[Music] hi and welcome back to free science lessons by the end of this video you should be able to describe sampling techniques used in biology now in the video on biodiversity we looked at the idea of species richness and species evenness in order to determine these we need to be able to sample the organisms within a habitat we're going to start by looking at how to sample animals imagine that we wanted to sample the insects present in a field of plants such as this Meadow one technique is to use a sweeping net which I'm showing you here the sweeping net is swept over the plants multiple times and this traps any insects present we can catch small insects directly by using a puta a puta consists of a container with two tubes the trapping tube is placed near the insect that we want to catch we place the mouthpiece tube in our mouth and gently inhale the insect is now sucked into the trapping tube and into the container the mouthpiece tube has a piece of cloth to stop any insects from being sucked into the mouth if we want to trap ground level animals such as insects or snails then we can use a pitfall trap like the one I'm showing here a pitfall trap is a container sunk into the ground over the Trap we place a cover which prevents rainwater from entering ground level animals fall into the Trap which is deep enough to stop them from crawling out if we want to sample the tiny animals present in the soil then we can use a tolgren funnel which I'm showing you here the soil sample is placed in a funnel above a container and a light bulb gently heats the surface of the soil the animals in the soil move downwards away from the Heat once the animals reach the bottom of the funnel they fall into the container kick sumpling is used to sample the bottom dwelling animals living in a riverbed a net is placed Downstream and the scientist gently kicks the riverbed to dislodge any rocks or Pebbles any organisms which are Disturbed move Downstream and are caught in the net now if we're sampling slow moving or static animals for example on a seashore then we can use a frame quadrat like this a flame quadrat is simply placed on the ground and any animals within the quadrat are sampled we can also use a frame Quadra to sample the plants in a habitat imagine that we're using a quadrat which is one meter squared if we count the actual number of a plant species for example dandelions then the number we count is called the density per meter squared this is a highly accurate sampling method some plants are difficult to count for example Moss or we may have a plant with a very large number such as grass in these cases we look at how many small squares within the quadrat contain the plant we then report this number as the percentage frequency the quadrat I'm showing you here contains 100 small squares if Moss was found in 20 of the squares then the frequency of moss is 20 percent notice that we're not trying to determine how much of each square is covered by Moss we're simply saying this percentage of small squares contain Moss now if a plant occupies a large proportion of the quadrat then we can use percentage cover in this case we simply estimate by I what percentage of the total quadrat area is occupied by the plant percentage cover is a very Rapid Way of sampling but it's the least accurate method in all cases we can increase reliability by placing the quadrat in multiple positions and calculating a mean now instead of using a frame quadrat we can use a point quadrat a point quadrat is a wooden bar with holes in it we position the bar over the ground and place metal pins into each hole we count any plant which is touched by the PIN okay so hopefully now you can describe sampling techniques used in biology foreign [Music]