Mastering Biology :Ch 32, 33.1, 33.2

Depending on the blastopore fate of its members, label each branch with P (for protostomy), D (for deuterostomy), N (for neither), or P & D. Labels may be used once, more than once or not at all.

Acoela- N Echinodermata- D Chordata- D Platyhelminthes- P Rotifera- P Mollusca- P & D Annelida- P & D Nematode- P Arthropoda- P & D

Chapter 33 Question 1 Part A - Identifying body symmetry Which type of symmetry does each of the following animals display? Drag each picture to the appropriate bin.

Asymmetry: Sponge Radial Symmetry: Jelly, Hydra Bilateral Symmetry: Bobcat, Turtle, Snake, Octopus Animal bodies may exhibit symmetry or a lack of symmetry (asymmetry). Some symmetrical animals exhibit radial symmetry, in which the body is wheel- or spoke-shaped, with no obvious front, back, right, or left. Other symmetrical animals exhibit bilateral symmetry, in which the body has left and right sides, a front and back, and a top and bottom.

Which of the following statements comparing symmetry in sessile and swimming animals is most probable?

Bilaterally symmetric animals can be streamlined for swimming, but radially symmetric animals cannot.

Which of the following pairs of animals show that animals with widely different adult features can be each other's closest relatives?

Chordata and Echinodermata

During embryological development, the anus forms before the mouth in _____. See Concept 32.3 (Page 679)

Humans -During gastrulation, the developing digestive tube of the embryo initially has a single opening, the blastopore. After the archenteron develops, a second opening forms at the opposite end of the gastrula. The mouth of many protostomes develops from the first opening, whereas in deuterostomes the mouth is derived from the second opening.

A graduate student finds an organism in a pond and thinks it is a freshwater sponge. A postdoctoral student thinks it looks more like an aquatic fungus. How can they decide whether it is an animal or a fungus?

Look for cell walls under a microscope. Fungal cells have cell walls, and animal cells do not.

Gastrulation is the process that directly forms the _____

Primary germ layers Gastrulation gives rise to either two or three germ layers.

Placing sponges as the basal metazoans on the basis of lack of tissues implies which of the following?

Sponge ancestors never had tissues

Which of the following is a feature of the "tube-within-a-tube" body plan in most animal phyla?

The mouth and anus form the ends of the inner tube

Which of the following is radially symmetrical?

a doughnut A doughnut has no front, no back, no left, and no right.

Which of the following would you classify as something other than an animal?

choanoflagellates

The fact that choanoflagellates and collar cells of sponges resemble each other supports the inference that ________.

choanoflagellates and sponges are sister groups

What was an early selective advantage of a coelom in animals? A coelom _____.

contributed to a hydrostatic skeleton, allowing greaterrange of motion

The last common ancestor of all animals was probably a _____.

flagellated protist

An organism that exhibits a head with sensory equipment and a brain probably also ________.

is bilaterally symmetrical

Which of the following is (are) unique to animals?

nervous conduction and muscular movement

Which tissue type or organ is not correctly matched with its germ layer tissue?

nervous-mesoderm

What do animals ranging from corals to monkeys have in common?

presence of Hox genes

The distinction between sponges and other animal phyla is based mainly on the absence versus the presence of

true tissues

The most ancient branch point in animal phylogeny is the characteristic of having _____.

true tissues or no tissues

Which of the following is NOT a characteristic of all animals? See Concept 32.3 (Page 677)

They have tissues, organs, and organ systems. Sponges are considered animals, and they lack these levels of organization.

Chapter 33 Question 2 Part B - Germ layers, tissues, and body cavities Animal tissues develop from embryonic germ layers. Triploblastic animals have three germ layers (ectoderm, mesoderm, and endoderm) and three basic body plans related to body cavities (acoelomate, pseudocoelomate, and coelomate). Select the three statements that are true.

A diploblast has no mesoderm. A pseudocoelom has the same functions as a true coelom. In a coelomate, the tissue lining the inner side of the body cavity arises from the same germ layer as the tissue lining the outer side of the body cavity.

Which feature of deuterostome development explains the formation of identical human twins?

Deuterostomes have indeterminate development. Most deuterostomes have indeterminate cleavage, meaning that each cell produced by early cleavage divisions retains the capacity to develop into a complete embryo. For example, if the cells of a sea urchin embryo are isolated at the four-cell stage, each can form a complete larva. It is the indeterminate cleavage of the human zygote that makes identical twins possible

Which of the following animals does NOT have a body cavity? See Concept 32.3 (Page 678)

Flatworm -Flatworms are acoelomates, even those that are not classified as acoels.

An important trend in animal evolution was cephalization. An animal is said to show cephalization when it _____. See Concept 32.3 (Page 677)

Has an aggregation of sensory neurons at the anterior end -Cephalization is an evolutionary trend toward the concentration of sensory equipment at the anterior end. It is associated with bilateral symmetry.

for the common ancestor of all the Bilateria, what was the fate of the blastopore?

It is impossible to tell from the data provided. Based on the phylogeny, the ancestral condition in bilaterians may have been similar to that in Acoela, where the blastopore closes and the mouth forms elsewhere (N); however, it is also possible that blastopore fate in Acoela is a derived trait and hence is not informative about the ancestral condition.

Which of the following statements concerning animal taxonomy is accurate?

Kingdom Animalia is monophyletic. Animals are thought to have evolved from flagellated protists similar to modern choanoflagellates.

How many times has blastopore fate changed over the course of evolution?

Multiple times, though the exact number is uncertain. The phylogeny indicates that blastopore fate has changed multiple times over the course of evolution. However, a precise determination cannot be made. For example, if we assume that the ancestral condition was similar to that in Acoela and that the common ancestor of all non-Acoela bilaterians (marked with a 1 on the tree) exhibited protostomy, then blastopore fate has changed at least five times: once in common ancestor 1, once in Deuterostomia, at least once in Mollusca, at least once in Annelida, and at least once in Arthropoda. Other assumptions would lead to different estimates.

Chapter 33 Question 3 Part C - Differences in development between protostomes and deuterostomes Many animals can be categorized as either protostomes and deuterostomes based on certain features of their embryonic development. Determine whether each of the following terms applies to only protostomes, only deuterostomes, both protostomes and deuterostomes, or neither. Drag each item to the appropriate bin. To review protostome and deuterostome characteristics, see the Hints.

Protosome: Mouth from blastosphere; Spiral, determinate cleavage; coelum from solid masses of mesoderm Deuterostome: Anus from blastosphere; radial, indeterminate cleavage; coelum from folds of archenteron Both: Tripoblast Neither: Diploblast

Both animals and fungi are heterotrophic. What distinguishes animal heterotrophy from fungal heterotrophy is that most animals derive their nutrition by _____.

ingesting it