LABORATORY ACTIVITY
LABORATORY ACTIVTY NO.2
SURVEY OF FRESHWATER MICROORGANISMS
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Date:
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Algae are a diverse group of plant-like protists that inhabit various places like seawater, soil,
and freshwater environments like rivers, lakes and canals. They are found almost everywhere. They
play significant role in the ecosystem because they are the primary photosynthetic forms serving as food
source of zooplanktons and filter-feeders. In rivers and lakes, the phytoplanktons are dominated by the
cyanobacteria that can be abundant in naturally productive and eutrophied lakes.
The distribution of freshwater algae is affected by water strata. Bottom- dwelling or benthic
algae and rooted aquatic plants are found in the shallower areas whereas planktonic forms are found
floating on the water surface. Diatoms tend to dominate the lake sediments because of their resistant
siliceous cell.
At the end of the activity the students should be able to:
1. Familiarize themselves with the appearance and morphology of the different groups of freshwater algae.
2. Group the identified algae based on the existing taxonomic classification.
Materials
Bottles of pond water samples
Clean microscope slides and cover slips
Microscope
Pipette and forceps
Reference books
Procedure
1. Clean bottles thoroughly then collect pond
water along the vicinity of the campus.
2. Clean the slide and cover glass with soap and
water rinse thoroughly and dry. (Do not
attempt to study a slide that lacks a cover
glass).
3. When using a pipette, insert it into the
bottom of the bottle to get a maximum
number of organisms. Very few organisms will
be found swimming around in mid depth of
the bottle.
4. Use forceps to remove filamentous algae
from the bottle. Avoid putting too much
material on the slides.
5. Explore the slide first with the low power
objective and reduce the lighting with iris
diaphragm. Keep the condenser at its highest
point.
6. When you find an organism of interest, swing
the high-dry objective into position and
adjust the lighting to get the optimum
contrast.
7. Refer to figures 6.2 to 6.6 and reference
books to identify the various organisms that
you encounter.
Activities
1. Use the table below to record the genus and phylum of each identifiable type. Sketch on the
space provided the microorganisms that you were not able to identify.
GENUS
PHYLUM
2. Draw each organism that you see and identify them.
Answer the following questions
1. What is the most significant characteristic of each group of freshwater microorganisms?
2. In table form, compare each group of microorganisms below.
3. What difference do you observe between the water samples?
4. What is the implication of the findings you observe in these samples?
5. What is the economic importance of these groups of microorganisms?
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