Decomposers and Detritus Feeders
Observe the following organisms under the microscope.
1. Bacteria
a. Bacteria – three types
b. Note and draw the three different shapes.
i. Bacillus – rod.
ii. Coccus – sphere
iii. Spirillum – coil
c. How do bacteria contribute to the nitrogen cycle?
2. Fungi
a. Rhizopus – mold
i. The hair-like filaments are called hyphae. This is the body of the fungus. Hyphae
secrete enzymes that digest detritus.
ii. The spherical structures are sporangia. Sporangia are spore forming products of
sexual reproduction.
b. Coprinus – mushroom cross section
i. Mushrooms are the product of sexual reproduction. The body of the fungus would
be under the ground and made of hyphae.
ii. Note the flat “gills” that radiate from the central stem. The “gills” produce spores.
c. Fungi can digest cellulose how is this important to soil formation?
3. Animal Kingdom
a. Rotifer
i. Note the corona; a crown of hair-like structures call cilia. Rotifers use this
structure to collect food.
ii. Note the tapered end. Rotifers can attach themselves to a substrate using a sticky
substance secreted by glands or they can move along like an inchworm.
b. Earthworm
i. Observe the earthworm using a dissecting scope.
ii. Identify the mouth and anus and note the segmented body.
iii. Note the short hair-like structures found in each segment. These are setae. What is
the purpose of setae?
iv. Note the smooth section of the body. This is the clitellum. The clitellum secretes a
cocoon after mating and fertilized eggs are deposited into it.
v. Locate the openings in segment 14 – these are the female genital openings. Locate
the openings in segments 9 and 10 – these are the seminal receptacles. What is the
function of these parts?
Microscopic observation of humus samples
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Fill a 50mL beaker half way with fine humus.
Add enough distilled water to saturate the humus.
Stir with a plastic dropper then place a drop of suspended humus onto a depression slide.
Cover the drop with a cover slip.
Scan the specimen. Repeat if necessary.
Classify any organism you see as Bacteria, Fungi or Animal.