EcologyIntroductionLevelsPopulation DynamicsPopulation Age Structurer-Selected vs. K-Selected SpeciesCommunity InteractionsCompetitionPredation and ParasitismEvolutionary Arms RaceMutually Beneficial InteractionsCommunity SuccessionMore on SuccessionEnergy Flow in EcosystemsEnergy PyramidNutrient CyclesCarbon CycleNitrogen CycleHydrological CycleClimate and AtmosphereOcean CirculationTerrestrial BiomesTundraTaigaTemperate ForestGrasslandsTropical Rain ForestDesertAquatic EcosystemsOceansEcologyIntroduction•Ecology is the study of interactions between species and with the non-living environment.Levels•Population: all members of one species living in a given area.•Community: all living organisms (many different species) living in a given area•Ecosystem: the organisms in a given area along with the non-living environment (rain, temperature, soil, etc.). –large scale ecosystems are called biomes.•Biosphere: the entire living world and its non-living environment. The portion of Earth that supports life. Roughly 2 miles below the surface to 6 miles above the surface, over the entire planet.Population Dynamics•How a species is distributed and how it changes over time. •populations can stay steady with time•or, they can undergo exponential growth (a J-shaped curve, 1-2-4-8-16-32-...). Ends up increasing very quickly, but the rate can vary. The doubling time of a population is the critical parameter: How long it takes to double the population size.•or, they can grow exponentially for a while and then level off as limits are approached (logistic growth). •carrying capacity : how many of a species can a given area support. If the population grows much past the carrying capacity, it will have a die off.–limiting factors: food, waste disposal, predators, nesting/mating sitesPopulation Age Structure•Relative number of individuals of different ages and sexes.•How many are of reproductive age vs. before it or after it?•predicts future structure: groups move up in age but relative sizes of groups stays the same.r-Selected vs. K-Selected Species•Two fundamentally different strategies.•K-selected, or equilibrium species. Produce a small number of offspring, enough to replace each generation or have a slow population growth rate. –Lots of energy into each offspring. –Late maturity, many live to old age, parents care for their offspring. –Population size stays near the carrying capacity of the environment. –Humans and most other large mammals are K-selected.•r-selected, or opportunist species. Produce vastly more offspring than can survive. –If times are good, many will survive and if times are bad only a few will survive. –Allows rapid exploitation of new resources. –Small organisms, early maturity. cheap to make, short life expectancy, no parental care.–Mosquitoes, flies, many fishCommunity Interactions•A community is all the organisms that live is a particular region.•Habitat: physical surroundings inhabited by a community of organisms. The type of place where they live. Influenced by temperature, soil, rainfall, etc. •Niche. How an individual species makes a living: What it eats, where it lives, how it competes with other species. its food resources, mating and offspring rearing resources, defenses against predators and diseases. –All species in a community share a common habitat, but each species has its own niche. –fundamental niche vs. realized niche. Fundamental niche is what a species could occupy in the absence of competition and other constraints. realized niche is the niche the species actually sues. realized niches change over time as the species responds to pressures. •The important thing about the niche is that it is heavily influenced by interactions between species.Competition•Different species often have similar requirements for resources, but never as similar as members of the same species.–competition within a species is the driving force in microevolution: individuals with more fit alleles take over the population.•competitive exclusion: each niche can have only 1 occupying species. Others will be driven out. –the diagram: 2 species of paramecium will grow well alone, but one dies of if they are mixed. •resource partitioning: dividing up a niche as a method of co-existingPredation and Parasitism•predator-prey cycles: too many predators means prey population size crashes, leading to predator crash.•successful parasites don’t kill all of their hosts.•large amount of evolutionary change driven by arms race between predators (or parasites) and preyEvolutionary Arms Race•Co-evolution: species influence each other’s ability to survive and reproduce.•Camouflage: hiding from predators•Defenses: painful sting, sharp claws, bad taste.•Warning coloration: Warn the predator about prey’s defenses so it learns to stay away.•Mimicry as a tool: fool predators by looking like another species that is unpleasant or dangerous to attack.•Of course, predators evolve ways to get around these defenses: sharper senses, chemical detoxification.Mutually Beneficial Interactions•Symbiosis: two species living together. Some symbioses are mutually beneficial and others (parasitism) are not.•mutualism: both species benefit. –Pollination of flowers is a good example: the flower supplies nectar (sugary nutrients) and the bee spreads the flower’s pollen from one individual to another. Many such interactions between flowering plants and their pollinators.–Nitrogen-fixing bacteria invade root nodules on certain plants: the plants get fixed nitrogen and the bacteria get nutrients and shelter from oxygen, which would kill them.•commensalism: one benefits, the other neither gains nor loses. –Birds nesting in trees. The birds benefit, but the trees are unaffected.Community Succession•How does a community come into existence? •Classical model of succession: –a barren lifeless area starts out with a few very tough species–These pioneer organisms improve conditions so that other species can move in. –a series of different communities takes over in turn, each one improving conditions for the following community–ends in a steady state, self-sustaining climax community•Example:–bare rock is colonized by lichens and mosses. As they decay, they build up a thin layer of soil. –Grasses and other small plants can grow on this thin soil. –They in turn improve the soil,