Chapter 21. Chapter 21: Circulation and Respiration

Review & Rehearse
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You must read each slide, and complete any questions on the slide, in sequence.

Instructions

Review the visual summaries and answer the essay questions below.

Make sure to enter a brief response that completely answers each question and explains your reasoning. When you click "Submit," you will be provided instant feedback, allowing you to check if your response is correct.

(This activity contains 18 total essay questions. Each new question will be revealed once you complete the preceding question.)

1.

1. Why has the evolution of multicellular organisms led to the development of circulatory systems?

With the increasing size of multicellular organisms, most of an organism’s cells are not in direct contact with the external environment, so essential nutrients and wastes cannot diffuse into and out of cells adequately. A dedicated delivery and removal system (a circulatory system) is necessary.

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