Transcript Habitat & Niches

Habitat & Niche
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Habitats and Niches
April 12, 2016
Habitat
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 place where an animal or
plant lives
 where it gets food
 where it gets water
 type of environment in
which a population or
species regularly lives.
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physical and biotic
environment
vegetation
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Forest, meadow, pasture,
coniferous forest, etc.
Habitats and Niches
April 12, 2016
Habitat
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 Habitats may be subdivided into layers or zones
 Microhabitats
Forest canopy: leaves, branches
 Shrub layer: leaves, branches, trunks
 Herb layer:
leaves, stems, mosses, ferns
 Litter:
dead fallen leaves, logs,
 Varies in depth, quality
 Soil: topsoil, subsoil

Habitats and Niches
April 12, 2016
What is the niche?
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 set of conditions within
which an organism can
maintain a viable population
ecological
 total set of environmental
light intensity
niche
factors that determines a
species’ distribution.
okay
 An organism’s role within a
temperature
salinity
community.
Habitats and Niches
April 12, 2016
Niche types
(a) Fundamental niche:
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All resources that could be used in absence of competition.
 depends on physical (abiotic) conditions.
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Habitats and Niches
April 12, 2016
Niche types
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(b) Realized niche:
Resources actually used
in presence of
competitor.
 depends on biotic as
well as abiotic
conditions.
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Habitats and Niches
April 12, 2016
Law of Competitive Exclusion
 No two species will occupy the same niche and
compete for exactly the same resources for an
extended period of time.
 When forced to compete, one will either migrate,
become extinct, or partition the resource and utilize
a sub-set of the same resource.
 Given resource can only be partitioned a finite
number of times.
Law of Competitive Exclusion
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Habitats and Niches
April 12, 2016
Resource partitioning
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 Resource partitioning
avoids competition;
 Realized niches divide
resources among several
species.
Habitats and Niches
April 12, 2016
Resource Partitioning
Keystone Species
 A species or group of species whose impact on its
community or ecosystem is much larger and more
influential than would be expected from mere
abundance.
 Large predators
 Critical food organisms (bamboo and pandas)
 Often, many species are intricately interconnected
so that it is difficult to tell which is the essential
component.
Introduced Species
 If introduced species prey upon or compete more
successfully than native populations, the nature of
the community may be altered.
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Human history littered with examples of introducing exotic
species to solve problems caused by previous introductions.
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Mongoose and Rats in Caribbean
Invasive species
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 Invasive species
competitively exclude
native species:
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Imported fire ant
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Kudzu
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Purple loosestrife
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Zebra mussel
Habitats and Niches
April 12, 2016
Kudzu – Invasive & Exotic
Abundance and Diversity
 Abundance -Total number of organisms in a
community.
 Diversity - Number of different species, ecological
niches, or genetic variation.
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Abundance of a particular species often inversely related to
community diversity.
As general rule, diversity decreases and abundance within
species increases when moving from the equator to the poles.
Edges and Boundaries
 Edge Effects - Important aspect of community
structure is the boundary between one habitat and
others.
 Ecotones - Boundaries between adjacent
communities.
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Sharp boundaries - Closed communities
Indistinct boundaries - Open communities