Question 1

A researcher has just discovered a new marine organism that appears very similar to jellyfish. However, on closer inspection, this organism possesses both a mouth and anal pore, and a single set of tentacles. This animal is MOST likely a:

Accepted Answer

The presence of both a mouth and anal pore, as well as a single set of tentacles, suggest that this organism is a comb-jelly. Comb-jellies are often mistaken for jellyfish, but possess distinct characteristics such as the presence of an anal pore. Placozoans, sea anemones, sponges, and choanoflagellates do not typically possess these characteristics.

Question 2

If you've ever read any stories about Sherlock Holmes, you may remember that he once solved a mystery in which a man died due to injuries sustained from a lion's mane jellyfish. Apparently, the victim encountered this free-floating jellyfish in a pool of water, was stung, and died suddenly. From this information, you can deduce that the victim encountered the jellyfish in what form?

Accepted Answer

The fact that the victim encountered the jellyfish in a pool of water suggests that it was a free-swimming form, which is the medusa stage of a jellyfish's life cycle. Polyps are typically attached to surfaces, anemones are stationary, trocophores are a type of larva, and placozoans are not known to have a swimming form.

Question 3

Which of the following is NOT a component of some sponge skeletons?

Accepted Answer

Cartilage is not a component of any sponge skeletons. Sponges can have skeletons made of protein, glasslike silica (SiO₂), and/or calcium carbonate (CaCO₃).

Question 4

Which of the following are cnidarians?

Accepted Answer

Cnidarians include jellyfish and sea anemones, but not sponges or mollusks.

Question 5

Consider the following phylogeny of protostomes.  One of the traits used to describe animals is the type of body cavity (coelom) that is present. According to the phylogeny, how many times did a coelom evolve in protostomes?

Accepted Answer

The answer of Consider the following phylogeny of protostomes. ...

Question 6

Which of the following statements is TRUE of the gastric cavity of cnidarians?

Accepted Answer

The gastric cavity of cnidarians contains digestive enzymes which allow them to consume their prey whole. After the prey is stored in the gastric cavity, digestion takes place in the stomach. Cnidarians do not have an anus, so excretion occurs through the same opening as the mouth.

Question 7

Cnidarians are able to capture prey with the aid of _____, harpoon-like organelles that are often tipped with neurotoxins.

Accepted Answer

Nematocysts are the harpoon-like organelles found in cnidarians that are used to capture prey. These organelles can be tipped with neurotoxins, which are used to immobilize or kill the prey. Choanocytes are found in sponges and are used for filter feeding. Mesoglea is a jelly-like substance found between the inner and outer layers of a cnidarian's body. Polyps are the sessile form of cnidarians, while medusae are the free-swimming form.

Question 8

Comb-jellies are similar to bilaterians in that they:

Accepted Answer

The answer of Comb-jellies are similar to bilaterians in that...

Question 9

If ctenophores are sister to all animal taxa, excluding cnidarians and placazoans, then:

Accepted Answer

The answer of If ctenophores are sister to all animal...

Question 10

Which of the following statements is TRUE of sponges?

Accepted Answer

None of the statements provided are true. Sponges do not have nerve cells, they do not produce nematocysts, and they do not have an anal pore. Additionally, the choanocytes of sponges and choanoflagellates share morphological similarities, as they both have a collar of microvilli surrounding a flagellum.

Question 11

Ctenopores (comb-jellies):

Accepted Answer

Ctenophores have a separate mouth and anal pore, allowing for a complete digestive system, unlike cnidarians which have a single opening serving as both mouth and anus.

Question 12

Which of the following is FALSE regarding cnidarians?

Accepted Answer

Cnidarians have a single opening that serves as both the mouth and the anus, not separate openings. This is a characteristic feature of their simple body plan.

Question 13

Placozoans:

Accepted Answer

Placozoans are simple, multicellular organisms with no true tissues or organs. They have a basic body plan consisting of a flattened, disc-like shape with cilia on the underside for movement and feeding. They reproduce both sexually and asexually. Genetic analysis shows that they are more closely related to animals such as sponges and ctenophores than to cnidarians.

Question 14

Compared to cnidarians, bilaterally symmetrical animals have _____ nervous systems.

Accepted Answer

Bilateral animals have centralized nervous systems, which means that their nerve cells are organized into a brain or series of ganglia that are located in a specific region of the body. This allows for more efficient processing of information and greater control over behavior. In contrast, cnidarians have simple nerve nets that are distributed throughout their body and do not exhibit centralized control.

Question 15

A researcher is culturing cells in a petri dish. After a few weeks, she notices that these cells have formed a "sheet," with junctions visible between individual cells. Which of the following statements is NOT true regarding these cultured cells?

Accepted Answer

Mesoglea is a jelly-like substance found between the epidermis and endodermis of jellyfish and other cnidarians. Cultured cells forming a sheet with visible junctions between individual cells may resemble an epithelium or the epidermis/endodermis of jellyfish, but they do not form mesoglea.

Question 16

Which of the following is NOT a cell or structure found in sponges?

Accepted Answer

Sponges do not have a true gastric cavity or digestive system. Instead, they rely on choanocytes and other cells to capture and digest food particles within the mesohyl. The pores in a sponge's body wall are important for filtering water and allowing exchange of nutrients and waste.

Question 17

Placozoans, which were first discovered in an aquarium, are by far the most diverse of the eumetazoans, with approximately 10,000 documented species.

Accepted Answer

Placozoans are actually one of the least diverse groups of eumetazoans, with only 6 recognized species.

Question 18

Placazoans are thought to branch early on the animal tree. Which of the following features of placozoans are consistent with this phylogenetic placement?

Accepted Answer

Placozoans' lack of a differentiated gut cavity and nerve cells, as well as their reliance on diffusion for gas exchange, are primitive features consistent with an early branching in the animal tree.

Question 19

Cnidarians have _____ symmetry.

Accepted Answer

Cnidarians have radial symmetry, which means they have multiple planes of symmetry that pass through a central axis. This allows them to detect and respond to stimuli from all directions. They do not have bilateral symmetry, which is found in animals with a distinct head and tail end, and a left and right side that are mirror images of each other. They also do not have circular symmetry, which is not a recognized form of symmetry in biology.

Question 20

Which of the following is NOT true of sponges?

Accepted Answer

Sponges are among the simplest animals and reproduce asexually most of the time. They do have specialized cell types, such as choanocytes and spicules, but they do not have true reproductive organs.

Quiz 44: Animal Diversity