A level Biology Unit 3 AQA

Which of these factors will have the least affect on the rate of diffusion of substances into cells?

• Thickness of cell surface membrane.

• Cell surface area.

• Permeability of membrane to the substance.

• The volume of the cytoplasm.

Name the process in which carbon dioxide is removed from single celled organisms

• Facilitated diffusion

• Breathing

• Diffusion

• Active transport

The blue whale is the largest organism on the planet. It spends much of it's life in very cold waters. Why is a large size an advantage to a blue whale?

• It has a very large surface area to volume ratio and so loses less heat too the water.
• It has a very small surface area to volume ratio and so loses less heat to the water.

Why is there a conflict in terrestrial insects between gas exchange and conserving water?

• Gas exchange requires a thin permeable surface with large surface area. Conserving water requires thick waterproof surfaces with a small area.
• Gas exchange requires a thick waterproof surface with a small area. Conserving water requires a thin permeable surface with large surface area.

Explain how tracheal systems limit the size of insects.

• Insects don't eat enough to allow active transport to take place over long distances.
• Insect trachea contain water.
• Insects have small lungs.
• Insects rely on diffusion to get oxygen to the working muscles. Diffusion is slow over large distances

In relation to fish gills, what is meant by countercurrent flow?

• The movement of water and blood in opposite directions across gill lamellae.
• The movement of water and blood in the same direction across gill lamellae.

Describe what happens to the concentration of oxygen in insect tracheae when spiracles are closed.

• It increases
• It decreases

Why do insects close their spiracles?

• To reduce loss of oxygen.
• To reduce loss of carbon dioxide.
• To reduce loss of water.

Why is countercurrent flow an efficient mechanism for exchanging gases across the gills of fish?

• High oxygen water comes into contact with low oxygen blood increasing diffusion rate
• High oxygen water comes into contact with high oxyen blood first, maintaining a steady diffusion gradient.

Which of these is not an adaptaion of xerophytic plants?

• Hairy leaves
• Stomata in pits
• Raised stomata
• Curled leaves