Sampling Techniques and Measurements National 5 Sampling Techniques and Measurements Mr G Davidson

Sampling an Ecosystem We would sample an ecosystem to: Find out which organisms live in it. Find the abundance (how many) of these organisms. Find out why these organisms live in this ecosystem. Thursday, 15 November 2018 Mr G Davidson

Sampling an Ecosystem When we are trying to find out the abundance of organisms, it is almost impossible to count every single individual, and so we take small samples. In order to ensure this is valid, each sample area must be the same size. We would take a number of samples to provide us with data to calculate the average. Thursday, 15 November 2018 Mr G Davidson

Using a Quadrat In order to sample plants (and slow moving animals) we can use a quadrat. A quadrat marks off a small piece of ground of known area so that different plants present within this sample can be identified and counted or their area of cover estimated. This sample gives us an idea of the number and kind of organism present in the whole area. 15 November 2018 G Davidson

Using a Quadrat The quadrats we use are 0.25m2 and sub-divided into 25 smaller squares each 100cm2. The quadrat is placed randomly on the ground. The number of small squares containing the plant we are interested in are counted. This is called the abundance estimate. 15 November 2018 G Davidson

Estimating Total Numbers We can estimate the total numbers of organisms living in a certain area. We need to calculate the area we are sampling. 15 November 2018 G Davidson

Estimating Total Numbers We need to estimate numbers using the quadrat. We then calculate an average number of organisms per quadrat. We then work out how many quadrats fit into the specified area and multiply this number by the average number of organisms per quadrat. 15 November 2018 G Davidson

Estimating Total Numbers Calculate the area of this field. Length times breadth. 15m 40m 15 November 2018 G Davidson

Estimating Total Numbers We now know the area of the field is: 15 x 40 = 600m2. We now need to sample the field by using the quadrat , say 10 times. The quadrat is then placed randomly in 10 different spots in the field, and the number of plants counted. Suppose we are measuring daisies. 15 November 2018 G Davidson

Sampling Daisies The quadrats are placed randomly and the number of daisies in each are counted. 15m 40m 15 November 2018 G Davidson

Sampling Daisies The results are collected and recorded. We then calculate the average number of daisies per quadrat. Add up the number of daisies column and divide by the number of sites. Quadrat Number of daisies 1 7 2 15 3 9 4 5 12 6 13 8 10 16 15 November 2018 G Davidson

Sampling Daisies In this case the total number of daisies sampled was 90. The number of sites was 10. Therefore the average number of daisies per site is 90 ÷ 10 = 9 daisies We now need to work out how many quadrats fit the field. 15 November 2018 G Davidson

Sampling Daisies The field is 600m2 and there are 4 quadrats to each 1m2. Therefore, the field is 600 x 4 = 2400 quadrats. If there are, on average 9 daisies per quadrat, this means there are 9 x 2400 = 21 600 daisies in the field. A good estimate. 15 November 2018 G Davidson

Estimating Total Numbers Here is one for you to try on your own. This time we are estimating the number of worms in a field. Here are the results. Quadrat No. of Worms 1 6 2 7 3 4 9 5 12 8 10 15 November 2018 G Davidson

Estimating Total Numbers 15 November 2018 G Davidson

How did you do? Average number of worms per quadrat? Answer – 7 worms per quadrat. Total area of field? Answer – (50 x 40) – (25 x 15) = 1625m2 Total number of quadrats in field? Answer - 1625 x 4 = 6500 quadrats Total number of worms? Answer – 6500 x 7 = 45 500 worms 15 November 2018 G Davidson

Sources of Error When using quadrats, there are a number of mistakes which can be made. Organisms wrongly counted. Organisms wrongly identified. Is it in the quadrat or not? Number of samples too small. Thursday, 15 November 2018 Mr G Davidson

Sources of Error We can minimise these errors in a number of ways. Take a large number of samples and calculate averages. This helps to make the results more reliable. A key can be used to identify the correct organisms. Have a rule to determine whether an organism is classed as in the quadrat or out, and stick to it for all quadrats. Thursday, 15 November 2018 Mr G Davidson

