CAX IGCSE Biol Why have a heart and surface area

How do you calculate surface area to volume ratio?

• Surface area / volume

• Surface area - volume

• Surface area + volume

Why is there a limit to cell size in multicellular organisms?

• As size of cells increase, their surface area to volume ratio also increases meaning substances would diffuse too slowly into the cell.

• As size of cells increase, their volume decreases meaning substances would diffuse too slowly into the cell.

• As size of cells increase, their surface area to volume ratio decreases meaning substances would diffuse too slowly into the cell.

List the structures in the circulatory system the blood travels through from vena cava to aorta.

• Vena cava, lungs, pulmonary vein, left atrium, left ventricle, aorta, right atrium, right ventricle, pulmonary artery,

• Vena cava, left atrium, right ventricle, pulmonary vein lungs, pulmonary artery, right atrium, left ventricle, aorta

• Vena cava, right atrium, right ventricle, pulmonary artery, lungs, pulmonary vein, left atrium, left ventricle, aorta

What are the differences between anaerobic and aerobic respiration?

• Anaerobic respiration takes place in mitochondria, releases less energy and forms lactic acid that causes cramp. Aerobic respiration occurs in cytoplasm, releases more energy and forms carbon dioxide and water which do not cause cramp.

• Anaerobic respiration takes place in cytoplasm, releases less energy and forms lactic acid that causes cramp. Aerobic respiration occurs in mitochondria, releases more energy and forms carbon dioxide and water which do not cause cramp.

• Anaerobic respiration takes place in cytoplasm, releases less energy and does not cause cramp. Aerobic respiration occurs in mitochondria, releases more energy and causes cramp.

Which of the following statements about diffusion rate is incorrect?

• If surface area is doubled, the rate of diffusion is doubled

• If concentration gradient is halved, the rate of diffusion is halved

• If diffusion distance is tripled, the rate of diffusion is tripled

• If diffusion distance is increased by 20%, the rate of diffusion is reduced by 20%

If a cube has sides that are 2cm in length, what is the surface area to volume ratio of the cube?

• 16:8

• 3:1

• 4:8

• 36:8

As the size of an organism increases, the surface area to volume ratio...

• Increases

• Stays the same

• Decreases

• Doubles

Which of the following statements explains why carbon dioxide diffuses into the alveolus from the blood?

• The concentration of carbon dioxide is higher in the alveolus than in the blood

• The concentration of carbon dioxide is same in the alveolus and in the blood

• The concentration of carbon dioxide is higher in the blood than in the alveolus

• Oxygen diffusing into the blood from the alveolus takes the place of carbon dioxide when it binds to haemoglobin

Which of these unicellular organisms have a circulatory system?

• Euglena

• Amoeba

• Paramecium

• non of the above

Large animals can not use diffusion because.....

• They have a large surface area to volume ratio

• Diffusion distance from the environment to the respiring cells is to far, and so would be too slow.

• Diffusion distance is close, so is adequate.

• The do not use much oxygen so do not use diffusion, but use a circulatory system.