Question 1

You are examining a new animal species.You find that you can pass a line through any longitudinal plane and find equal halves.Evaluate the symmetry of this animal.

Accepted Answer

Radial symmetry is characterized by the ability to divide an organism into roughly equal halves through any longitudinal plane, which matches the description provided.

Question 2

What does the mesoderm have to do with the designation of a true coelom?

Accepted Answer

The mesoderm gives rise to the lining of the coelom, which is a fluid-filled body cavity completely surrounded by mesoderm-derived tissue. This is why the presence of a true coelom (as opposed to a pseudocoelom or no coelom) is closely linked to the development of mesoderm during embryonic development.

Question 3

If it were found that all animals except the Parazoa had a particular set of genes,one could conclude

Accepted Answer

The absence of these particular genes in Parazoa would suggest that they are likely related to the embryonic formation of tissues. This would lead to a better understanding of animal evolution and development. The other options are not necessarily true based on the given information.

Question 4

What is the primary characteristic that groups phyla within the Ecdysozoa?

Accepted Answer

The primary characteristic that groups phyla within the Ecdysozoa is the shedding of their exoskeletons. Ecdysozoa includes phyla such as Arthropoda (insects, crustaceans), Nematoda (roundworms), and Tardigrada (water bears), all of which molt their exoskeletons to grow and develop. The other choices, such as having tropchophore larvae, spiral cleavage, or segmentation, are characteristics found in other groups of animals but not specific to Ecdysozoa.

Question 5

If you conducted an experiment in which you took a complete animal that had no germ layers and strained it through a fine-mesh cloth so that all its cells separated,then you placed all the cells together and they reunited to form a new animal,to which phylum would that animal likely belong? (This was an actual experiment. )

Accepted Answer

Porifera, also known as sponges, are the only animals that lack true germ layers. In addition, sponges have pluripotent cells, meaning that they have the ability to differentiate into any cell type, allowing for the regeneration of lost parts and even the entire organism from small fragments. Therefore, if a complete sponge were to be separated into individual cells and those cells were allowed to reintegrate, a new sponge would likely form.

Question 6

If a coelom had been present in a species but was then lost over time,which function would you hypothesize could be most affected?

Accepted Answer

The coelom, a fluid-filled cavity found in many animals, plays a crucial role in the structure and function of the musculoskeletal system. Its loss would most directly impact the muscular system, as the coelom acts as a hydrostatic skeleton that supports and facilitates muscle contraction and movement.

Question 7

The animal kingdom is a monophyletic grouping.

Accepted Answer

The animal kingdom is monophyletic, meaning that all organisms in this group share a common ancestor and have evolved from a single lineage. This is supported by molecular and morphological evidence.

Question 8

Compare a pseudocoelom to a coelom.

Accepted Answer

A coelom is completely surrounded by mesoderm whereas a pseudocoelom has an outer covering of mesoderm and an inner one of endoderm.

Question 9

The placement of the phylum Platyhelminthes in the phylogenetic tree differs between a morphologically based phylogeny and a molecular based phylogeny.How do scientists best differentiate the interpretation based on molecular phylogeny?

Accepted Answer

The answer of The placement of the phylum Platyhelminthes in...

Question 10

Echinoderms are classified as Bilateria,but although they start out as bilateral larvae,they change into radially symmetrical adults.You might hypothesize that their genes controlling the development of radial symmetry are

Accepted Answer

Echinoderms, despite their adult radial symmetry, are more closely related to bilaterally symmetrical animals than to other radially symmetrical animals. Their genes for radial symmetry likely evolved independently.

Question 11

Suppose you discover a new species of animal that does not have body segments,but is triploblastic,coelomate,and cephalized.Under the molecular phylogenetic scheme,you would allocate it to which phylum?

Accepted Answer

Mollusca is the correct phylum because animals in this group are triploblastic, coelomate, and cephalized, and they do not necessarily have body segments, distinguishing them from segmented phyla like Arthropoda.

Question 12

Ecdysis is

Accepted Answer

Ecdysis refers to the molting of the exoskeleton, which is a characteristic feature of many invertebrates, such as insects, crustaceans, and arachnids. During ecdysis, the old exoskeleton is shed, and a new one is formed, allowing for growth and development.

Question 13

What is a valid distinction between a blastocoel,an archenteron,and a coelom?

Accepted Answer

The blastocoel is the first cavity that forms during early embryonic development, followed by the formation of the archenteron, which eventually develops into the digestive tract, and finally, the coelom, which forms body cavities such as the thoracic and abdominal cavities. This sequence reflects the typical progression of cavity formation during embryogenesis.

Question 14

A pseudocoelom is a cavity that develops into the coelom during embryonic development.

Accepted Answer

A pseudocoelom is a body cavity that is not entirely lined with mesoderm, and does not develop into a true coelom during embryonic development. True coeloms are lined with mesoderm, which differentiates into the tissues that give rise to muscles and other organs.

Question 15

A hydrostatic skeleton has no bones or cartilage.

Accepted Answer

A hydrostatic skeleton consists of a fluid-filled cavity surrounded by muscle tissue, which generates the necessary pressure to support and move the body. Therefore, there are no bones or cartilage in this type of skeleton.

Question 16

If two otherwise dissimilar organisms share similar genomic DNA,to what would you attribute the genomic similarity?

Accepted Answer

Similar genomic DNA suggests a close evolutionary relationship between the two organisms. It is possible that they are more closely related than previously thought, and share a common ancestor in their evolutionary history.

Question 17

An acoelomate is an animal that

Accepted Answer

An acoelomate is an animal that lacks both a true coelom and a pseudocoelom. These animals have a solid body without a fluid-filled cavity. Examples of acoelomates include flatworms and tapeworms.

Question 18

What phyla of animals has the greatest number of species?

Accepted Answer

Arthropoda is the phylum with the greatest number of species, including insects, spiders, crustaceans, and other groups.

Question 19

Gastrulation is the development of the gastrula into an embryo.

Accepted Answer

Gastrulation is the process during early embryonic development that transforms the blastula into a multilayered structure known as the gastrula, not the development of the gastrula into an embryo.

Question 20

The polymerase chain reaction (PCR)is used as a tool for

Accepted Answer

PCR is primarily used to amplify a specific segment of DNA, producing a large quantity of that particular DNA sequence.

The other options are not accurate. A is incorrect because PCR does not break down DNA, rather it copies it. C is incorrect because PCR does not fragment DNA, it amplifies a specific segment. D is incorrect because PCR does not rearrange gene sequences, it copies them. E is incorrect because PCR does not extract DNA, it amplifies it.

Quiz 25: Animal Diversity: Invertebrates