Skip to ContentGo to accessibility page
OpenStax Logo
Biology for AP® Courses

Critical Thinking Questions

Biology for AP® CoursesCritical Thinking Questions

Critical Thinking Questions

23 .
Define a closed circulatory system and compare the differences in heart structure for animals with closed circulatory systems.
  1. A closed circulatory system is a system in which the blood mixes with the interstitial fluid. Fish have a two-chambered heart. Amphibians and reptiles have a three-chambered heart, but the latter has little mixing of blood. Mammals and birds have a four-chambered heart and double circulation.
  2. A closed circulatory system is a system in which blood is separate from the interstitial fluid. Fish have a two-chambered heart. Amphibians and reptiles have a three-chambered heart, but the latter has little mixing of blood. Mammals and birds have a four-chambered heart and double circulation.
  3. A closed circulatory system is a system in which blood is separate from the interstitial fluid. Amphibians have a two-chambered heart. Fishes and reptiles have a three-chambered heart, but the latter has little mixing of blood. Mammals and birds have a four-chambered heart and double circulation.
  4. A closed circulatory system is a system in which blood mixes with the interstitial fluid. Amphibians have a two-chambered heart. Fishes and reptiles have a three-chambered heart, but the latter has little mixing of blood. Mammals and birds have a four-chambered heart and double circulation.
24 .
A circulatory system is the main method for transporting gases and nutrients throughout the body. Explain what happens in a closed circulatory system and compare a closed circulatory system to an open closed circulatory system.
  1. Blood in closed circulatory system is present inside blood vessels and circulates unidirectional from the heart, around the systemic circulatory route, then returns to the heart. It is less controlled and structured than an open circulatory system, but nutrients and waste products are transported more efficiently.
  2. Blood in closed circulatory system is not enclosed in blood vessels, but is pumped into a hemocoel, which circulates around the organs, then reenters the heart through ostia. It is more structured, controlled, and nutrients and waste products are transported more efficiently.
  3. Blood in closed circulatory system is not enclosed in blood vessels, but is pumped into a hemocoel, which circulates around the organs, then reenters the heart through ostia. It is less controlled and structured than an open circulatory system, but nutrients and waste products are transported more efficiently.
  4. Blood in a closed circulatory system is present inside blood vessels, circulates unidirectional from heart around the systemic circulatory route, and then returns to the heart. It is more structured, controlled, and nutrients and waste products are transported more efficiently than in open circulatory system.
25 .
What is one advantage of a four chambered heart over a three chambered heart?
  1. Oxygenated blood carried by the right side of the heart is completely separated from the left side carrying deoxygenated blood, which assists in more efficient movement of oxygen around the body and aids in allowing the body to quickly move when needed.
  2. A four-chambered heart keeps oxygenated and deoxygenated blood separated and has double circulation whereas a three-chambered heart has a single circulation. This assists in more efficient movement of oxygen around the body.
  3. Oxygenated and deoxygenated blood are kept separate in a four-chambered heart, which assists in more efficient movement of carbon dioxide around the body.
  4. Oxygenated and deoxygenated blood are kept separate in a four-chambered heart, which assists in more efficient movement of oxygen around the body and aids in allowing the body to move quickly when needed.
26 .
What are red blood cells also known as?
  1. lymphocytes
  2. monocytes
  3. erythrocytes
  4. basophils
27 .
How does the structure of red blood cells allow them to deliver oxygen to the cells of the body?
  1. Their size and shape allow them to carry and transfer oxygen.
  2. Their disc shape contains many small vesicles that allow them to carry and transfer oxygen.
  3. They have nuclei and do not contain hemoglobin.
  4. They contain coagulation factors and antibodies.
28 .
Which of the following best describes plasma?
  1. It is a protein synthesized in the liver.
  2. It is a liquid that contains only lipids and antibodies.
  3. It is a blood component that is separated by spinning blood.
  4. It is an antibody produced in the mucosal lining.
29 .
What is the heart’s internal pacemaker?
  1. An internal implant sends an electrical impulse through the heart.
  2. It is an electrical impulse that starts in cardiac muscle cells at the sinoatrial node.
  3. It is the excitation of cardiac muscle cells at the atrioventricular node followed by the sinoatrial node.
  4. It starts in the aorta.
30 .
Cardiomyocytes are similar to skeletal muscle because they _______.
  1. beat involuntarily
  2. are attached to bones
  3. pulse rhythmically
  4. are striated
31 .

The diagram shows the internal anatomy of the heart. How would blood circulation beyond the heart be affected if the pulmonary valve could not open?

  1. Blood could not reach the rest of the body.
  2. Blood could not reach the lungs.
  3. Blood could not return from the lungs.
  4. Blood could not return from the rest of the body.
32 .

The diagram below shows the internal anatomy of the heart. How would blood circulation beyond the heart be affected if the tricuspid valve could not open?

  1. Blood could not enter the pulmonary veins; therefore, it could not reach the lungs.
  2. Blood could not enter the pulmonary artery; therefore, it could not reach the heart.
  3. Blood could not enter the pulmonary artery; therefore, it could not reach the lungs.
  4. Blood could not enter the pulmonary veins; therefore, it could not reach the heart.
33 .
Why is it useful for blood to travel slowly through capillary beds?
  1. To allow antibodies to enter infected cells and to promote the diffusion of fluid into the interstitial space.
  2. To assist with gas and nutrient exchange and to prevent the diffusion of fluid into the interstitial space.
  3. To assist with gas and nutrient exchange and to promote the diffusion of fluid into the interstitial space.
  4. To allow antibodies to enter infected cells and to prevent the diffusion of fluid into the interstitial space.
PreviousNext
Order a print copy
Citation/Attribution
Reuse and redistribution of this content in digital or print format:
  • This book may not be used in the training of large language models or otherwise be ingested into large language models or generative AI offerings without OpenStax's prior written permission.
  • This book uses the Creative Commons Attribution-NonCommercial-ShareAlike License, which means that you can reuse and modify the material only for noncommercial purposes, must attribute OpenStax, and must distribute any derivative works under the same license.
  • Any commercial printing of this textbook, including using a local or custom printer, must be approved by OpenStax, and proper citation provided.
  • OpenStax-copyrighted images, activities, assessments, and similar components of this book are subject to the same licensing – CC-BY-NC-SA. They can be used for noncommercial purposes with attribution. Commercial use requires permission.
  • Permission requests: Anyone who intends to incorporate this content (including text, images, and other components) into large language models, use it in AI offerings, use it commercially (including in print), and/or has questions about another use case is welcome to complete our reuse request form.
Attribution information
  • If you are redistributing all or part of this book in a noncommercial print format, then you must include on every physical page the following attribution:

    Access for free at https://openstax.org/books/biology-ap-courses/pages/1-introduction

  • If you are redistributing all or part of this book in a noncommercial digital format, then for every page that includes OpenStax content, you must license the derivative work under the same CC-BY-NC-SA license as the original, and include on every digital page view the following attribution:

    Access for free at https://openstax.org/books/biology-ap-courses/pages/1-introduction

Citation information

The information below includes the information needed to generate citations in most major styles (APA, MLA, etc.); you must reformat and organize the information as needed to fit the requirements of the style. Use the information below to generate a citation. We recommend using a citation tool such as this one.

© Jul 22, 2026 OpenStax. Textbook content produced by OpenStax is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike License. The OpenStax name, OpenStax logo, OpenStax book covers, OpenStax CNX name, and OpenStax CNX logo, and Rice University name, and Rice University logo trademarks, or wordmarks are not subject to the Creative Commons license and may not be reproduced without the prior and express written consent of Rice University.