Habitat & Niche
1
Habitats and Niches
March 21, 2016
Habitat
2
 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.


physical and biotic
environment
vegetation

Forest, meadow, pasture,
coniferous forest, etc.
Habitats and Niches
March 21, 2016
Habitat
3
 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
March 21, 2016
What is the niche?
4
 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
March 21, 2016
Niche types
(a) Fundamental niche:
5
All resources that could be used in absence of competition.
 depends on physical (abiotic) conditions.

Habitats and Niches
March 21, 2016
Niche types
6
(b) Realized niche:
Resources actually used
in presence of
competitor.
 depends on biotic as
well as abiotic
conditions.

Habitats and Niches
March 21, 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
8
Habitats and Niches
March 21, 2016
Resource partitioning
9
 Resource partitioning
avoids competition;
 Realized niches divide
resources among several
species.
Habitats and Niches
March 21, 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.

Human history littered with examples of introducing exotic
species to solve problems caused by previous introductions.

Mongoose and Rats in Caribbean
Invasive species
13
 Invasive species
competitively exclude
native species:

Imported fire ant

Kudzu

Purple loosestrife

Zebra mussel
Habitats and Niches
March 21, 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.


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.


Sharp boundaries - Closed communities
Indistinct boundaries - Open communities