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Chapter 50 notes: Ecology and the Biosphere Ecology: the study of the interactions between organisms and their environments Interactions determine both the distribution an organism and their abundance. 3 main questions that Ecologists most; where do they live? Why do they live where they do? How many are there? Ecologists also study how the interactions between organisms and the environment affect number of species living in an area, the cycling of nutrients, and growth of populations. Ecology reveals the richness of the biosphere and provides a basic understanding that will help us sustain and conserve. Ecologist use observations and experiments to test explanations for the distribution and abundance of species and other ecological phenomena. Ecology and Evolutionary Biology are closely related sciences. Events that occur in the framework of ecological time (minutes, months, years) translate into effects over evolutionary time (decades, centuries, millennia) Ex. Predator-prey interaction where the selection for mice with fur coloration that enhances its camouflage The environment of any organism includes abiotic and biotic components. Abiotic factors: non-living, temperature, water, sunlight, wind, rocks, soil Biotic factors: living, interactions with other organisms, such as predation, parasitism, provide its food, competition or change its physical and chemical environment These factors lead to 2 questions: What environmental factors limit geographic range? (distribution) What factors determine its abundance? Sub-fields in Ecology: Organismal Ecology: How an organism’s structure, physiology, and behavior meet the challenges posed by the environment. Population Ecology: focuses on the factors that affect how many individuals of a particular species live in an area. Community ecology: deals with an array of interacting species in a community. Landscape Ecology: deals with arrays of ecosystems and how they are arranged in a geographic region. Research is focused on the factors controlling the exchange of energy, materials, and organisms among “ecosystem patches” making up the landscape or seascape. Ecosystem: consists of all biotic and abiotic factors and the entire community of species that exist in a certain area. Biosphere: is the global ecosystem – the sum of all the planet’s ecosystems. Ecology and Environmental issues: Environmentalism: advocating for the protection or preservation of the natural environment Ecological information is always incomplete> given what we do know about the interconnectedness of the biosphere, it would be prudent to follow “precautionary principle” “an ounce of prevention is worth a pound of cure” Dispersal: the movement of individuals away from centers of high population density from their area or origin. This contributes to the global distribution. Biogeography helps us understand the limiting factors for dispersal and distribution. Natural Range expansion: when organisms expand their range by moving into an area where they did not exist previously Species Transplants: for the transplant (accidental or intentional) to be successful, the species has to survive and reproduce. Often disrupt the communities and ecosystems where they have been introduced. Ex. Zebra Mussules Behavior and Habitat selection: Least understood process. Some organisms do not occupy all of their potential range even though they are physically able to disperse and the new habitat is suitable. When we can not determine if behavior is a limiting factor, we look at biotic and abiotic factors. Biotic and Abiotic influence on Aquatic Biomes: Aquatic Biomes account for the largest part of the biosphere in terms of area. Physical and chemical differences separate Marine biomes and fresh water biomes. Marine biomes generally have an average salinity level of 3%. Fresh water biomes generally have a salinity concentration of <1%. Marine Biomes: Intertidal zones: Oceanic Pelagic Zone: Coral Reefs: Marine Benthic Zone: The oceans (cover 75% of planet) evaporation provides most of the rainfall. Ocean temperature major effect on the world’s climate and wind patterns. Marine algae and photosynthetic bacteria provide most of the oxygen and consume huge amount of carbon dioxide. Freshwater Biomes: Lakes: Wetlands: Streams and Rivers: Estuaries: Freshwater biomes are closely linked to the soils and biotic components they pass through. Particular characteristics are influenced by speed of water flow and the climate Many aquatic biomes are chemically and physically stratified. Light is absorbed by both the water and photosynthetic organisms. Photic Zone: where there is sufficient light for photosynthesis. Aphotic Zone: where little light penetrates. Benthic Zone: bottom of all aquatic biomes, made up of sand and organic and inorganic sediments. Communities of organisms that occupy this zone are known as benthos. The major food source for benthos is detritus or dead/decaying organic matter which fall from the photic zone. Thermocline: found in oceans and most lakes, a narrow stratum of rapid temperature change which separates the warm upper layer from the cold lower layer of water. In both marine and fresh water environments, communities are distributed according to depth of water, degree of light penetration, distance from shore, and open water versus bottom. Climate has a great effect on organism distribution in terrestrial biomes. Climographs are used to look at temperature, and precipitation in a particular region. Annual averages for temp and rain fall are reasonable well correlated with biomes that exist in different regions. Other factors play a role as well: patterns of moisture, and temp, bed rock for mineral nutrient availability and soil structure which can determine what kind of vegetation will grow. General Features of terrestrial biomes: Most terrestrial biomes are named for major physical or climatic features and for their predominant vegetation. Vertical stratification is an important feature as well as the shapes and sizes of plants which define the layering. Forests: upper canopy – lower tree stratum – shrub understory – ground layer herbaceous plants – forest floor (litter layer) – root layer. Stratification of vegetation provides many different habitats for animals – well defined feeding groups from bats and birds that feed above the canopy to worms and arthropods that forage in the litter. Ecotone: area where different biomes feed into each other without sharp boundaries. May be wide or narrow Biomes are dynamic, disturbance rather than stability is the rule. As a result, biomes exhibit patchiness with several different communities represented in any particular area. Human activity has altered the natural patterns of periodic disturbance. Ex. Fire control and population encroachment along the east coast (broad leaf forest) Major terrestrial biomes: Tropical forests: Desert: Savanna: Chaparral Temperate grasslands: Coniferous forest: Temperate Broadleaf forest Tundra: