1. 1 Community Ecology Chapter 54

2. 2 Biological Communities A community consists of all the species that occur together at any particular locality.

3. 3 Fundamental and Realized Niches An organism’s niche is the total of all ways it utilizes the resources of its environment. – fundamental - entire niche potentially available to an organism – realized - actual niche utilized by an organism Habitat is the place where an organism lives.

4. 4 Realized Niche Interspecific competition - Occurs when different species attempt to utilize the same resource. – interference - individuals fighting over the same resource – exploitative - individuals utilizing shared resources

5. 5 Principle of Competitive Exclusion The principle of competitive exclusion states that no two species utilizing the same niche can coexist indefinitely. – one will eventually eliminate the other  Gause’s Paramecium experiments

6. 6 Detecting Interspecific Competition Negative effects of one species on another do not automatically indicate competition. – Presence of one species may attract a predator that consumes both, causing one species to have a lower population size than the other.  must always look at underlying ecological mechanisms

7. 7 Predation and Prey Populations Predation occurs when one organism consumes another. – provides strong selective pressure on prey populations  Any physiologic characteristic or behavior that would decrease the probability of capture should be strongly favored.  increased fitness

8. 8 Plant Defenses Against Herbivores Morphological – thorns, spines, etc. Chemical – secondary chemical compounds Evolutionary response of herbivores – Certain groups of herbivores are associated with each group of plants protected by a particular secondary compound.  coevolution

9. 9 Animal Defenses Against Predators Some animals that feed on plants rich in secondary compounds receive an extra benefit. – caterpillars that feed on members of the milkweed family

10. 10 Animal Defenses Against Predators Chemical defenses – poisons and stings Defensive coloration – aposematic coloration (warning coloration)  individuals advertise poisonous nature – cryptic coloration  camouflage (blending coloration)

11. 11 Mimicry Batesian mimicry – Palatable insects resemble brightly colored, distasteful species. Mullerian mimicry – Unrelated protected species resemble one another.  predators learn more quickly

12. 12 Coevolution and Symbiosis Coevolution involves long-term mutual evolution of two or more species. – predator-prey interactions – symbiotic relationships  two or more kinds of organisms live together in permanent relationships  commensalism, mutualism, and parasitism

13. 13 Commensalism One species in symbiotic relationship benefits while the other is neither helped or hurt. – tropical fish and sea anemones

14. 14 Mutualism Both species in relationship benefit. – mutual cooperation  ants and acacias

15. 15 Parasitism Parasite benefits while inflicting some form of harm to the prey. – ectoparasites  external parasites - lice – endoparasites  internal parasites

16. 16 Interactions Among Ecological Processes Keystone species – Species that have a particularly strong effect on community composition.  top predators

17. 17 Succession Succession is the process of ecosystems changing from a simple to a more complex structure. – primary succession - occurs in bare areas – secondary succession - occurs following disturbance Succession occurs because species alter the habitat and available resources in ways that favor other species.

18. 18 An ecosystem includes all the organisms living in a particular place, and the abiotic environment in which they interact. Producers Autotrophs - capture light energy and manufacture own chemical energy Consumers Heterotrophs - must obtain organic molecules from autotrophs

19. 19 Trophic Levels - Food Chain Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Tertiary consumer Primary consumer Primary producer Secondary consumer

20. 20 Trophic Levels Trophic level refers to the feeding level of an organism. Organisms from each trophic level constitute a food chain.

21. 21 The Energy in Food Chains Second Law of Thermodynamics food chains are generally limited to 3 or 4 steps (trophic levels) ultimately determined by the amount of sunlight On average, 10% of the organic matter (energy) transfers from one trophic level to the next.

22. 22 Interactions Among Trophic Levels Trophic cascading effect of one trophic level flows down to lower levels. (top-down effects) Bottom-up effects productivity of an ecosystem is low, herbivore populations will be too small to support any predators.

23. 23 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Vegetation Herbivores Productivity

24. 24 Interconnected food chains constitute a food web.