Chapter 55 Community Ecology

1. Chapter 55 Community Ecology Biology 101 Tri-County Technical College Pendleton, SC

2. Some Key Terms • Population = localized group of individuals belonging to the same species • Community = assemblage of species close enough for potential interaction • Habitat = place or environment where an organism naturally or normally lives and grows • Niche = habitat supplying the factors necessary for existence of organism OR ecological role of an organism in a community (especially in regard to food consumption)

3. More Key Terms • Resource = anything directly used by organism that can potentially lead to growth of population and whose availability is reduced when it is used • Food and space • Limiting resource = resource whose supply is LESS than the demand made upon it by organisms • Generally are subject to depletion and regenerate slowly

4. Symbiosis • Defined as “living together” • Predator-Prey • Predator is organism that kills and eats • animals by animals/eating of plants • Prey (host) is organism consumed as energy source • Serves as agent of natural selection as well as for mortality

5. Predator-Prey Visual

6. Symbiosis II • Parasitism describes organism that lives on or in a host • Not wise to kill the host • Microparasites (viruses, bacteria, & protists) • Very short generation times & host may harbor 1000s to millions • Best defined as one benefits and one is harmed • Competition = use of same resource by two or more species when resource is present in insufficient supply for combined needs of both • Both are harmed by competition

7. Symbiosis III • Mutualism = both participants BENEFIT • Commensalism = occurs when one participant benefits and the other is unaffected (neither benefits or is harmed) • Amensalism = occurs when one participant is harmed but the other is unaffected

8. Species Richness and more… • Species richness of a community describes the number of species that live there • Keystone species = species whose influences on ecological communities ARE greater than would be expected • Influences species richness, flow of energy, and materials in an ecosystem • Succession = sequence of change in species composition of a community

9. Competition • Intraspecific competition defines competition among individuals of same species • May result in reduced growth & reproductive rates for some, exclude some from better habitats, and cause death in others • Interspecific competition defines competition among individuals of different species • Same results as intraspecific but may keep entire species out of habitats where they cannot compete successfully in phenomenon called competitive exclusion

10. Mutualism • Most complex and important symbiosis between members of different kingdoms or domains • Mycorrhizae, lichens, animals & protists (termites and corals) • Animal-animal (ants and aphids and the milking process) • Plants-animal (trees and ants; angiosperms and pollen)

11. …and finally, brethen • Commensalism (cattle egrets and grazing animals) • Amensalisms are widespread and important in nature • Mammals and watering holes; trees dropping leaves and branches

12. A form of flattery… • Mimicry is an evolved resemblance to some inedible or unpalatable item • Batesian mimicry = palatable species mimics an unpalatable or noxious one • Spiders that mimic wasps; insects that mimic bees or wasps • Works because predator that captures individual of unpalatable/noxious species learns to avoid any prey of similar appearance

13. Mimicry II • Mullerian mimicry = convergence over evolutionary time in appearance of two or more unpalatable species • All species benefit when inexperienced predators eat individuals of any species because predators learn all species of similar appearance are unpalatable • Tropical butterflies/bees and wasps

14. Plant Defenses • Tough leaves, hairs, spines to reduce predation are physical defenses • Most plant tissue also contains defensive chemicals called secondary compounds • Are of two general types: acute toxins and digestibility-reducing compounds • Acute toxins disrupt herbivore metabolism • nicotine interferes with nerve impulse transmission • hallucinogens cause seriously distorted view of environment

15. Defenses II • Imitate insect hormones and prevent insects from completing metamorphosis • Unusual amino acids that become incorporated into herbivore proteins and interfere with their functioning • Other toxins defend against viruses/bacteria • Digestibility-reducing compounds make plant tissue more difficult to digest

16. Defenses III • Most common are tannins which are present in leaves of some herbaceous and most woody plants • When released by grazing, tannin binds to proteins in leaf and to herbivore digestive enzymes reducing ability of herbivore to extract proteins from leaves • Why eat it if one cannot get any benefit from it? • Could continue, but….

17. Succession • Succession = sequence of change in species composition of a community • Primary succession = establishment of organisms on newly available sites that previously had NO organisms • retreat of glacier; new volcanic island • Secondary succession = organisms reestablish themselves on disturbed sites where some organisms survived the disturbance

18. Succession and more • fires, earthquakes, tidal waves • text gives decomposition of dead bodies of plants and animals • Climax community = relatively stable ecological stage or community (especially of plants) that is achieved through successful adjustment to an environment • Especially applicable to final stage in ecological succession

19. The love buzz…