Ecology: 02 Sampling Techniques

Ecology: 02 Sampling Techniques



all right so here we are with video 2 we're gonna talk about sampling techniques now as an ecologist you're going to want to know how many of each organisms are there and you know the animals around you and you might have a very large area to count yet so we use sampling techniques as a way to estimate as best we can alright so basically why do we do it one pathology requires us to know how many of everything is there okay it's just you need to know what makes up your community before you can really talk about it too much detail now it's way too time-consuming to count every single one or it's impossible depending on what it is you're dealing with so we have samples to estimate the size for example over here with our actual population they've collected a bunch of their sample they can use that to estimate what's in there now it may not be very accurate or may be super accurate depending on but basically there are various techniques for different purposes so we've got one the two way of the folks on one is really good for plants and things that don't move around and other is really good for things like to run away from you all right so I simply must be it must have these two characteristics it must be random okay this reduces the bias this is really really important with all science like it but it must be random and it must be representative so you need a large enough sample to improve the accuracy so you want roughly 10% of the population that's close you can't get to 10% anyway and you want at least 10% of the area covered now again not always possible but this is something you talk about with regards to your discussion and also stuff when you write it up all right some quadrats you know really useful for stationary Owens like plants fungus boss etc you basically you measure the total area of the population I throw the area where the population lives I take a square there's a quadrat depending what it is it could be a one by one meter square like this or you could divide the whole area up into grids they say other way was there second you randomly throw it so if you've got this or you randomly just read we choose the squares that you're going to look at and count and you count the number of organisms within that square and you repeat that as many times as is practical then you average that revolve it as per quadrat and you multiply this up to the size of the area and that tells you roughly how many of those plants boss whatever is it that that area that you're looking at so here are the two ways to do it you've got your squares and you strung out there now if you've got 100 meters by 2 meters that's probably enough is this so you here your squares and you just randomly assign them now you would do this weird if you're looking at large so these would be five the grasses and shrubs little things that you could fit inside square that you can throw this one would be most effective over here this will be most effective when you're talking about trees so really be quite throw it high enough to get it over to Joe you've linked all right capture release mobile organisms so it's often it's not reasonable to count every individual in the population okay so first you want to capture as humanely as possible a lot as large a sample as possible you then want to tag those captured and rerelease them so take those captured and release given that debuted so tag the set of three you'll to capture a second sample this is important okay you want to count the number already tagged we're gonna kill those recaptures and they actually fits it to this circle here I think you use this formula so the first capture times the second capture divided by captures that tells you roughly how many you have okay so we'll look through that here we have an example so first capture is taking captured times recap / recaptures or n1 times F 2 2 divided by 3 so this case before 8 captured eight recaptured two of those were so I captured the set capture two of those recaptures this gives us 32 okay now if you do the math we're at about 24 here okay so it's actually not that accurate but it's not perfectly if it's not bid to me it's an estimation the larger the sample size the more the actress the higher the levels of accuracy all right so that's sampling and we'll practice some of these techniques most likely they capture recapture you Class C

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