General Ecological Principles

Transcription

1 General Ecological Principles as far as we know; only earth harbors life even on earth, life is contained within a thin veneer near the earth s surface = biosphere all life evolved on earth and as such are subjected to similar range of conditions What characteristics of the biosphere make it so favorable to life? environmental characteristics of the biosphere remain: fairly constant over the surface of the earth and over time temperatures range over ~100º in most places liquid water in universe can vary over millions of degrees atmosphere ideal amt of sunlight and solar heating changes due to weather are only a small % of this amts of O 2 and CO 2 constant over millions of years main variable is water vapor gravitational force constant chemical composition of open ocean salinity fairly constant ppt, similar proportions of salts these conditions have molded species along similar patterns one of the main characteristics of life is that living organisms are constantly interacting with their environment and with each other the relatively small variations within these environmental factors defines the natural habitats and ranges of a species biosphere: the total living world and all aspects of the environment with which life directly interacts ecology: the study of organisms interactions with their environment & with each other ecosystem is a portion of the biosphere with similar environmental conditions Ecology: General Ecological Principles, Ziser, Lecture Notes,

2 supporting a characteristic and distinctive group of species other terms for ecosystems: biomes, ecoregions, life zones, etc the structure of an ecosystem consists of both biotic and abiotic parts the function of an ecosystem can be studied at various biotic levels or as interactions between abiotic and biotic components Ecosystem Structure 1. Biotic Levels = living organisms a. Individual Organisms: ones directly affected by environmental factors such as climate, temperature, seasonality, light, food, etc individuals vary (due to genes) and vary in their ability to survive and adapt to changing environmental conditions their success is measured by their ability to produce offspring struggle for existence survival of the fittest Ecosystem Processes most affecting Individual Organisms: tolerance ranges and limiting factors nutrient requirements, oxygen requirements b. Populations: self contained group of interacting individuals of the same species each population consists of dozens to thousands of individual organisms Ecosystem Processes most affecting populations: feeding strategies: herbivores, carnivores, omnivores, detritivores, etc immigration and emigration seasonal migrations c. Communities: self contained group of all interacting species within an ecosystem made up of many populations Ecosystem Processes most affecting communities: microhabitat preferences: soil, benthos, plankton, eipfauna, infauna biogeochemical cycling symbioses: mutualism, commensalism, parasitism Ecology: General Ecological Principles, Ziser, Lecture Notes,

3 2. Abiotic Components = nonliving portion of biosphere a. Lithosphere: solid: rocks, soil particles, sediments,etc Ecosystem Processes affecting lithosphere: biogeochemical cycling weathering: mechanical & chemical soil formation and structure b. Hydrosphere: liquid: water in every form; oceans, groundwater, rivers, lakes, rainfall, ice Ecosystem Processes affecting hydrosphere: biogeochemical cycling: the water cycle precipitation & rainfall erosion discharge and water velocity c. Atmosphere: gases: primarily nitrogen, oxygen and carbon dioxide gas with mixture of other gaseous compounds Ecosystem Function Ecosystem Processes affecting atmosphere: biogeochemical cycling: nutrient cycling weather phenomena: temp, storms, nitrogen fixing oxygen availability A. Individual Requirements Tolerance Ranges and Limiting Factors eg. humans vs brine shrimp eg phosphorus and nitrogen eg macronutrients and micronutrients All organisms respond best to an optimum range of conditions Most organisms have a relatively narrow tolerance range B. Habitat Specific Adaptations there are 3 major kinds of ecosystems 1. marine ecosystems 2. freshwater ecosystems Ecology: General Ecological Principles, Ziser, Lecture Notes,

4 3. terrestrial ecosystems each imposes several major constraints on the organisms that live their C. Feeding Strategies: herbivores, carnivores, omnivores, detritivores D. Production & Productivity 1. respiration vs production 2. gross vs net productivity 3. primary & secondary productivity E. Trophic Levels and Food Webs: producers consumers decomposers F. Pyramids of Numbers and Biomass G. Biogeochemical Cycles H. Energy Flow & Trophic Structure factors that limit productivity ecological efficiency and the "10% rule" length of food chains I. Interactions all organisms interact with other organisms in various ways 1. Individual Interactions: a. symbioses: mutualism commensalism parasitism b. predator / prey relationships c. competition i. intraspecific competition ii. interspecific competition 2. population level interactions (Population Ecology) fluctuations in populations and genetic variation immigration and emigration isolation and evolution local extinctions Ecology: General Ecological Principles, Ziser, Lecture Notes,

5 3. community level interactions (Community Ecology) concept of the niche foraging theory community structure Kinds of Ecosystems each ecosystem is defined by a large set of converging conditions which will determine what species are found there the ecosystem itself is identified by a relatively few of these many characteristics: especially climate, soil, etc Under roughly the same sunlight, climate and soil conditions the same general plant communities tend to form Under the same general plant and climate conditions the same kinds of animals tend to congregate but within each ecosystem are numerous microhabitats Based on a few broad general characteristics ecologists divide the world into a few specific ecosystems or biomes as one moves along the earth s surface the environment changes gradually as various individual environmental factors change under a specific group of environmental conditions you find characteristic plant groupings and in these areas are found a characteristic group of animals often each identifiable biome has dominant species that characterize it within each biome is a distinctive combination of organisms that form a relatively stable community tied to specific environmental conditions but there is no distinct line of demarcation between vegetation types they merge into one another Major Factors Which Distinguish Ecosystems 1. Climatic Factors & Latitude and Altitude 2. Ecosystem Stability 3. Dominant Primary Producer 4. Dominant Consumers Ecology: General Ecological Principles, Ziser, Lecture Notes,

6 5. Species diversity, species richness, and biodiversity Major types of Ecosystems (=Biomes, FaunalRealms, Biogeographic Provinces) Terrestrial Ecosystems Freshwater Ecosystems Marine Ecosystems Ecology: General Ecological Principles, Ziser, Lecture Notes,