In mammals and birds, it is necessary to flow blood through arteries and veins separately, as it allows oxygenated and deoxygenated blood to flow.

Explanation:

• Usually, arteries are meant for carrying the blood away from the heart. Veins will carry the blood back to the heart.
• The mammals and the birds have a double circulatory system, as it allows oxygenated and deoxygenated blood to flow separately from each other within the heart.
• This double circulatory system enables higher metabolic rates to be maintained, as oxygenated and deoxygenated should not get mixed.
• The blood leaving the heart is rich in oxygen content, which in turn is essential for birds and mammals.

To know more about circulatory system,

1) Why is the circulatory system important to the body?

brainly.in/question/12855922

2) What is the difference between human circulatory system and human transportation

brainly.in/question/8239613