UNIT IV ECOLOGY Lecture 21 Ecology and Plant succession Ecology study of effects of environment on living organisms and living organisms on the environment 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 Ecosystem Communities with all its living organisms biotic and non living organisms abiotic Biotic organisms interact in food chain or food web Control structure and species composition of community through Physical factors light wind and humidity Chemical factors nutrients and pH o Producers photosynthetic 1st order consumers herbivores 2nd order consumers carnivores o Trophic level each step in food chain energy is lost at each level o 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 substances Biogeochemical cycles o Carbon cycle o C02 enters plants through photosynthesis carbon is released through respiration or combustion fossil fuels were formed o Water cycle falls into river streams oceans o Nitrogen cycle o Water enters atmosphere as vapor from land transpiration from plants vapor condenses rain o 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 down Climax community relatively stable community at the end of succession In equilibrium with environment o o Permanent until major change o Varies depending on conditions Types of succession 1 Primary succession when plants become established on land completely devoid of soil and vegetation a Soil portion of earths surface of disintegrated rock and organic materials humus i Provides essential nutrients water minerals to all plants ii Soil texture 3 types of particles sand silt clay most important holds nutrients iii Organic matter humus is decomposing organic matter in soil iv Soil pH acid low or basic high influences soil fertility and nutrients best is slighting acidic b Forest habitats lichens mosses grasses shrubs trees c Begins as pioneer species for inhabitants invade bare rock and form soil climax community is spruce fir and birch forest d Each stage prepares the way for the next invasion of species 2 Secondary succession natural forces human intervention destroy existing vegetation fire flooding logging agriculture community begins secondary succession back to climax a Since soil is in place 5 10x faster than primary b Abiotic factors affect nature of plant community weather temp humidity i Tropical rainforests vegetation creates rainfall through plant transpiration when trees are removed rainfall stops land becomes arid resulting climax desert shrubs Lecture 22 Terrestrial Biomes Biome 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 Role of Climate o Daily and seasonal cycles influence prevailing o Climate is global and ever changing differences in atmospheric heating create winds drive global patterns of atmospheric circulation o 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 Pole 1 Tundra 2 Boreal Forest taiga a arctic b Climate very cold and dry little precipitation c Soil permafrost d Plants No trees many low shrubs and herbs grass like lichens and mosses e Animals Migratory birds wolves fox polar bear rain deer f Sensitive to human disruption takes a long time to recover a arctic circle Alaska Canada and great lakes b Climate severe winters extreme cold and little precipitation c Soil wet deep permafrost nutrient poor may be acidic d Vegetation trees dominate especially pines conifers fir spruce birch aspen e Animals caribou wolves fox bear moose mink and migratory birds f Human impact Hunting mineral exploitation and lumbering 3 Temperate deciduous forest a Eastern North America b Climate higher precipitation rain extreme temperatures hurricanes and freezing cause damage c Soil more acidic and fertile lower layer rich in clay top rich with decayed organic matter d Plants deciduous leaves fall off seasonally some conifers pines e Animals deer moose buffalo bear all diminishing due to hunting raccoon opossum skunks bobcats fox wolves resident songbirds and waterfowl migrant birds too f No undisturbed forests left due to extensive logging clear cutting introduction to exotic species has altered flora 4 Grasslands a Widely scattered throughout the world North American Prairie Great Plains b Climate very low rainfall with warm summers and cool winters c Soil generally fertile deep and rich d Plants members of the grass family usually one or two dominate i Rhizomatous to spread out and are wind pollinated deep roots ii Adapted to fires and drought iii Some trees and shrubs e Animals bison gophers coyote prairie dogs squirrels f Human impact majority of grassland used for farming cultivated food cereals overgrazing urbanization exotic weeds major problem 5 Deserts a North America new Mexico Arizona southern California northern Mexico b Climate low precipitation hot day cold nights c Soil low organic content dryness prevents decomposition sandy to rocky high mineral content often toxic levels d Hot low Sonoran desert Cold high Utah Great Basin e Vegetation sparse plant cover i Xerophytes adapted to dry arid regions strategies to conserve water f Animals hard to find reptiles rodents g Human impacts intense grazing has destroyed palatable vegetation for sheep and cattle poisonous plant invasion and exotic weeds 6 Chaparral a North America California Mexico called Mediterranean b Climate cool and wet in winter rains Nov to April hot and dry otherwise c Soil shallow and rocky generally poor d Plants dominant shrubs like chamise and Manzanita oaks and pines evergreen or summer deciduous trees lack of understory e Animals diversity of ground birds deer and small mammals endemic plants animals f Human impact intense grazing as resulted in extinction suburban sprawl fire suppression