Effect Of Abiotic Factors On Distribution Of Detritivores Biology Essay

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Detritovores are found both in leaf litter and top soil layers. They are primarily decomposers and are very important in the efficient and healthy processing of dead organic matter. Detritovores are very sensitive to changes in many abiotic factors, and this can have a profound influence on their distribution and population size.

Independent variables (changed):

- Weight of the two soils

Dependent variables (measured):

- pH of both soil types

- Temperature of both soil types

- Soil moisture content of both soil types

In order to effectively control the variables above, it is important to follow the instructions below:

- The pH values of the two soil samples have to be measured carefully with the data logger (see 'Methods of data collection' section below)

- The temperatures of the two soil samples have to be measured carefully, again using the data logger (see 'Methods of data collection' section below)

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- The steps for achieving accurate moisture content results have to be completed correctly (see 'Methods of data collection' section below)

Methods of data collection:

pH:

In order to get pH results for the two soil samples the data logger was used. The results were automatically converted to the pc.

Moisture:

Both, soil A and soil B were weighted (both had to be the same weight). Then, the two samples were heated in an oven for hours. Afterwards, this weight was noted and the difference to the beginning was calculated (which then indicated the moisture content).

Temperature:

For temperature measurements, the data logger was used. The measurements were sent to the pc.

Results:

Table 1 showing moisture content of different soil samples:

Weight before heating

(in grams)

Weight after heating

(in grams)

Moisture Content

(in grams)

Sample A (soil under tree)

1080

996

84

Sample B (sand)

1080

1066

14

Graph 1

Table 2 showing temperatures for soil sample A:

Sample A

 

Channel1

 

Time

e.Log-Temperature

 

s

°C

 

0

0

18.1

1

10

17.9

2

20

17.8

3

30

17.8

4

40

17.8

5

50

17.7

6

60

17.7

7

70

17.7

8

80

17.7

9

90

17.7

10

100

17.7

11

110

17.7

12

120

17.7

13

130

17.7

14

140

17.7

15

150

17.6

16

160

17.7

17

170

17.7

18

180

17.7

Average

17.7

Table 3 showing temperatures for soil sample B:

Sample B

 

Channel1

 

Time

e.Log-Temperature

 

s

°C

 

0

0

20.1

1

10

19.9

2

20

19.9

3

30

19.8

4

40

19.8

5

50

19.8

6

60

19.7

7

70

19.8

8

80

19.7

9

90

19.7

10

100

19.7

11

110

19.7

12

120

19.7

13

130

19.7

14

140

19.7

15

150

19.7

16

160

19.7

17

170

19.7

18

180

19.6

Average

19.8

Graph 2

Table 4 showing pH values for different soil samples:

Sample A

pH 7.5 (Alkaline)

Sample B

pH 7.5 (Alkaline)

Table 5 showing number of organisms found in soil sample A and B:

Sample Number (1 ml each)

#1

#2

#3

#4

#5

#6

#7

#8

#9

#10

Total

Soil sample A

7

15

6

13

14

19

18

8

5

15

120

Soil sample B

0

0

0

0

0

0

0

0

0

0

0

Discussion, evaluation and conclusion:

As table 1 and graph 1 indicate, there are differences in soil moisture between soil sample A and soil sample B. After heating both, the soil from under the tree and the desert sand, and calculating the difference in weight, it has become clear that soil A has a higher moisture content (84 grams) than soil B (14 grams). This is due to the fact that soil B is exposed to sunlight during the whole day, because there are no trees or bushes. Hence, water evaporates quite easily and fast, leaving the soil very dry. Soil A however, was collected directly under a tree. Firstly, trees give shadow and therefore this soil is less affected by sunshine than soil B, reducing the evaporation rate. Secondly, due to this reduced evaporation rate, more water is present in the soil, making it humid. Hence, moisture content is much higher. The effect of soil moisture content on population size of different soils can be shown be these results. Table 5 shows the number of organisms found in sample A and B. As one can see, in ten 1 ml samples (these samples were taken from a 150 ml beaker) 120 organisms were found in soil A, whereas in soil B, not a single organism was found. This suggests that specific animals prefer living in humid and wet areas, rather than dry regions, because living conditions are much more preferable.

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Besides moisture content, different temperatures were observed. As table 2 and 3, as well as graph 2 show, temperatures for soil B were much higher than for soil A. Graph 2 illustrates a slight decrease in temperature for both soil samples. This is because the two samples cooled down when they were collected and taken inside the laboratory (no direct sunlight present). The average temperature for soil sample A was 17.7 °C, whereas the average temperature for soil B was 19.8 °C. This result is due to the fact, that soil B, the sand, was, as already mentioned, located in the middle of the desert, without any trees or bushes. Soil A, in contrast, was covered by a tree. Hence, sunlight warmed up soil B more intensely than soil A. As table 5 indicates, way more organisms were found in soil sample A (none found in sample B). This shows that organisms prefer living in cooler areas, also, as already discussed before, because cooler regions are more humid than hotter areas.

Lastly, soil pH was measured. As table 4 indicates, there weren't any differences between the two samples, but both measured 7.5 on the pH scale, which is slightly alkaline. This indicates, that soil pH has a smaller effect on the distribution of organisms than temperature or moisture. The results also suggest, that, because the two samples are near of being neutral, the areas observed are not affected by human influences such as fertilizers or the use of chemicals (which would alter pH values to a great extent).

Nevertheless, there are some improvements which can be made in order to obtain more accurate results when counting the number of organisms present in both soil samples. Firstly, only ten 1 ml samples were taken from the 150 ml beaker. To improve these results, it is probably better to uses more samples (the more the better). Also, instead of using only 1 ml samples, 2 or 3 ml samples could be used. Moreover, when counting the number of organisms, it is likely that some were missed out or counted twice. It is important to count very carefully and not miss out even very small organisms.

In conclusion, as the results have shown, more organisms were present in soil sample A. This is because soil A had a higher moisture content than soil B, as well as lower temperatures.