(a) State what is an ecological succession.
(b) Write one similarity and one difference between hydrarch and
xerarch sucessions.
(c) Explain the mechanism of co-evolution as seen in orchid Ophrys and bee.
Answers
a) Ecological succession is the change in the structure of a biological community over a period of time. This time can vary from years to decades. There are two types of ecological succession:
1. Primary Succession: It occurs in areas which are basically lifeless such as bare rocks, glaciers and lava etc.
2. Secondary Succession: It occurs in area which already had an established ecosystem such as forest etc. which are destroyed by natural calamities like fire, hurricane and is changed to an ecology having lesser number of species.
b) Xerach Succession: This succession takes place in dry regions; phytoplanktons are replaced by free floating angiosperms which further invade grasses and trees.
Hydrach Succession: This succession takes place in wet areas, Lichens are the pioneer species, which are then invaded by bryophytes.
Similarities:
In both the successions a stable community is formed.
c) 1. Orchid Ophrys uses sexual deceit to attract the female bees.
2. In such case one of the petals of the flower resembles the female bee in size, color and markings.
3.The male bee gets attracted to it, as it resembles the female bee.
4. After which it pseudocoputes with the flower in turn of which the male bee dusts pollen on the flower.
5. When the male bee sits on another flower, to pseudocopulate , the male bee dusts the flower with pollen and pollinates it