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BY SURABHI TANWARMasters Student in the Environmental SciencesInstitute of Science, Mumbai
COMMUNITY ECOLOGY
What is a Community?
It is an assemblage of species living close enough together for potential interaction.
Communities differ in their species richness, thenumber of speciesthey contain, andthe relativeabundance ofdifferent species.
FOUR main kinds of species interactions; all play a role in the formation of community structure...
Competition (-,-)
Predation, parasitism (+,-)
Mutualism (+,+)
Commensalism (+,0)
Competition.◦Interspecies competition: can occur
when resources are limited.
Competition.
◦ Interspecies competition for resources can occur when resources are in short supply.
There is potential for competition between any two species that need the same limited resource.
◦ The competitive exclusion principle: two species with similar needs for same limiting resources cannot coexist in the same place.
G. F. Gause (1934) tested competitive exclusion principle
Ecological Niches
The total of a species’ use of biotic and abiotic resources is called the species’ ecological niche
Ecologically similar species can coexist in a community if there are one or more significant differences in their niches
As a result of competition, a species’ fundamental niche may differ from its realized niche
Fundamental Niche vs Realized Niche
Fundamental Niche: the niche that a species potentiallycould occupy, in the absence of competitors.
Realized Niche: the niche to which a species is restrictedin the presence of competitors.
Classic experiments confirm this.
Fig. 53.2
Resource Partitioning
Resource partitioning is differentiation of ecological niches, enabling similar species to coexist in a community
Character displacement
Body evolves as a result of resource partitioning.
Predation.
◦A predator eats prey.◦Herbivory, in which animals eat plants. ◦In parasitism, predators live on/in a host and
depend on the host for nutrition.
Offset oscillations in the population sizes of the predator and prey
Coevolution of predator and prey
◦Plant defenses against herbivores include chemical compounds that are toxic.
◦Animal defenses against predators. Behavioral defenses include fleeing, hiding, self-
defense, noises, and mobbing. Camouflage includes cryptic coloration,
deceptive markings.
Fig. 53.5Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Mechanical defenses include spines. Chemical defenses include odors and toxins Aposematic coloration is indicated by warning colors,
and is sometimes associated with other defenses (toxins).
Devil scorpionfish
backside
In Batesian mimicry, a palatable or harmless species mimics an unpalatable or harmful model
monarch viceroy
Cuckoo bee
Yellow jacket
In parasitism, one organism, the parasite, derives nourishment from another organism, its host, which is harmed in the process
Parasitism exerts substantial influence on populations and the structure of communities
Mutualism is where two species benefit from their interaction.
Coral polyp & zooxanthellae
Commensalism is where one speciesbenefits from the interaction, but other is not affected.
REFRENCES
http://www.bio.miami.edu/ecosummer/lectures/lec_coevolution.html
https://en.wikipedia.org/wiki/Ecological_niche
http://faculty.virginia.edu/bio202/lectures/LectureK7.pdf
http://ani_mardiastuti.staff.ipb.ac.id/files/2011/11/Biopop09_Resource-Partition.pdf
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