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Week 7

Week 7. Tuesday: Complete G1 Guided notes worksheets Wednesday – Data Collection outdoors! Friday – COMPUTER LAB IN MONTICELLO – EXCEL AND DATA ANALYSIS. COMPLETING G1. COMPETITION NICHE CONCEPT COMPETITIVE EXCLUSION NICHE PARTITIONING. What is ‘competition’ in Ecology?.

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Week 7

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  1. Week 7 • Tuesday: Complete G1 Guided notes worksheets • Wednesday – Data Collection outdoors! • Friday – COMPUTER LAB IN MONTICELLO – EXCEL AND DATA ANALYSIS

  2. COMPLETING G1 • COMPETITION • NICHE CONCEPT • COMPETITIVE EXCLUSION • NICHE PARTITIONING

  3. What is ‘competition’ in Ecology? Competition occurs when individuals use a shared resource in short supply: There may not be enough of the resource for any given individual to survive, or to reproduce, as well as when more resource is present. Competition does not necessarily involve competitors ever meeting (if the competitors are mobile organisms, such as many animals), or being adjacent to each other (if sessile organisms, such as plants or fungi).

  4. As a result of competition: • Birth rates are lower, death rates higher, or both. • In ecological terms, population growth rates decrease and population size is lower at equilibrium • In evolutionary terms, an individual's fitness is lower. • Competition is a density dependent effect on population dynamics

  5. Competition can be intraspecific or interspecific Interspecific Competition Competition between different species which depend on the same resource: • Food • Water • Nesting Sites • Breeding Sites

  6. Intra-specific competition • Example: Adaptive Radiation in Darwin’s Finches • Example: Competition for mates

  7. LET’S REVIEW OUR INTER-SPECIFIC RELATIONSHIPS • PBS marine interactions • Marine Mutualism

  8. The Niche Concept: Definition • ‘Nicher’ – to Nest: • A term describing the way of life of a species: The specialised habitat of an organism: • space and territory • Nutrition and feeding habits • Interactions with other organisms • Its reproductive habits • Its role in the community

  9. The Niche concept: A Working Analogy In 1927, Charles Sutherland Elton, the British Ecologist, stated: ‘When an ecologist states ‘There goes a badger’, he should include in his thoughts a definite idea of the animal’s role in the community, just as if he had said ‘There goes the vicar’

  10. Niche Concept: The Boundary conditions Two species that use exactly the same resources cannot occupy the same niche Only one species or population can occupy the same niche for an extended period

  11. Fundamental and Realised Niches Fundamental Niche A species’ fundamental niche is the full range of environmental and social conditions under which it could potentially survive and reproduce

  12. Realised Niche The realised niche is the specific set of conditions in which it survives in a given habitat or ecosystem, given the other species or limitations present. These are the conditions to which the species is best adapted.

  13. The Competitive Exclusion Principle Aka ‘Gause’s Law’ ‘No two species can occupy the same niche for a prolonged time’

  14. The Competitive Exclusion Principle • If two species share a niche, there must be inter-specific competition for resources • The best adapted species will survive • The loser will struggle to survive and reproduce, and will eventually become extinct OR migrate (if its niche is broad enough) Examples are abundant • Invasive species • Red versus Grey Squirrel in Western Europe • Gause’s Paramecium

  15. Competitive Exclusion: Squirrels

  16. Competitive Exclusion: Squirrel Distribution

  17. The Classic Example of Competitive Exclusion: Paramecium GeorgyGause cultured 2 species of the protist Paramecium: • P. Aurelia • P. Caudatum • Grown together under ideal conditions, both populations reach a higher maximum • Grown together, one species rapidly becomes extinct…

  18. Does Competitive Exclusion work in the real world?.... The competitive Exclusion principle is actually rarely observed in natural ecosystems: • ‘spatial heterogenity’ (niche partitioning) • Niche sharing associated with availability of multiple resources • ‘The paradox of the plankton’: Why do so many plankton species exist in a small, limited, homogenous habitat?

  19. Niche Partitioning 1. Spatial: Two different species use the same resource by occupying different areas within the range of the resource 2. Temporal: Two species eliminate direct competition by using the same resource at different times 3. Morphological: Two different species evolve different morphologies in order to use a resource in different ways

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