Gas Exhange 3.3.2(Organisms exchange substances with their environment 3.4)

Question 1

What are some adaptations for exchange in animals?

Answer 1

• Large surface area
• Thin membrane for short pathway of substances
• Good blood supply / ventilation to maintain a steep gradient

Question 2

EQ : Explain how blood in a vein in the leg is returned to the heart (6)

Answer 2

1) Muscles contract and press on vein and squeezes blood along vein
2) Valves prevent back flow of blood
3) Systole through arteries into veins , negative pressure in chest due to inspiration
4) Recoil of heart muscle during diastole .
5) Draws blood from veins into atria
6) Wide lumen little friction

Question 3

EQ :
The valves between the atria and ventricles are closed between 0.1s and 0.4s .
Explain how pressure causes these valves to be shut (1)

Answer 3

Higher pressure in systole of ventricle than atria

Question 4

EQ : Explain how closure of valves is essential to the functioning of the heart (1)

Answer 4

Prevents back flow of blood so the heart is constantly pumping blood