Transcript Document
What is it? Ecology Ecology • Hierarchy of Organization - Individual - Population - # of individuals in given area - Community – all biota in an area - Ecosystem – all biota & abiotic factors - Landscape – multiple ecosystems over large area - Biosphere – all life on Earth Ecology Autecology: study interrelations of individuals with environment Synecology: study of communities Basic Scientific Principles • Law of Conservation of Matter Matter cannot be created nor destroyed, rather it can only be transformed • 1st Law of Thermodynamics (Energy) Energy cannot be created nor destroyed, rather it can only be converted in form Basic Scientific Principles • 2nd Law of Thermodynamics When converting energy, always lose some energy as heat Major Ecosystem Processes 1) Energy Flow = energy moves through system 2) Nutrient Cycling = chemical elements recycled in system Energy Flow • Solar energy – primary energy source (fig 3.5, p. 42) Of incoming solar radiation: 66% absorbed 34% reflected (albedo) Solar Energy • Of solar radiation absorbed: - ~22% water cycle - nearly all transform to heat & radiates emissivity: relative ability of Earth to release energy (e.g., radiate heat into space; link to global warming) Solar Energy • Tiny amount of solar energy into photosynthesis (< 0.1%) photosynthesis (PNS): use solar energy to convert CO2 & H2O into sugar; by-product = O2 primary production: all organic matter resulting from PNS; raw material for other organisms (gross production vs. net production) Energy Flow in Communities food chain: sequence of organisms linked by energy & nutrient flow trophic level: feeding level/position of organism in food chain Trophic Levels Producer: (autotrophs) anchor of chain; produce all organic matter for other organisms Heterotrophs (consumers) Primary consumer: directly consume producers = herbivores Secondary consumer: consume herbivores Tertiary & Quaternary consumers: consume secondary & tertiary consumers, respectively Trophic Levels Decomposers: (detritus feeder) consume and convert dead material for use by producers Food Webs food web: interconnected food chains; all trophic interactions in community Human Impacts Ecosystem simplification: elimination of species from food webs via human alterations to land Example: vertebrate communities in ag. landscapes Energy Flow Between Trophic Levels Does 100% of energy transfer from 1 trophic level to another? No. Remember 2nd Law of Thermodyn. Range 5-20% transference (usually ~10%) Graphical representation of energy transference in food web = energy pyramid Energy Flow Between Trophic Levels Why such low efficiency? Three Reasons: 1) Escape behavior/protective coloration/unavailable material 2) Indigestible material 3) Cellular respiration Bioaccumulation = Biomagnification Nutrient Cycles What does the Law of Conservation of Matter state? • circular flow of chemicals = recycling • Inputs & relationship to energy flow? • Water, Carbon (C), Nitrogen (N), Phosphorus (P), Sulfur (S) Carbon Cycle • Carbon = building block of life • Reservoirs = atmosphere, ocean, organisms • High rate of exchange in/out reserves • Any relation to global warming? Nitrogen Fixation Types 1) atmospheric fixation via lightening or sunlight; NO3 as precipitation (ppt) 2) biological fixation* via soil & water bacteria (blue-green algae); NH3; legumes & root nodules Water Quality & Nitrates Soil Condition & Fertilizers Phosphorus Cycle • Water Quality & Phosphorus • Eutrophication: increase in nutrient content of lakes Some Ecological Principles Individual • Law of Tolerance: organisms can tolerate a range of conditions beyond which they die • e.g., temperature, nutrients • age-dependent, DNA Where does habitat fit? Habitat: home; area having necessary resources (food, water, cover) and environmental conditions (temp., ppt) that allows organism to live & reproduce Your habitat = ????? What if habitat is drastically changed or destroyed? • Move, Adapt, or Die Properties of Communities 1) Species Richness = # species in a comm. 2) Species Evenness = relative abundance of different species 3) Species Diversity = richness & evenness e.g., Four species (A,B,C,D) in 2 different communities Comm 1 – 25A 25B 25C 25D Comm 2 – 97A 1B 1C 1D What Happens in a Community? 