Question 1

Which of the following best describes the body cavity organization of an acoelomate animal, such as a planarian?

Accepted Answer

No body cavity between the digestive tract and body wall; the space is filled with tissue derived from mesoderm.

Question 2

The flame-cell system in planarians is primarily responsible for which physiological process?

Accepted Answer

Excretion of metabolic wastes and osmoregulation.

Question 3

Which structure in the earthworm is responsible for separating internal segments and allowing for independent movement of each segment?

Accepted Answer

Septum

Question 4

In the life cycle of Schistosoma (blood fluke), which host is required for the larval stage before infecting humans?

Accepted Answer

Snail

Question 5

Which of the following is a key difference between the digestive systems of planarians and earthworms?

Accepted Answer

Earthworms have a complete digestive tract with specialized regions, while planarians have a gastrovascular cavity with a single opening.

Question 6

Which of the following equations best represents the relationship between surface area ($$A) $$and volume ($$V) $$for a flatworm, and why is this relationship important?

Accepted Answer

$$A \propto V$$^{2/3}$$; important because a high surface area to volume ratio allows for efficient diffusion of gases and nutrients.

Question 7

Which of the following best describes the function of the clitellum in earthworms?

Accepted Answer

It is involved in reproduction by secreting a cocoon for eggs.

Question 8

A pseudocoelomate animal, such as a nematode, differs from a coelomate in which way?

Accepted Answer

The pseudocoelom is a body cavity not completely lined with mesoderm.

Question 9

Which of the following is a correct sequence of structures that food passes through in the earthworm digestive system?

Accepted Answer

Mouth → Pharynx → Crop → Gizzard → Intestine → Anus

Question 10

Which of the following statements about the nervous system of planarians is correct?

Accepted Answer

They have a ladder-like nervous system with two ventral nerve cords and cerebral ganglia.

Question 11

Which adaptation allows earthworms to efficiently exchange gases with their environment?

Accepted Answer

Thin, moist skin that allows for diffusion of gases.

Question 12

In the tapeworm Taenia, what is the primary function of the proglottids?

Accepted Answer

Reproduction; each proglottid contains both male and female reproductive organs.

Question 13

Which of the following best explains why nematodes are more flexible than annelids?

Accepted Answer

Nematodes have only longitudinal muscles, allowing for whip-like movements, while annelids have both circular and longitudinal muscles for peristalsis.

Question 14

Which of the following is a key feature of the closed circulatory system in earthworms?

Accepted Answer

Blood is pumped by a dorsal vessel and a series of aortic arches.

Question 15

Which of the following best describes the excretory system of annelids?

Accepted Answer

Metanephridia filter coelomic fluid and excrete waste through nephridiopores.

Question 16

Which of the following is a correct statement about the reproductive strategy of tapeworms?

Accepted Answer

They are hermaphroditic, with each proglottid containing both male and female organs.

Question 17

Which of the following is a major evolutionary advantage of a true coelom (as seen in annelids) compared to a pseudocoelom?

Accepted Answer

It provides a space for the development and suspension of complex organs, and allows for more efficient movement.

Question 18

Which of the following best explains why flatworms (Platyhelminthes) are limited in thickness?

Accepted Answer

They lack a circulatory system and rely on diffusion for gas exchange.

Question 19

Which of the following is a correct pairing of animal group and body cavity type?

Accepted Answer

Earthworm – coelomate

Body Plans and Organ Systems of Worms: Flatworms, Roundworms, and Segmented Worms

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