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Explain the biotic factors affecting distribution of organisms

      

Explain the biotic factors affecting distribution of organisms

  

Answers

Masinde
Biotic factors can include parasites, predators, disease vectors, competitors, even food sources.Biotic interactions affect species' distribution through several mechanisms, such as predation, competition, resource-consumer interactions, host-parasite interactions, mutualism and facilitation.

.Biotic interactions within the same trophic level
Competition between animals can affect range limits and geographic diversity patterns. The competitive interactions may affect geographic ranges as illustrated by displacements of native species by other closely related introduced species.For example, the displacement of European red squirrel Sciurus vulgaris by the introduced S. carolinensis across much of the British Isles.Another case is the expansion of leopards during the early Middle Pleistocene probably replaced pumas in their Old World area of origin.

Plants competition and facilitation also affect species' geographic ranges over broad geographic extents.For example, light-demanding pioneer shrub and dwarf-shrub species were first replaced by light-demanding and taller pioneer trees and then by shade-tolerant late-successional tree species.

.Biotic interactions across trophic levels
Predator-prey.The presence of predators, can strongly influence the abundance, distribution and range limits of prey species in terrestrial, fresh water and marine systems.For instance,wolf predation limiting the recruitment of moose and survival of adult moose.Conversily, the eradication of wolves results in a strong increase in moose density, with consequent overbrowsing of riparian vegetation and the disappearance of migratory birds in the impacted willow communitie.

Animals and food plants.The dependence of animals on plants largely determines species distributions at broad spatial extent.For instance, the expansion of a polyphagous butterfly in Britain is associated with the exploitation of more widespread host plants.

Interactions and feedbacks between plants and soil biota

The interactions between plants and their associated soil biota can also play a significant role in determining the plant range expansion. Plant species which are undergoing active range expansion, for example as a result of climate change, show different interactions with their below-ground biota than related species that do not.For instance,non-expanders are in most cases negatively influenced by soil biota , whereas the range expanders are weakly negatively affected.

Host-parasite and host-pathogen.The presence and distribution of parasites and pathogens largely impact on the distribution patterns of organisms from regional to global extents.For example, the decline and partial extinction of the native noble crayfish Astacus astacus in many European lakes was driven by the fungal pathogen (Aphanomyces astaci) introduced to Europe.For parasites, the population decline of grey partridges Perdix in the UK was as a result of parasite-mediated competition with the ring-necked pheasant Phasianus colchicus.
Mr Masinde answered the question on April 27, 2018 at 09:01

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