Question 1

What is the probable sequence in which the following animal clades originated, from earliest to most recent?

Accepted Answer

Bilaterians are the earliest animal clade, followed by deuterostomes, vertebrates, tetrapods, and amniotes.

Question 2

Which of the following statements concerning animal taxonomy is accurate?

Accepted Answer

The statement that animals evolved from flagellated protists similar to modern choanoflagellates is currently the most widely accepted theory of animal origins.

Question 3

The primary difference between a coelom and a pseudocoelom is ________.

Accepted Answer

The primary difference between a coelom and a pseudocoelom is their developmental origin. A coelom arises from the mesoderm while a pseudocoelom arises from the blastocoel.

Question 4

Some researchers claim that sponge genomes have homeotic genes, but no Hox genes. If true, this finding would ________.

Accepted Answer

The presence of homeotic genes but no Hox genes supports the idea that sponges are "basal animals" and likely diverged from the animal lineage before the evolution of Hox genes, which are important in determining body plan in more complex animals. It does not affect their classification as animals. The absence of Hox genes also does not necessarily mean that extinct sponges were the last common ancestor of animals and fungi, nor does it require sponges to be reclassified as choanoflagellates.

Question 5

Use the figure to answer the question.

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

Accepted Answer

Chordata and Echinodermata both have vastly different adult features, with Chordata including mammals, birds, reptiles, fish and amphibians, while Echinodermata includes animals like sea stars, sea urchins and sand dollars. However, recent genetic evidence suggests that they are each other's closest relatives, sharing a common ancestor that lived over 500 million years ago.

Question 6

At one time, sponges were lumped into one phylum. Then, they were separated into several different phyla. Now, they are considered one phylum again. These changes indicate which of the following?

Accepted Answer

The changes in the classification of sponges indicate that every phylogeny should be considered a hypothesis that must be revised in the light of new data. The classification of organisms is constantly being refined and updated based on new evidence and understanding, highlighting the need for a flexible and adaptable approach.

Question 7

If in the future the current molecular evidence regarding animal origins is further substantiated, which of the following statements would be correct with reference to fossil evidence that contradicts molecular evidence?

Accepted Answer

If the molecular evidence is further substantiated and contradicts the fossil evidence, it is more likely that the fossil evidence was incomplete or misinterpreted rather than being a hoax. Therefore, option B stating that the fossil evidence will be understood to have been incomplete or misinterpreted is the best answer. Options A and C are unlikely as science does not dismiss evidence as a hoax or ignore entire fields of research. Option D is extreme and unnecessary, as even small amounts of fossil evidence can still provide valuable information in constructing phylogenies.

Question 8

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

Accepted Answer

The most ancient branch point in animal phylogeny is the characteristic of having true tissues or no tissues. This is the difference between sponges (no tissues) and all other animals (true tissues). Radial or bilateral symmetry, diploblastic or triploblastic embryos, and a body cavity or no body cavity evolved later in animal evolution.

Question 9

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

Accepted Answer

Bilateral symmetry allows for animals to be streamlined for swimming, therefore is more advantageous for swimming animals. Radial symmetry is more common in sessile animals or slow-moving animals.

Question 10

Why might researchers choose to use molecular data (such as ribosomal RNA sequences) rather than morphological data to study the evolutionary history of animals?

Accepted Answer

Molecular data can be used to give an estimate of the time since two groups split.

Question 11

You find a new species of worm and want to classify it. Which of the following lines of evidence would allow you to classify the worm as a nematode and not an annelid?

Accepted Answer

The fact that the worm sheds its external skeleton to grow suggests that it is a nematode, as annelids do not have an external skeleton to shed. The other options (segmentation, triploblastic nature, and possession of a coelom) are shared by both nematodes and annelids.

Question 12

The common ancestor of the protostomes had a coelom. What does this suggest?

Accepted Answer

The presence of a coelom in the common ancestor suggests that the body cavity evolved before specific features like the lophophore.

Question 13

Use the figure to answer the question.
A: Morphological phylogeny.

B: Molecular phylogeny.

In the traditional phylogeny (A), the phylum Platyhelminthes is depicted as a sister taxon to the rest of the protostome phyla and as having diverged earlier from the lineage that led to the rest of the protostomes. In the molecular phylogeny (B), Platyhelminthes is depicted as a Lophotrochozoan phylum. What probably led to this change?

Accepted Answer

The shift in Platyhelminthes' placement from a sister taxon to the rest of the protostomes to being part of the Lophotrochozoa is likely due to the removal of the acoel flatworms from the Platyhelminthes group, which made the remaining flatworms a monophyletic clade that is clearly tied to the Lophotrochozoa in molecular phylogenies.

Question 14

When a scientist describes the "body plan" of a phylum, he or she is implying that ________.