Other sampling Techniques Pitfall traps are used to trap small animals moving across the surface of the ground. 15 November 2018 G Davidson

Pitfall Trap 15 November 2018 G Davidson

Sources of Error Organisms in the trap may be eaten. Cover the trap with a lid to try to keep predators from seeing them. Some animals in the trap may eat others in the trap. Either check the traps on a regular basis or put 50% ethanol in the trap to kill all animals and preserve them. Thursday, 15 November 2018 Mr G Davidson

Other Sampling Techniques Sweep netting is used to catch small animals living in vegetation. Potato traps can be used to attract small animals, particularly snails and slugs. Tree beating is used to remove organisms from branches. Thursday, 15 November 2018 Mr G Davidson

Pond nets are used to catch animals living in ponds. 15 November 2018 G Davidson

Tullgren funnels are used to remove tiny organisms from soil samples. 15 November 2018 G Davidson

Pooter Pooters are used to capture small insects. 15 November 2018 G Davidson

Measurement of Abiotic Factors Abiotic factors are non-living. They tend to be climate related. Light intensity can affect the distribution of organisms. Some plants require very sunny conditions and others can survive in shady conditions. Thursday, 15 November 2018 Mr G Davidson

Measuring Light Intensity We can measure light using a Light meter. Make sure you don’t cast a shadow on the meter or you will get a false reading. Take a number of readings to calculate an average. 15 November 2018 G Davidson

Measuring Moisture We can measure moisture using a moisture meter. Carefully push the probe vertically into the soil to a depth of approximately 4cm. 15 November 2018 G Davidson

Measuring pH We measure soil pH using a pH meter. Carefully push the probe vertically into the soil to a depth of approximately 4cm. Make sure the probe is cleaned between samples. 15 November 2018 G Davidson

Measuring Temperature Soil temperature is measured using a soil thermometer. The thermometer is pushed gently into the soil and left to settle, before a reading is taken. Thursday, 15 November 2018 Mr G Davidson

Reducing Errors It is important to try to reduce all possible sources of error, e.g. Don’t hold the bulb of the thermometer. Make sure the bulb is down into the soil. Take a number of readings to get an average. Thursday, 15 November 2018 Mr G Davidson

Identifying Organisms It’s all very well counting organisms or collecting organisms. Not all of them will be familiar to us. In order to identify unfamiliar organisms, we would use a key. There are different kinds of key. We will use 2 kinds. Branching Keys Paired statement keys. 15 November 2018 G Davidson

Branching Keys These are pictorial. At each stage you are given a choice of two things. You pick the most appropriate and move to the next choice. Eventually you should be left with the name of your organism. Thursday, 15 November 2018 Mr G Davidson

Branching Keys Animals Legs No Legs More than 8 Legs 8 Legs Shell No Shell Spider Centipede Snail Earthworm Thursday, 15 November 2018 Mr G Davidson

Paired Statement Keys Paired statement keys work in the same way as branching keys. At each stage you are given a choice. Make the appropriate choice and go to where you are asked to go. Again, if the organism is present, you should end up with a name for it. 15 November 2018 G Davidson

Paired Statement Key Single leaf go to 2 Several leaflets go to 6 2. Leaf with prickles HOLLY Leaf with no prickles go to 3 3. Leaf edge with lobes go to 4 Leaf edge with no lobes go to 5 4. Lobes sharp pointed SYCAMORE Lobes rounded OAK 5. Leaf with smooth edge BEECH Leaf with serrated edge ELM 6. Leaflets in fan shape HORSE CHESTNUT Leaflets in pairs go to 7 7. Leaf edge serrated ROWAN Leaf edge plain ASH 15 November 2018 G Davidson

Keys The paired statement key is more manageable as it tends not to spread itself out as much. The branching key is more pictorial and usually easier to use. Try building your own keys for the following organisms. (Branching and Paired Statement!) 15 November 2018 G Davidson

Tulip Cockle Sycamore Dandelion Giraffe Gold finch Mackerel Seaweed Spider Sea Urchin Venus Fly Trap Cockatoo 15 November 2018 G Davidson