UNIT IV: ECOLOGYLecture 21: Ecology and Plant successionEcology: study of effects of environment on living organisms and living organisms on the environment-Organisms – populations – communities – ecosystems - biosphere-Population: members of a single species living together-Habitat: location where the population is found-Niche: functional role an organism plays in the ecosystem-Dominant Species: most influential in community ex. Redwood forest-Control structure and species composition of community through…-Physical factors: light, wind, and humidity-Chemical factors: nutrients, and pH-Plant Ecology: the interactions among plants and between plants and the environment-Plant Community: different populations of plants living together in the same geographical areaEcosystem: study of environment-Communities with all its living organisms (biotic) and non-living organisms (abiotic)-Biotic: organisms interact in food chain or food webo Producers (photosynthetic.)  1st order consumers (herbivores)  2nd order consumers (carnivores)o Trophic level: each step in food chain – energy is lost at each levelo Food web (realistic): multiple interactions between several food chains – consumers have alternate food choices-Abiotic: non living components of the environment: climate, light, soil, inorganic substanceso Biogeochemical cycleo Carbon cycleo C02 enters plants through photosynthesis – carbon is released through respiration or combustion –fossil fuels were formedo Water cycleo –Water enters atmosphere as vapor from land/transpiration from plants – vapor condenses – rain falls into river, streams, oceanso Nitrogen cycleo Nitrogen gas is fixed by bacteria – plants assimilate N and incorporate it into organic nitrogen – animals assimilate N by ingesting plants – animal waste and organic nitrogen compounds are broken downBiosphere: areas on Earth in which organisms are found-All of the communities on earth-Biomass: the organic material in living organisms-Ecosphere: interactions among Earths biosphere, atmosphere, water and land-Greenhouse effect: human upset balance of carbon cycleo Global deforestation - more C02 released due to burning fuelso Result: 25% increase in global C02o Carbon dioxide acts as a heat trap, capturing sunlighto Consequence: global warming, less agricultural areas, diseases such as malaria, ocean level increase (floods,hurricanes)o Global warming: C02 and other gases trap solar energy, reradiating it back to the earth as heat, warming the atmospherePlant Succession: series of predictable changes over time in the kinds of plants growing in an area-Ecosystems mature and change with time – predetermined by the physical parameters in the environment-As ecosystems age, organisms change  until a stable community formso Initial stages: unstable, high rate of replacemento Later stages: more stable, low rate of changeClimax community: relatively stable community at the end of successiono In equilibrium with environmento Permanent until major changeo Varies depending on conditionsTypes of succession:1) Primary succession : when plants become established on land completely devoid of soil and vegetationa. Soil: portion of earths surface of disintegrated rock and organic materials (humus)i. Provides essential nutrients (water/minerals) to all plantsii. Produced by the living environment, influenced by climate, topography, parent material, timeiii. Parent material: soil particles of naturally occurring inorganic materialiv. Soil texture: 3 types of particles – sand, silt, clay (most important, holds nutrients)v. Organic matter: humus is decomposing organic matter in soilvi. Soil pH: acid (low) or basic (high) influences soil fertility and nutrients – best is slighting acidicb. Forest habitats: lichens  mosses  grasses  shrubs  treesc. Begins as pioneer species, for inhabitants, invade bare rock and form soil – climax community is spruce-fir and birch forestd. Each stage prepares the way for the next invasion of species2) Secondary succession : natural forces/human intervention destroy existing vegetation (fire, flooding, logging, agriculture) – community begins secondary succession back to climaxa. Since soil is in place, 5-10x faster than primaryb. Abiotic factors affect nature of plant community – weather, temp, humidityi. Tropical rainforests: vegetation creates rainfall through plant transpiration – when trees are removed, rainfall stops, land becomes arid – resulting climax – desert shrubs-Natural systems maintain themselves, whereas disturbed systems cannot-Human influence on succession: knock out climax communityEx. maintaining a greed, weed free law: constant battle with nature – planting grass, mowingLecture 22: Terrestrial BiomesBiome: largest terrestrial divisions of the biosphere – large, distinct ecosystems climax communities for huge regions of the land – recognized and defined by distinctive vegetation and animal life-Controlled by…o Temperatureo Precipitation: annual and seasonal distributiono Wind, humidity, light, fire, soil type-Role of Climate:o Daily and seasonal cycles influence prevailingo Climate is global and ever changing – differences in atmospheric heating create winds, drive global patternsof atmospheric circulationo Seasons are determined by the tilt of the earth-Elevation/altitude: In NA weather patterns move from west to east-Precipitation: influenced by physiographic features, mountains, rivers, oceans-Elevation: altitude influences biomes, cooler temperatures high in the mountains favor biomes similar to biomes near North Pole1) Tundra a. Northernmost land biome: around the arcticb. Climate: very cold and dry, little precipitationc. Short growing seasond. Soil: wet, shallow, or permanently frozen called permafroste. Plants: perennials (20-100 years) and shorti. No trees, many low shrubs and herbs, grass –like (lichens and mosses)ii. Strategies to deal with cold and windf. Animalsi. Migratory birds, wolves, fox, polar bear, rain deerg. Very low biodiversity and productivityh. Sensitive to human disruption – takes a long time to recover 2) Boreal Forest (taiga): 17% of earths land surfacea. Area near the arctic circle, Alaska, Canada and great lakesb. Climate: severe winters, extreme cold and little precipitationc. Short growing season, snow is commond. Soil: wet, deep permafrost, nutrient poor, may be acidice. Vegetation: trees dominate, especially pines