Name of TeacherDr Brijesh Pathak Designation Assistant Professor
Name of Teacher-Dr. Brijesh Pathak Designation- Assistant Professor Address-University College, Dhilwan, Tapa Subject Name- Botany (Ecological Succession) B. Sc. (Medical)-Semester VI
Ecological Succession • Defined as gradual replacement of one community by the other • An orderly process of community change in a unit area (E. P. Odum) Types of Ecological Succession: - • Primary and Secondary (based on starting) • Autogenic and Allogenic (based on cause) • Autotrophic and Heterotrophic (based on community) • Hydrosere and Xerosere (based on substratum)
Primary Succession: - • Starts from area where there was no previous living matter • Areas include rock surface and newly created pond • Examples include lichen and Phytoplankton Secondary Succession: - • Starts from previously built-up substratum (already existing living matter) • Sudden changes causes disappearance of existing community • Examples include fire and snow fall
Autogenic Succession: - • After succession has begun, the community itself modify its own environment and thus causing its own replacement Allogenic Succession: - • Replacement of existing community by externalconditions and not by the existing organisms Process of Succession: 1. Nudation 2. Invasion 3. Competition and coaction 4. Reaction 5. Stabilisation
Nudation: • Pioneer community • Development of bare area • Causes of nudation include Topographic, Climate and Biotic factors Invasion: - • Successful establishment of a species in a bare area • Migration, Ecesis and Aggregation are components of invasion • Migration include dispersal, Ecesis means successful establishment of species and Aggregation means staying close to each other
Competition and Coaction: • Aggregation results in increase in species number which causes competition (intra-specific and interspecific) • Individuals of species affect each other called coaction • Both these factors results in elimination of unfit individuals and survival of fit individuals Reaction: - • It is modification of environment through the influence of living organism present in it Stabilisation: • Climax community which maintain equilibrium with climate of the area
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