How do you calculate Total Estimated Population and Species Density?

Question

I need your help fast. It's for an assignment I have to finish tonight and I've lost my book with the calculations!

Answer 1

Estimated density refers to an indirect method which means you don't count all directly. There are 2 methods. 1. Quadrant method. Divide the area you want to cover in equal sized blocks( eg. 20). Then count your selected organisms (eg. snails) only in some of the blocks (eg. 10 blocks). If you have counted 50 snails in these ten block, thus an average of  5 snails per block.In total there are 20 blocks with thus 5 snails per block giving you a total of 20 x 5 = 100 snails in the whole area.

2. Mark and recapture method. To count no. of antelope in a game reserve.  Catch 10 animals and mark them  (M). Release them back into their environment and give them enough time to move back into their area. Then do a second capture(S) (must be more than M) eg. 20.

Now count how many of these 20 are marked (T) .  Then use the formula: Population density =( MxS) / T