Page 78 - Biology - XII

Symbiotic Association,
Symbiotic Association,
Homologous and Analogous
7 Homologous and Analogous
Organs
Organs

EXPERIMENT - 14

Objective
To study symbiotic association in root nodules of leguminous plant, Cuscuta on host and a lichen through
model/specimen/charts.

Principle/Theory
In nature animals, plants, and microbes interact with each other in various ways.
1. When two diff erent species interact and are in close association, one species is benefi ted while the
other species may have positive, negative, or neutral impact. Such association is called a symbiotic
relationship.
2. There are three basic types of symbiotic relationships:
• Mutualism (Both species are benefi ted.)

• Commensalism (One species is benefi ted while the other is neither benefi ted nor harmed.)
• Parasitism (One species is benefi ted and the other is harmed.)

Materials Required
Model/specimen/chart showing symbiotic association in root nodules of leguminous plant (pea plant),
Cuscuta on host and a lichen

Procedure
1. Observe the specimens.
2. Compare the comments mentioned.

Comments
1. Rhizobium is in root nodules of leguminous plant (pea plant)
(i) Rhizobium bacteria are present in root nodules
of leguminous plant and form a symbiotic
relationship, mutualism, where both the species
are benefi ted from each other. Nitrogen fi xing
bacteria like Rhizobium fi xes atmospheric Leguminous plant Rhizobium
nitrogen into nitrogenous compounds.
(ii) Rhizobium can convert atmospheric nitrogen
to ammonia that can be used by pea plant for Root nodule
growth and development.
(iii) Bacteria receive nutrients and suitable place to
grow from the pea plant.
Fig. 14.1: Legume plant's root showing nodules

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