What you’ll learn4 learning objectivesChoose one objective for a focused lesson, or study the complete topic.9.1.1Circulatory system as a system• Describe the circulatory system as a system of blood vessels with a pump and valves to ensure one-way flow of bloodSyllabus objective9.1.2Single circulation of a fish• Describe the single circulation of a fishSyllabus objective9.1.3Double circulation of a mammal• Describe the double circulation of a mammalSyllabus objective9.1.4Advantages of a double circulation• Explain the advantages of a double circulationSyllabus objective