization of land, the origin of reptiles, tetrapods, forests of vascular plants, and insects, and a mass extinction at its end. Approximately 541-252 MYA.