Wednesday, December 12, 2012

Dimorphism - Functional Anomaly in Nature

Dimorphism is exhibited by plants in having two distinct forms of any part, such as the leaves and flowers. In animals dimorphism occurs as two distinct types of individuals in a species

Dr Abe V Rotor

Starfish normally has five arms. Variants may have four or six arms.

In Chemistry, it is a property of certain substances that enables them to exist in two distinct crystalline forms (dimorphic, dimorphous adj). Polymorphic refers to more than two distinct forms. It is found mostly among lower organisms. Sargassum the dominant brown seaweed in the tropics is polymorphic. Variants sometimes lead to erroneous taxonomic classification.

Dimorphic or polymorphic characteristics may be functional such as in the Drynaria fern. The long and serrated leaves are mainly for photosynthesis, while the cup-like leaves protects the rhizomes, and gathers and stores humus and water.

Dimorphism and polymorphism are indications that evolution is taking place in nature. The variant forms are either remnants or advanced forms that accompany evolution. Scientists associate this phenomenon with mutation which accompanies speciation, the formation of new species.

Mickey Mouse plant has two distinct flowers borne on the
same plant. Yellow flower is the male, red is the female.Staghorn fern has two types of leaves: dangling staghorn shape,
and upright funnel-like leaves, Drynaria fern is also dimorphic. 

Cup-shape leaves of Drynaria fern supplements photosynthesis when young, then dry up to form a shed of shingles to gather humus and water, and cover the delicate rhizome. These secondary leaves protect the aestivating fern in summer.

Colored young leaves will turn normal green upon maturity,
thus this ornamental plant is not dimorphic.
Talisay leaves turned prematurely yellow ahead of the
deciduous timetable of the plant - not an example of
dimorphism from the typical talisay (Terminalia catappa)

Dual colored orchid is a result of crossing of parents having
yellow and red flowers - not an example of dimorphism.

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