OCR A LEVEL BIOLOGY TRANSPORT IN ANIMALS QUESTION AND CORRECT ANSWERS GRADED A+

OCR A LEVEL BIOLOGY TRANSPORT IN ANIMALS
QUESTIONS WITHCORRECT ANSWERS RATED A+
QUESTION
Why do multicellular animals need transport systems?

CORRECT ANSWER
Multicellular animals have a high metabolic rate, meaning they require large amounts of oxygen
and nutrients and produce large amounts of waste. Diffusion alone is too slow over long
distances. They also have a small surface area to volume (SA:V) ratio, resulting in longer
diffusion distances and insufficient exchange by diffusion alone.



QUESTION
What is a closed circulatory system?

CORRECT ANSWER
A closed circulatory system is one in which blood is enclosed within blood vessels and does not
come into direct contact with all body cells. The heart pumps blood under pressure, and
substances enter and leave the blood through blood vessel walls. Blood flow to tissues can be
adjusted by vasodilation and vasoconstriction.



QUESTION
Why is a closed circulatory system effective in multicellular mammals?

CORRECT ANSWER
It allows blood to travel rapidly under high pressure to wherever it is needed, ensuring efficient
delivery of oxygen and nutrients to meet high metabolic demands.



QUESTION
What is a single closed circulatory system?

CORRECT ANSWER
In a single closed circulatory system, blood passes through the heart once per complete circuit
and through two sets of capillaries before returning to the heart. The first set allows gas
exchange, and the second allows exchange between blood and body tissues.

, QUESTION
Why is metabolic activity relatively low in most animals with a single closed circulatory system?

CORRECT ANSWER
Blood pressure drops significantly after passing through the first capillary bed, meaning blood
returns slowly to the heart. This reduces the efficiency of exchange, limiting metabolic activity.



QUESTION
Most animals with a closed circulatory system have low metabolic activity. Why are fish the
exception?

CORRECT ANSWER
Fish have a counter-current exchange system in their gills. Water with a high oxygen
concentration flows in the opposite direction to blood with a low oxygen concentration,
maintaining a constant concentration gradient and allowing very efficient oxygen uptake.



QUESTION
What is a double closed circulatory system?

CORRECT ANSWER
In a double closed circulatory system, blood completes two circuits. Blood travels from the
heart to the lungs for gas exchange, returns to the heart, and is then pumped to the rest of the
body before returning again to the heart.



QUESTION
What is an open circulatory system in insects?

CORRECT ANSWER
In insects, blood (haemolymph) flows freely into the body cavity (haemocoel) at low pressure. It
does not transport oxygen or carbon dioxide, which are delivered via spiracles and tracheae,
but it does transport nutrients, waste products, and immune cells.



QUESTION
What are the main functions of blood?