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This guide explores various techniques for measuring populations of organisms in different environments. Direct observation involves counting organisms individually, as in counting trees in a forest. Indirect observation estimates populations based on signs, such as finding roots in a mine suggesting nearby trees. Sampling involves multiplying the count of a smaller group to estimate a whole population, like zebras in a family. The mark-and-recapture method records and releases animals to gauge species numbers, exemplified by marking bees and estimating their total based on catches.
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Measuring Populations By: bakt, henn, zart
Direct Observation • Counting organisms one by one in person or photograph. • Ex. We went to the forest and counted all the trees.
Indirect Observation • Finding signs of organisms when you can’t actually see the organisms, then estimating from those signs how many of those organisms there are in that area. • Ex. We went into the mines and found a roof full of roots so we figured out that there were a lot of trees above.
Sampling • Find the smaller number, then multiply it to make it a whole population. Instead of just a small proportion. • We found a family of zebras and multiplied how many were in that family by ten.
Mark and Recapture • When you mark an animal you have caught, then let them back into their habitat. Then you go to the same area and catch more of those animals, and count how many of them aren’t marked. Then you can do math to figure out how many of that species are in that area. • We caught bees and dotted their wings, then caught more again and saw how many of them weren’t dotted.