Accepted Answer

The term "body plan" refers to the general structure, arrangement of organ systems, and integrated functioning of parts in an organism. It implies that certain body shapes have been more successful in evolutionary terms, leading to their persistence and prevalence.

Question 15

Use the figure to answer the question.

Which of the following statements is supported by the phylogeny in the figure?

Accepted Answer

The phylogeny shows examples of animals with extremely different adult forms (such as sea stars and sea urchins) being relatively closely related, which supports statement D. The diagram does not indicate that Deuterostoma are more evolutionarily advanced than Porifera (statement A), nor does it demonstrate that traits are always retained in later-evolving groups (statement B). Without additional information, it is impossible to determine if animals show evidence of convergent evolution in their traits (statement C).

Question 16

Nine-banded armadillos give birth to four offspring at a time. An amazing fact about these offspring is that they are genetically identical to each other. This fact suggests ________.

Accepted Answer

Genetically identical offspring suggest that the embryo underwent radial and indeterminate cleavage, where each blastomere has the ability to develop into a complete organism.

Question 17

In the future, phylogenetic studies should be conducted to ________.

Accepted Answer

Phylogenetic studies are used to uncover the evolutionary relationships between organisms. Conducting phylogenetic studies on the Lophotrochozoa would help resolve their branching patterns and help us better understand their evolutionary history.

Answer: C
 Conducting a phylogenetic study on nematodes and platyhelminthes would help us understand the evolutionary relationship between these two groups of organisms.

Answer: D
 While conducting a phylogenetic study on echinoderms might be interesting and informative, it is not as pressing a question as resolving the branching patterns of the Lophotrochozoa or discovering the relationship between nematodes and platyhelminthes. Therefore, option D is not the best choice.

Thus, the best choices are A and C.

Question 18

Use the figure to answer the question.

Which morphological trait evolved more than once in animals, according to the phylogeny based on DNA sequence data found in the figure?

Accepted Answer

The answer of Use the figure to answer the question.

Which...

Question 19

Use the table to answer the question.
Proposed Number of Hox Genes in Various Extant and Extinct Animals

What conclusion can best be drawn from the data in the table?

Accepted Answer

The data shows a significant increase in the number of Hox genes in vertebrates compared to invertebrates, which supports the hypothesis that the expansion in numbering throughout vertebrate evolution cannot be explained by only three duplications of the ancestral vertebrate Hox cluster. The data does not support choices A, B, or D.

Question 20

The last common ancestor of all bilaterians is thought to have had four Hox genes. Most extant cnidarians have two Hox genes, though some have three Hox genes. On the basis of these observations, some have proposed that the ancestral cnidarian's were originally bilateral and, in stages, lost Hox genes from their genomes. If true, this would mean that ________.

Accepted Answer

The observation that most extant cnidarians have only two Hox genes while the last common ancestor of all bilaterians had four Hox genes suggests that the ancestral cnidarians were originally bilateral and lost Hox genes over time, leading to the secondary development of radial symmetry in those lineages. Therefore, option B is the most appropriate choice. Options A, C, and D do not accurately reflect the information provided in the passage.

Quiz 32: An Overview of Animal Diversity

What is the probable sequence in which the following animal clades originated, from earliest to most recent?

Which of the following statements concerning animal taxonomy is accurate?

The primary difference between a coelom and a pseudocoelom is ________.

Some researchers claim that sponge genomes have homeotic genes, but no Hox genes. If true, this finding would ________.

Use the figure to answer the question. Which of the following pairs of animals show that animals with widely different adult features can be each other's closest relatives?

At one time, sponges were lumped into one phylum. Then, they were separated into several different phyla. Now, they are considered one phylum again. These changes indicate which of the following?

If in the future the current molecular evidence regarding animal origins is further substantiated, which of the following statements would be correct with reference to fossil evidence that contradicts molecular evidence?

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

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

Why might researchers choose to use molecular data (such as ribosomal RNA sequences) rather than morphological data to study the evolutionary history of animals?

You find a new species of worm and want to classify it. Which of the following lines of evidence would allow you to classify the worm as a nematode and not an annelid?

The common ancestor of the protostomes had a coelom. What does this suggest?

When a scientist describes the "body plan" of a phylum, he or she is implying that ________.

Use the figure to answer the question. Which of the following statements is supported by the phylogeny in the figure?

Nine-banded armadillos give birth to four offspring at a time. An amazing fact about these offspring is that they are genetically identical to each other. This fact suggests ________.

In the future, phylogenetic studies should be conducted to ________.

Use the figure to answer the question. Which morphological trait evolved more than once in animals, according to the phylogeny based on DNA sequence data found in the figure?

Use the table to answer the question. Proposed Number of Hox Genes in Various Extant and Extinct Animals What conclusion can best be drawn from the data in the table?