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(1) Community [ Ecology ]

Dictionary of botanic terminology - index of names

     
  In ecology a community is a characteristic assemblage of populations of plants, animals and other organisms that live in a specific area (habitat), within relatively similar environmental conditions and have mutual relationships among themselves and to their environment, and thus functioning, at least to some degree, as an ecological unit.  
     
All organisms living in a particular ecosystem constitute a community, while the group of organisms of a single species in an ecosystem is called population. For example, a pond may contain insects, frogs, fish and plants, together forming a biotic community, but it is made up of different populations (e.g. frog population, insect population, fish population, etc).

Communities are often defined by the most abundant or obvious organisms or dominant species (e.g. kelp forest community means all the animals and plants that are part of the kelp forest) or the major physical characteristics of the area (e.g. mudflat community).

Structure of community: community contains three fundamental groups producers, consumers and decomposers-which are dependent on each other and maintain a dynamic, stable community in spite of many deaths and new arrivals.

(2) Community   [ Ecology ]
     
  The region occupied by a group of interacting organisms.  
     

 


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Holdfast roots  [ Botany  ]

Dictionary of botanic terminology - index of names

 
     
  Some species of climbing plants develop holdfast roots which help to support the vines on trees, walls, and rocks. By forcing their way into minute pores and crevices, they hold the plant firmly in place.  
     
Climbing plants, like the poison ivy (Toxicodendron radicans), Boston ivy (Parthenocissus tricuspidata), and trumpet creeper (Campsis radicans),  develop holdfast roots which help to support the vines on trees, walls, and rocks. By forcing their way into minute pores and crevices, they hold the plant firmly in place. Usually the Holdfast roots die at the end of the first season, but in some species they are perennial. In the tropics some of the large climbing plants have hold-fast roots by which they attach themselves, and long, cord-like roots that extend downward through the air and may lengthen and branch for several years until they strike the soil and become absorbent roots.

Major references and further lectures:
1) E. N. Transeau “General Botany” Discovery Publishing House, 1994
   

 

 

 

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