Question

Please solve my Science doubts:
i) How expansion and contraction happens in guard cells?
ii) I read this in my Science textbook: "In Amoeba, exchange of gases takes place by DIFFUSION through CELL MEMBRANE. " Can you explain me that what is 'diffusion' when we talk about respiration?
iii) What is 'Pharynx'?
iv) What is 'muscle cramp'?
v) Why do we yawn when we feel sleepy?
vi) What is 'Larynx'? 
I'm in class 7th. These are my Science doubts related to chapter 'Respiration'. Please solve all my six doubts. This is my humble request.

Answer 1

contraction amd relaxation occurs due to difference in wall thickening
pharynx is the place just beside the buccal cavity
muscle cramp means pain in caused
due to formation of lactic acid
larynx is a box like structure in wind pipe which is callwd voice box due to vibration in it we able to speak