Tadpoles dying

[Wai]

Hello all,

 

I just started doing Year 12 biology at school, but I'm already stuck with a few questions which I can't answers for in the text book.

 

1. Explain why tadpoles living in a puddle of water may die well before the water has completely dried up.

 

2. Chloroform and ether quickly induce unconsciousness. What chemical property do they have which explains their rapid absorption and thus rapid effect?

 

3. If a drowning person inhales fresh water into their lungs, death occurs rapidly in about three minutes. If a drowning person inhales sea water instead of fresh water, death occurs more slowly taking about six to eight minutes. Use your understanding of osmosis to explain the difference between inhaling fresh water and sea water. You will need to consider the relative salt concentrations of sea water (1100 mOsm), blood (300 mOsm) and fresh water (0 mOsm).

 

I have searched everywhere but haven't found any specific answers. Could anyone help me with these?

 

Thanks

[SkepticLance]

Question 1.

 

I do not really know the answer. Could be the concentrating of solutes due to water evaporation, or more likely, the fact that the small body of water heats up and loses oxygen.

 

Question 2.

 

Chloroform and ether are taken into the blood via the lungs. Transport from lungs to brain is exceedingly fast - a matter of a very few seconds. The brain is mostly fat, and these are cheicals that dissolve in fat. They are taken up into the fatty tissue of the brain very quickly and have their impact. hence rapid unconsciousness.

 

Question 3.

 

A misleading question. Drowning normally occurs due to a type of gag reflex which is exactly the same whatever the water, and results in unconsciousness and later death from asphyxiation. Complete time to final death is about the same.

 

However, the questioner is assuming the victim inhales water and dies from the effect of water rather than asphyxiation. Fresh water is absorbed into lung tissue due to osmosis and causes local damage from tissue swelling. If the victim is revived, he/she may later succomb due to this damage interfering with normal lung function. This is due to damaged lung tissue 'weeping' fluid into the alveoli. This is less likely with salt water, since it is close to isotonic with body fluids, and the osmosis is less, and occurs in the reverse direction.

[Wai]

Ah. I'll keep searching for answers to the tadpole one. I was just a little surprised that there would be quite a number of questions that required extra research. Thanks bunches!