Ch 34: Circulation and Gas Exchange

Question 1

Not all organisms have circulatory systems, including:

cnidarians
ctenophores
flatworms

In these organisms, their body is only 1-2 cells thick, and gases can be exchanged directly with their _________. Nutrients can also be transported throughout the ____________ cavity.

Answer 1

environment
gastrovascular

Question 2

A circulatory system is only needed when the animal’s body is large enough that _________ is not sufficient to transport materials around the body.

Answer 2

diffusion

Question 3

Surface area to volume ratio of an animal’s body. As an organism gets bigger, its surface area-to-volume ratio _________. So if diffusion happens in relation to the surface area, the larger an animal, the less effective diffusion is at transporting materials. In other words, if the SA:V ratio is high, diffusion is sufficient. If the SA:V is low, diffusion is NOT sufficient.

Answer 3

decreases

Question 4

Circulatory systems are either open or closed. In an open circulatory system, the circulatory fluid, called _________, is also the interstitial fluid that bathes body cells. Arthropods, such as grasshoppers, and some molluscs, such as clams, have an open circulatory system.

Answer 4

hemolymph

Question 5

In a closed circulatory system, a circulatory fluid called blood is confined to vessels and is distinct from the interstitial fluid. This type of circulatory system is found in annelids (including earthworms), many molluscs, and all __________.

Answer 5

vertebrates

Question 6

In closed circulatory systems, one or more hearts pump blood into large vessels that branch into smaller ones that infiltrate the tissues and organs. ________ exchange occurs between the blood and the interstitial fluid, as well as between the interstitial fluid and body cells.

Answer 6

Chemical

Question 7

The open circulatory system is less ____________ expensive than the closed circulatory system.

Answer 7

energetically

Question 8

Which of the following describes the path taken by oxygen-rich blood?

From the heart to the gills
From the lungs to the body tissues
From the body tissues to the heart
From the gills to the heart
From the gills to the body tissues

Answer 8

From the gills to the body tissues

Red indicates vessels that carry oxygen-rich blood. In fish, blood picks up oxygen as it passes through the gills. This oxygen-rich blood then travels directly to the body tissues, where the oxygen is used.

Question 9

In the capillary beds of the gills, an oxygen gradient exists along the ______ length of the capillary.

Answer 9

entire

Question 10

What happens when the CO₂ level from cellular respiration increases in the blood?

Answer 10

A decrease in the pH of the cerebrospinal fluid triggers the brain’s breathing control centers, which stimulate diaphragm and rib muscle contractions.