1. Habitat & Niche
Habitats and Niches
June 4, 2018

2. Habitat 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
June 4, 2018

3. Habitat 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
June 4, 2018

4. What is the niche?
set of conditions within which an organism can maintain a viable population
total set of environmental factors that determines a species’ distribution.
An organism’s role within a community.
temperature
light intensity
okay
salinity
ecological
niche
Habitats and Niches
June 4, 2018

5. Niche types (a) Fundamental niche:
All resources that could be used in absence of competition.
depends on physical (abiotic) conditions.
Habitats and Niches
June 4, 2018

6. Niche types (b) Realized niche:
Resources actually used in presence of competitor.
depends on biotic as well as abiotic conditions.
Habitats and Niches
June 4, 2018

7. 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.

8. Law of Competitive Exclusion
Habitats and Niches
June 4, 2018

9. Resource partitioning
Resource partitioning avoids competition;
Realized niches divide resources among several species.
Habitats and Niches
June 4, 2018

10. Resource Partitioning

11. 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.

12. 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

13. Invasive species
Invasive species competitively exclude native species:
Imported fire ant
Kudzu
Purple loosestrife
Zebra mussel
Habitats and Niches
June 4, 2018

14. Kudzu – Invasive & Exotic

15. 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.

16. 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