1. Community ecology Chapter 56

2. What is a biological community? Community includes all its species living together. Community includes all its species living together. Defined by species richness (the number of species present) or primary productivity (the amount of energy produced) Defined by species richness (the number of species present) or primary productivity (the amount of energy produced) Assemblage defines a part of the community or connotes a portion of community Assemblage defines a part of the community or connotes a portion of community

3. Different concepts over biological communities Individualistic concept- an aggregation of species that happen to occur together at one place Individualistic concept- an aggregation of species that happen to occur together at one place Holistic concept-is an integrated unit composed of species that work together as part of functional whole Holistic concept-is an integrated unit composed of species that work together as part of functional whole Ecotones are transitional zones where environmental conditions keep rapidly changing and species from each environment overlap. Ecotones are transitional zones where environmental conditions keep rapidly changing and species from each environment overlap.

4. What is the Ecological Niche Concept? Niche- Sum of all the ways in which a species can use its environmental resources. Niche- Sum of all the ways in which a species can use its environmental resources. Interaction between species can be positive or negative Interaction between species can be positive or negative Interspecific competition – two species attempting to use same resources (less availability) Interspecific competition – two species attempting to use same resources (less availability) Interference competition – accessing a resource involves physical interactions example defending a territory Interference competition – accessing a resource involves physical interactions example defending a territory Exploitative competition – consuming same resources Exploitative competition – consuming same resources

5. What are the two concepts of Ecological Niche? Fundamental niche describes capacity of a species to use its resources in absence of intervening factors. Fundamental niche describes capacity of a species to use its resources in absence of intervening factors. Realized niche are actual environmental conditions that allow establishment of stable population. Realized niche are actual environmental conditions that allow establishment of stable population. Competitive exclusion states that if two species occupy same area and compete for same resource, then one will be eliminated (figure 56.5) Competitive exclusion states that if two species occupy same area and compete for same resource, then one will be eliminated (figure 56.5) Resource partitioning occurs in similar species that occupy same geographic area to reduce competitive pressure (figure 56.6) Resource partitioning occurs in similar species that occupy same geographic area to reduce competitive pressure (figure 56.6)

6. Co-evolution of Predator-Prey Relationships Predation is the consumption of one species by another Predation is the consumption of one species by another Pressures on both prey and predator to win survival Pressures on both prey and predator to win survival Plant and animal prey evolve chemical defenses – accumulation of secondary chemical compounds in plants-deter some herbivores – some butterflies feed – accumulate those chemical compounds-deter their predators (birds) Plant and animal prey evolve chemical defenses – accumulation of secondary chemical compounds in plants-deter some herbivores – some butterflies feed – accumulate those chemical compounds-deter their predators (birds)

7. Different animal adaptations to defend against predators Bees, wasps, scorpions use chemicals to catch their prey and defend from predators Bees, wasps, scorpions use chemicals to catch their prey and defend from predators Warning or defensive coloration in insects feeding on milkweed plants that use poisons and stings to repel predators Warning or defensive coloration in insects feeding on milkweed plants that use poisons and stings to repel predators Batesian mimicry occurs when palatable species looks like distasteful species Batesian mimicry occurs when palatable species looks like distasteful species Mullerian mimicry occurs when two distasteful species look similar (figure 56.14) Mullerian mimicry occurs when two distasteful species look similar (figure 56.14)

8. What is ecological succession? Succession is a process in which communities change over time and species alter their habitat and resources facilitating other species. Succession is a process in which communities change over time and species alter their habitat and resources facilitating other species. Primary succession occurs on bare, lifeless substrate. Example rocks or open water Primary succession occurs on bare, lifeless substrate. Example rocks or open water Secondary succession occurs in areas where existing community has been disturbed but organisms still remain. Secondary succession occurs in areas where existing community has been disturbed but organisms still remain. Plant and animal succession affect each other Plant and animal succession affect each other Species richness may increase and ultimately decline Species richness may increase and ultimately decline

9. What is ecological disturbance? Disturbance can be widespread or local, examples: fire, drought and floods Disturbance can be widespread or local, examples: fire, drought and floods Intermediate levels of disturbance may maximize species richness Intermediate levels of disturbance may maximize species richness Patches of habitat will exist at different successional stages Patches of habitat will exist at different successional stages Prevent communities from reaching final stages of succession Prevent communities from reaching final stages of succession

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