1) Competition: individuals contest over a resource (food, space, water, mates…) – major factor determining structure http://fr.truveo.com/The-Raccoon-and-Two-House-Pets/id/2429116624 What Happens in a Community? Types of Competition A) Interspecific: competition between different species, e.g., blue jay & chickadee compete for sunflower seed at feeder What Happens in a Community? Types of Competition B) Intraspecific: competition within the same species, e.g., 2 oryx bobcats compete for space Principle of Competitive Exclusion (Gause’s experiments) • Two species which compete for same resource cannot coexist in same place at same time • Implications = different locations or different times • Relates directly to niche concept Niche Concept Niche: functional role (“occupation”) & position (spatial & temporal) of a species in its community • Principle of Competitive Exclusion = 2 species cannot occupy the same niche What Happens in a Community? (cont.) 2) Predation: one species consumes another species Some Ecological Principles Community • Biological Succession: temporal sequence of one community replacing another; predictable • Primary vs. Secondary Terrestrial Biomes • Biomes - distinguished primarily by their predominant plants and associated with particular climates. – Geographic and seasonal variations in temperature and precipitation are fundamental components. • Soil : Foundation of Terrestrial Biomes Soil is a complex mixture of living and non-living material. – Classification based on vertical layering (soil horizons) • Soil Profile = snapshot of soil structure in a constant state of flux Soil Horizons • O horizon: Organic Layer freshly fallen organic material - most superficial layer • A horizon: Mixture of minerals, clay, silt and sand • B horizon: Clay, humus, and other materials leached from A horizon - often contains plant roots • C horizon: Weathered parent material Tropical Rainforests • Little temperature variation between months • Organisms add vertical dimension • Harbor staple foods and medicines for world’s human populations - increasingly exploited Tropical Dry Forest • Climate more seasonal than tropical rainforest • Heavily settled by humans with extensive clearing for agriculture Tropical Savanna • Climate alternates wet / dry seasons – Fire dependent Desert ~ 20% of earth’s land surface • Water loss usually exceeds precipitation • Human intrusion increasing Mediterranean Woodland & Shrubland (Chaparral) • All continents except Antarctica • Climate cool & moist in fall, winter, and spring; hot & dry in summer • Fire-resistant plants due to fire regime Temperate Grassland • Periodic droughts • Soils tend extremely nutrient rich and deep • Dominated by herbaceous vegetation • Warm season grasses (tall grass vs. short grass) • Large roaming ungulates – Bison vs. cattle Temperate Forest • Fertile soils – Long growing seasons dominated by deciduous plants – Short growing seasons dominated by conifers • Many major human population centers Boreal Forest (Taiga) • Northern Hemisphere – ~ 11% of earth’s land area • Thin, acidic soils low in fertility • Generally dominated by evergreen conifers • Historically, low levels of human intrusion • Covers most of lands north of Arctic Circle – Climate typically cool & dry; short summers • Low decomposition rates • Human intrusion historically low, but increasing as resources become scarce – What type of increased use? Tundra dN rN dt dN N rN 1 dt K Density-dependent Effects Who Cares? Why bother discussing these models? Metapopulations & Source-sink Populatons highlight the importance of: • habitat & landscape fragmentation • connectivity between isolated populations • genetic diversity Habitat Fragmentation • Process of breaking contiguous unit into smaller pieces; area & distance components • Leads to: < remnant patch size > edge:interior ratios > patch isolation < connectivity • Community & Ecosystem processes altered Habitat Fragmentation • First-Order Effects: fragmentation leads to change in a species’ abundance and/or distribution • Higher-Order Effects: fragmentation indirectly leads to change in a species abundance and/or distribution via altered species interactions Habitat Fragmentation • area-sensitive species: species that require minimum patch size for daily life requirements • Edge effects: influence of factors from outside of a patch Edge Effects • Habitat surrounding a patch can: - change abiotic conditions; e.g., temp. - change biotic interactions, e.g., predation Example of nest predation = edge effect of approximately 50 m into forest patch Conservation Implications • All habitats are “islands” • The “internal external threat” • Develop & manage reserve as landscapes/ecosystems linked by movement of species (metapop. concepts) • Develop strategies for countering edge effects……predator control?????