COMPARATIVE INVESTIGATION LAB ON LICHENS

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                Amrita Raichura

                11T

                Biology: Lab Report

COMPARATIVE  INVESTIGATION  LAB  ON  LICHENS

Design

Research Question:

Is there a significant difference calculated by the t-test to show that the percentage coverage of lichens found on the north side of the trees after one meter from the base of the tree be affected by the tree being either in the shaded or the sunny area?

Variables:

Dependent variable: - the number of lichens found on the trees.

Independent variable: - trees found in the shaded areas and trees found in the sunny areas.

Constant variable: -  lichens found on the North side of the tress

      -  lichens found after one meter from the base of every tree

      -  the altitude at which the trees are looked at

-  the same soil type for all the trees

-  the surface of the trees not being too rough and very similar

      -  the humidity of the area from where the trees are looked at

- almost the same amount of sunlight reaching the trees in the sunny     area

- almost the same amount of sunlight reaching the trees in the shaded     area

-  the amount of water available to the trees

Hypothesis:

Lichens produce their food from the sunlight with the help of its photosynthetic partner. It is more likely for lichens to grow on trees in large number in an area that has more sunlight compared to an area that is shaded. Therefore, the percentage coverage of lichen on the trees is going to be higher in an area with sunlight compared to a shaded area. Also the direction of the tree (North, East, West or South) affects in the growth of lichen.

Apparatus:

  • Meter rule (x1)
  • Compass (to find the north direction) (x1)
  • Mini transparent quadrat with marked squares (x1)
  • Pencil / pen
  • Paper
  • Calculator

Method for controlling variables:

  • The investigation should take place in two different areas, one which has trees growing in a sunny area and another one which has trees growing in shaded area and it should not be carried out elsewhere from these two selected area.
  • Use a compass to exactly know where the North side of the tree is so that percentage coverage could be found out in that area.
  • Look at and cover each of the selected area as much as possible by looking at many trees all over the shaded or the sunny area.
  • Use a meter rule to mark the point after exact one meter from the bottom of the bark of the tree so that the area being looked at remains the same for all the trees.
  • Check the soil type on which the trees are growing, make sure that the amount of moist felt by touching it is very similar in for all the trees.
  • The trees that are being investigated should be found on a flat land so that the altitude of the area remains the same and also the amount of humidity would be similar.

Method for collecting data:

  1. Look for trees with lichen on its bark in shaded areas, where a lot of sunlight is not obtained and look for trees with lichen on its bark in sunny areas where sunlight is obtained almost through out the day.
  2. For each tree, using a compass find the North side of the tree.
  3. On the North side of the tree, take a 1 meter measuring rule and put it at the bottom of the bark so that the area after one meter on the North side of the tree is found.
  4. Allocate the mini transparent quadrat on the area found with lichens (North side of the tree after one meter from the bottom of the bark).
  5. Count the number of squares that are covered by lichens. If the squares are half full, count it one by adding another square that is half full. If only the quarter of the square is full, make it one by putting together four, quarter full squares together. If any squares are less then a quarter covered by lichen, do not include it in the data collection.
  6. The total number of squares covered by lichen will be the percentage coverage (as there are 100 squares in total within the quadrat) of lichen on the selected area of the tree.
  7. Collect the percentage coverage of lichens from 20 trees in found shaded area and 20 trees found from the sunny area.
  8. Repeat the same steps from number 2 till number 6 for each tree being investigated for lichen coverage and record your data.
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Diagram for data collection:

This is a small illustration showing how the investigation should be done and how it should look like.


Data Collection and Processing

Data collection table:

Data processing:

Average percentage coverage of lichen on trees found in sunny area:

Average   =   ...

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