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Exercise 24: Procedure

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13 views2 pages

Exercise 24: Procedure

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dillibabu
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Exercise 24









 

 



Procedure
(i) In the selected site of study, make a 1 m X 1 m quadrat with the help of
nails and thread. Hammer the nails firmly and make sure that the
vegetation is not damaged while laying the quadrat.
(ii) List the names of the plant species seen in the quadrat (if the name is not
known mark these as species A or B etc. and if the same species is seen in
other quadrats assign the same alphabet)
(iii) Similarly lay nine more quadrats randomly in the site of study and record
the names of individuals of each species.
(iv) Calculate the percentage frequency of occurrence using the formula given.

Observations
Record the total number of species seen in the ten quadrats. This will give an
idea about the composition of the vegetation.
There will be difference in the species composition in the quadrats made in
shady areas, exposed areas with bright sunlight, dry or wet areas etc.
Observe that the frequency of occurrence is not the same for all species.

21/04/2018
LABORATORY MANUAL: BIOLOGY

Table 24.1: Frequency studies for the given vegetation

Plant Number of quadrats employed No. of quadrats Percentage


Species in the study (Q) in which the of frequency
species is present (N) F=N/Q X 100
I II III IV V VI VII VIII IX X

A √ √ √ √ √ 5 5/10 × 100 = 50%

B √ 1 1/10 × 100 = 10%

C √ √ √ √ 4 4/10 × 100 = 40%

Discussion
Variation in distribution of a species is caused by factors like soil conditions,
quantity and dispersal of gemmules, vegetative propagation, grazing, predation,
diseases and other biotic activities. Also frequency values differ in different
communities. They are influenced by micro-habitat conditions, topography,
soil and many other environmental characteristics. Thus unless frequency is
not correlated with other characters such as density, frequency alone does not
give correct idea of the distribution of a species.
Frequency determinations by means of sample areas are often needed in
order to check general impressions about the relative values of species. Many
species having low cover or population density also rate low in frequency, but
some may have high frequency because of their uniform distribution. Usually
if the cover and population density are high, the frequency will be high. The
plants with high frequency are wide in distribution.

Questions
1. If frequency of a plant is high, what will be your interpretation?
2. Can many micro-habitat in an area affect frequency of a species? Comment.

88

21/04/2018

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