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Description
Flashcards by Charlotte Hewson, updated more than 1 year ago
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Created by Charlotte Hewson
over 8 years ago
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| Question | Answer |
| what is abundance? | the number of individuals of a species in a given space |
| what are the two sampling techniques? | random sampling using quadrats or point quadrats |
| what are the three factors to consider when using quadrats? | the size - depends on size of organism and their distribution number of samples - more = more reliable position of quadrat - random to produce statistically significant results. |
| why must sampling be random? | to avoid bias and give valid data. |
| what is the method of random sampling? | 1) lay out 2 tape measures at right angles along 2 sides of the study area 2) obtain coordinates by using a random number generator/table 3) place a quadrat at the intersection of each pair of coordinates and record species within. |
| when is systematic sampling better? | when there is a transition in the communities present. |
| What method shows the stages of zonation? | transects |
| how does a line transect work? | a string or tape stretched along the ground in a straight line, any organism it passes over is recorded. can also be done as a belt transect across 1m |
| what are two ways to measure abundance? | frequency percentage cover |
| what is good about using frequency? | useful when species is hard to count e.g. grass gives a quick idea of species present and their general distribution |
| what is bad about using frequency to measure abundance? | no info on density or details of distribution |
| what is good about using percentage cover? | useful when species is particularly abundant/difficult to count rapid collection of data |
| when is percentage cover less useful? | when organisms occur in several overlapping layers |
| what is the process of this technique? | animals caught, counted, marked and released. some time later, more are collected randomly and counted, and number of marked is recorded. |
| how do you calculate the size of a population? | |
| what does this technique assume? | - proportion of marked to unmarked is same in sample as population. - marked distribute in given time - population has boundary, no migration - few if any births/deaths -marking doesn't affect survival - mark not lost/removed |
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