Population Interactions Ch. 51

1. Population InteractionsCh. 51

2. Ecological Community • Interactions between all living things in an area • Coevolution changes encourages by interactions between two or more species • Predator vs. Prey • Herbivore vs. Plant • Food Availability creates complex interactions: • Optimal Foraging Theory animal must balance the energy spent to get food with the energy they get from eating it; determines diet • Specialist eat one or few types • Generalist eat almost anything

3. Arms Race • Prey must adapt methods to protect themselves if they are to survive • Hiding places; physical defenses; poisons • Aposematic coloration bright, contrasting color patterns that act as a warning of poison • Predators must learn to over come these methods too • Recognize poisonous prey; hunting skills; immunity to poisons • Cryptic coloration camouflage to help hide predators and prey

4. Copy Cat • Mimicry resembling the appearance of a another species to gain an advantage • Batesian harmless species mimics a dangerous species • Mimic gains protection but does not commit energy like the model does • Mullerian dangerous species have similarities; predators learn of danger much faster

5. Fight for the Right to Survive • Interspecific competition competing between different species • IntRAspecific competition inside a population of one species • Interference species directly limit access to resources • Lions chase away hyenas • Exploitative species lower amount of resources so they are harder to find • Birds eat seeds so it is harder for squirrels to find them • Competitive Exclusion Principle if two population require the same limited resources in the same way, one will destroy the other

6. You Need a Niche • Niche specific way a species interacts with its environment • All successful businesses need a market in order to survive • Ecological niche the food type, amount, and space required for a species to survive • Fundamental all possible resources that CAN be used • Realized all possible resources ACTUALLY used • Competition can occur when fundamental niches overlap

7. Cant We All Just Get Along • Not all overlapping parts of niches lead to competition • All animals breath air but rarely have to compete for it • Resource partitioning different species can use the same resources but can get them or use them in different ways • Birds species can feed on the same insects but get them different parts of the tree • Character Displacement • Sympatric species living in the same area are more morphologically different • Darwin’s Finches • Allopatric species living in different areas are less morphologically different

8. Symbiotic Interactions • Symbiosis physical ecological interactions • Commensalism one species benefits and one species is not affected • Grass eaters stir up insects that birds will eat • Mutualism both species benefit • E. coli in your intestine gets nutrients from us and gives us vitamins • Parasitism one species benefits (parasite) and one species is negatively affected (host) • Tapeworm takes nutrition from our intestine and decreases our health • Endoparasites live inside the body • Ectoparasites live outside the body

9. Defining A Community • Some see communities as “super-organisms”; species in the community are so well connected they require each other to exist and to exist in certain amounts • Species composition could reach equilibrium and shifts with major changes • Others think communities constantly change and have no strict boundaries or composition • Some biomes do have clear boundaries though; Water vs. Land, Aerobic vs. Anaerobic • Ecotones edges where communities meet; full of biodiversity • ESSAY!!! • Explain which of these ideas you most agree with; support with reference material

10. Species Diversity • Communities are built around a foundation species (one that stabilize environment) • Most often trees/plants • One or two dominate species appear (majority of biomass) • Species richness # of species present • Relative abundance # in each species population • Both together make Species Diversity greater the diversity the more stable the environment

11. Movement of Energy • Food Web showing all the predator/prey connections in a community; made of all possible food chains • Trophic levels where in the chain a species belongs • Primary producers all plant life and photosynthesizers (autotrophs) • Primary consumers; herbivores (heterotrophs) • Secondary consumers; carnivores/omnivores • What is the most important group? • Recyclers Detritivores (animals that eat dead material) and Decomposers (bacteria that eat dead material)

12. Complex Limits • If species richness and diversity makes communities more stable, why is there not more diversity in nature? • Interspecific competition allows only a small number of species to survive • What can fight against the selective power of competition? • Predator/prey interactions • Predators can keep prey in check that are competitors for other species • Keystone species a species, that if removed, would have the most dramatic effect on a community’s structure

13. Dealing with Disturbances • A popular theory is that communities will grow to equilibrium points and only shift when disturbances ruin their equilibrium • An area experiences flooding after heavy rains throughout the year; r-selected or K-selected dominated? • r-selected; community change too often and too quickly for K-species to adapt but r-selected can live their how life cycle between floods • An area the experience little disturbances would be K-selected dominated; r-selected kept in check by K-selected predators • What amount of disturbance creates the most diversity? • Intermediate disturbance hypothesis common but mild disturbances allow mixing of r-selected factors but K-selected can still survive

14. Ecological Successions • Disturbances cause changes (successions) in community composition • Primary Succession creating an ecosystem from an area with no soil (after a volcano erupts or new land forms) • Lichens live on water and nutrients from rock bed; secret an acid which degrades rock into soil • Mosses live and die to build up nutrients • r-select plants (grass, ferns) move in and continue process • K-selected plants (trees) move in and allow large community to exist • Climax community fully plant dominate community; stable until another disturbance comes

15. Other Successions • Disturbances like fire or storms can cause a Secondary Succession • Disturbance removes large percent of plant community but rich soil remains • New species fill in spaces in community rapidly • Aquatic Succession lakes and rivers fill in to become swamps; then rapid plant growth dries up area becoming a new meadow or forest

16. Are Successions Predictable • What determines how a community will turn out as Successions occur? • Facilitation hypothesis existing species make the area more suitable for other species later on • Natural order to growth (lichens make soil for mosses that build soil for plants) • Inhibition hypothesis existing species prevent new species from joining by filling their niche • No order; randomly based on which species takes niche first • Tolerance hypothesis inferior species are replaced by superior ones • Competition decides as resources are limited • Most likely a combination of all 3 and several other factors

17. Are Successions Predictable • Suggested Homework: • Test Your Knowledge • Actual Homework: • Design an Experiment • Apply Evolutionary Thinking • Due Thursday