The Biosphere Investigating an Ecosystem G Davidson Mr

The Biosphere Investigating an Ecosystem G Davidson Mr G Davidson

Investigating an Ecosystem • Examples of ecosystems include a woodland, pond, loch, moor etc. . • An ecosystem includes all the living things, their non-living surroundings and the factors which affect their lives. • Factors in the ecosystem related to living things are called Biotic Factors. 2/15/2022 G Davidson 2

Investigating an Ecosystem • Examples of these are the amount of food, disease, the amount of grazing and hunting. • Non-living factors in the ecosystem are called Abiotic factors. • Examples of these are temperature, moisture and light. 2/15/2022 G Davidson 3

Investigating an Ecosystem • The place where an organism lives is called a habitat. • There are many habitats within an ecosystem. • E. g. in a woodland there are many layers and within these layers many different habitats such as trees, leaves (dead and alive), shrubs, bushes, soil, etc. . 2/15/2022 G Davidson 4

Using a Quadrat • We could find out exactly what is living in a particular ecosystem by collecting and counting all the organisms. • This would be difficult and would take a long time. • However, we can get some idea of the amount and kinds of living things in an ecosystem by taking a sample. 2/15/2022 G Davidson 5

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. 2/15/2022 G Davidson 6

Using a Quadrat • The quadrats we use are 0. 25 m 2 and sub -divided into 25 smaller squares each 100 cm 2. • 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. 2/15/2022 G Davidson 7

Other sampling Techniques • Pitfall traps are used to trap small animals moving across the surface of the ground. • Sweep netting is used to catch small animals living in vegetation. • Potato traps can be used to attract small animals, particularly snails and slugs. 2/15/2022 G Davidson 8

Pitfall Trap 2/15/2022 G Davidson 9

Other sampling Techniques • Pond nets are used to catch animals living in ponds. • Tullgren funnels are used to remove tiny organisms from soil samples. • Pooters are used to capture small insects. 2/15/2022 G Davidson 10

Pond Net 2/15/2022 G Davidson 11

Tullgren Funnel 2/15/2022 G Davidson 12

Pooter 2/15/2022 G Davidson 13

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. 2/15/2022 G Davidson 14

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. 2/15/2022 G Davidson 15

Estimating Total Numbers • Calculate the area of this field. • Length times breadth. 15 m 40 m 2/15/2022 G Davidson 16

Estimating Total Numbers • We now know the area of the field is: 15 x 40 = 600 m 2. • 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. 2/15/2022 G Davidson 17

Sampling Daisies The quadrats are placed randomly and the number of daisies in each are counted. 15 m 40 m 2/15/2022 G Davidson 18

Sampling Daisies Quadrat Number of daisies 1 7 2 15 3 9 4 2 5 12 6 0 7 13 8 6 9 10 10 16 2/15/2022 • 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. G Davidson 19

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. 2/15/2022 G Davidson 20

Sampling Daisies • The field is 600 m 2 and there are 4 quadrats to each 1 m 2. • 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. 2/15/2022 G Davidson 21

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. 2/15/2022 G Davidson Quadrat No. of Worms 1 6 2 7 3 2 4 9 5 12 6 5 7 7 8 6 9 8 10 8 22

Estimating Total Numbers 25 m 40 m 25 m 50 m 2/15/2022 G Davidson 23

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) = 1625 m 2 Total number of quadrats in field? Answer - 1625 x 4 = 6500 quadrats Total number of worms? Answer – 6500 x 7 = 45 500 worms 2/15/2022 G Davidson 24

Factors Affecting Distribution • There are many different factors in an ecosystem which affect the lives of organisms. • The factors are also responsible for the distribution of the organisms, i. e. where they live. • Some of these factors – the abiotic factors – are easy to measure, e. g. light, moisture, temperature. 2/15/2022 G Davidson 25

Measuring Abiotic Factors • 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. 2/15/2022 G Davidson 26

Measuring Abiotic Factors • We can measure moisture using a moisture meter. • Carefully push the probe vertically into the soil to a depth of approximately 4 cm. 2/15/2022 G Davidson 27

Measuring Abiotic Factors • When we measure abiotic factors, we wouldn’t simply take one measurement and assume that was it. • We would take a number of measurements at different spots, and then calculate an average. • This makes our results more VALID. 2/15/2022 G Davidson 28

Line Transect 1 2 2/15/2022 3 4 5 6 Sample sites G Davidson 7 8 9 10 29

Line Transect • In this example the light intensity would decrease as you move from site 1 to 10. • The moisture readings would increase as you move from site 1 to 10. • Therefore, the distribution of plants are different – i. e. there are likely to be more daisies at site 1 than site 10. • Likewise there are likely to be more woodlice at site 10 than at site 1. 2/15/2022 G Davidson 30

Scientist studying Distribution of Organsims 2/15/2022 G Davidson 31

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. 2/15/2022 G Davidson 32

Branching Keys Start Legs No Leks 6 legs BEETLE 2/15/2022 ANT No shell Shell More than 6 legs 8 legs More than 8 legs MITE MILLIPEDE G Davidson SNAIL Segmented body Body not segmented EARTHWORM SLUG 33

Branching Keys • When using a branching key you must always start at the top. • If you follow the line of the key, you will be given a choice to make. • Study your organism and make the appropriate choice. • If your organism is in the key, you should eventually finish at its name. 2/15/2022 G Davidson 34

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. 2/15/2022 G Davidson 35

Paired Statement Key 1. Single leaf go to 2 2. go to 6 Several leaflets 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 2/15/2022 ASH G Davidson 36

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!) 2/15/2022 G Davidson 37

Tulip Giraffe Spider 2/15/2022 Cockle Gold finch Sea Urchin Sycamore Mackerel Venus Fly Trap G Davidson Dandelion Seaweed Cockatoo 38