circulatory systems

Question 1

Why do multicellular organisms need a circulatory system? (2)

Answer 1

Multicellular organisms have a low surface area to volume ratio, high metabolic rate, and are often very active

They need a constant, rapid supply of oxygen and glucose, which is provided by the circulatory system using blood

Question 2

What are the two different types of circulatory systems? (2)

Answer 2

Open circulatory system (e.g., insects)

Closed circulatory system (e.g., fish and mammals)

Question 3

Describe open circulatory systems (5)

Answer 3

Blood flows freely through the body cavity

The heart pumps blood into a main artery

Which opens into the body cavity

Where it flows around organs and re-enters the heart through valves

Does not transport oxygen (tracheal system does this)

Question 4

Describe closed circulatory systems (3)

Answer 4

Blood is always confined to blood vessels

Heart pumps blood into arteries, which branch into capillaries

Oxygen and nutrients diffuse into cells, and veins return blood to the heart

Question 5

What is the difference between a single and a double circulatory system? (2)

Answer 5

Single circulatory system (e.g. fish) = Blood passes through the heart once per circuit

Double circulatory system (e.g. mammals) = Blood passes through the heart twice per circuit (pulmonary and systemic systems)

Question 6

What is the advantage of double circulatory systems? (2)

Answer 6

Heart gives the blood an extra push between the lungs and the rest of the body

Making O2 delivery faster