All known birds and mammals have __________.

• A. a single circulatory system and a four-chambered heart
• B. a double circulatory system and a three-chambered heart
• C. a double circulatory system and a two-chambered heart
• D. a single circulatory system and a two-chambered heart
• E. a double circulatory system and a four-chambered heart

Answer: (E)

Verified step by step guidance

1. Understand the concept of circulatory systems: In biology, a circulatory system is responsible for transporting blood and nutrients throughout the body. There are two main types: single and double circulatory systems.
2. Define a single circulatory system: In a single circulatory system, blood passes through the heart once during each complete circuit of the body. This type is typically found in fish.
3. Define a double circulatory system: In a double circulatory system, blood passes through the heart twice during each complete circuit. This system is more efficient and is found in birds and mammals.
4. Understand heart chambers: The heart can have different numbers of chambers. Fish typically have two chambers, amphibians and reptiles often have three, while birds and mammals have four chambers.
5. Combine the concepts: Birds and mammals have a double circulatory system, which allows for efficient oxygenation of blood, and a four-chambered heart, which separates oxygenated and deoxygenated blood, enhancing the efficiency of the circulatory system.