gas exchange with plants and stuff

Question 1

Describe how gas exchange occurs in single-celled organisms and explain why this method cannot be used by large, multicellular organisms. [3 marks]

Answer 1

by diffusion across thee cell membrane
smaller organisms have a larger surface area: volume ratio
larger organisms have a smaller surface are: volume ratio.
so diffusion pathway is longer in larger organisms

Question 2

Describe how gas exchange occurs in single-celled organisms and explain why this method cannot be used by large, multicellular organisms. [3 marks]

Answer 2

external intercostal muscles contract and the ribcage is pulled up
diaphragm contracts and is pulled down
causes the volume to increase and the pressure to decrease in the thoracic cavity

Question 3

state three control variables in that ager pratical

Answer 3

the temperature
the pH of the acid
the concentration of the acid

Question 4

Explain the importance of one adaptation of the gas exchange surface in the tracheal system of an insect.

Answer 4

-the tracheole is one cell thick so short diffusion pathway to cells.
- tracheoles enter muscle fibres so diffusion is rapid
- tracheoles are highly branched so large surface are for rapid diffusion

Question 5

Explain the importance of the xylem being kept open as a continuous tube. 3 marks

Answer 5

• allows unbroken water column
• there is cohesion from the polar attraction between the water molecules.
• evaporation creates tension in column

Question 6

what polymer is found within the walls of the xylem

Answer 6

lignin