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Ecological Niche and Community Dynamics: Understanding Organisms' Roles

Explore the distinctive lifestyles and roles of organisms in a community through the concept of ecological niche, considering both abiotic and biotic factors. Learn about fundamental and realized niches, limiting resources, and the impact of competition on niche occupation. Discover how mutualism, commensalism, and parasitism influence ecological interactions among species, and the significance of keynote and dominant species in community structure and functioning. Delve into concepts like species richness, diversity, and ecological succession, and the nature of communities as seen through the organismic and individualistic models.

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Ecological Niche and Community Dynamics: Understanding Organisms' Roles

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  1. Chapter 52 Community Ecology

  2. Ecological niche • Distinctive lifestyle and role of an organism in a community • Takes into account all abiotic and biotic aspects • For example, an organism’s habitat is one parameter used to describe the niche

  3. Connections to the size of the acorn crop

  4. Fundamental niche • Potential ecological niche for an organism • Realized niche • Niche an organism actually occupies • Limiting resources • Environmental factors that restrict a realized niche

  5. Effect of competition on an organism’s realized niche

  6. Competition • Two or more individuals attempting to use the same resource • Intraspecific competition • Among individuals within a population • Interspecific competition • Between different species

  7. Interspecific competition

  8. Competitive exclusion principle • Two species cannot occupy the same niche in the same community for an indefinite period • One species is excluded by another as a result of competition

  9. Some species reduce competition by resource partitioning • Competition among species is reduced by character displacement • Structural ecological and behavioral characteristics diverge where ranges overlap

  10. Resource partitioning

  11. Predation • Consumption of one species (the prey) by another (the predator) • Coevolution • Predator and prey both evolve more efficient ways to interact

  12. Ecological interactions among species

  13. Defenses • Mechanical defenses • Associating in groups • Cryptic coloration • Warning coloration • Müllerian mimicry

  14. Cryptic coloration

  15. Symbiosis • Mutualism • Both partners benefit • Commensalism • One partner benefits and the other is unaffected • Parasitism • One partner benefits while the other is harmed

  16. Mutualism

  17. Commensalism

  18. Parasitism

  19. Keynote species • Present in small numbers but are crucial in determining the species composition and ecosystem functioning • Dominant species • Affect the community because they are so common

  20. Species richness • Number of species within a community • Species diversity • Relative importance of each species within a community

  21. Effect of community complexity on species richness

  22. Ecological succession • Primary succession • Occurs in an area not previously inhabited • Secondary succession • Occurs where there is a pre-existing community and well-formed soil

  23. Intermediate disturbance hypothesis • Disturbance affects succession and species richness • Species richness is greatest at moderate levels of disturbance

  24. Intermediate disturbance hypothesis

  25. The nature of communities • Organismic model • Views a community as a superorganism that goes through stages of development (succession) • Individualistic model • Abiotic environmental factors are primary determinants of species composition • Organisms are independent

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