1.2 investigating populations

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A-Level A2 BIOL4 (1. populations ) Flashcards on 1.2 investigating populations, created by Charlotte Hewson on 08/03/2016.
Charlotte Hewson
Flashcards by Charlotte Hewson, updated more than 1 year ago
Charlotte Hewson
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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