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Ecology

This article provides an overview of ecology, including the hierarchy of organization, basic scientific principles, major ecosystem processes, energy flow, nutrient cycling, and human impacts. It also discusses the carbon, nitrogen, and phosphorus cycles, as well as ecological principles and community dynamics.

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Ecology

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  1. Ecology What is it?

  2. 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

  3. Ecology Autecology: study interrelations of individuals with environment Synecology: study of communities

  4. 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

  5. Basic Scientific Principles • 2nd Law of Thermodynamics • When converting energy, always lose some energy as heat

  6. Major Ecosystem Processes • Energy Flow = energy moves through system 2) Nutrient Cycling = chemical elements recycled in system

  7. Energy Flow • Solar energy – primary energy source • (fig 3.5, p. 42) • Of incoming solar radiation: • 66% absorbed • 34% reflected (albedo)

  8. 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)

  9. 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)

  10. Energy Flow in Communities • food chain: sequence of organisms linked by energy & nutrient flow • trophic level: feeding level/position of organism in food chain

  11. 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

  12. Trophic Levels • Decomposers: (detritus feeder) consume and convert dead material for use by producers

  13. Food Webs • food web: interconnected food chains; all trophic interactions in community

  14. Human Impacts • Ecosystem simplification: elimination of species from food webs via human alterations to land • Example: vertebrate communities in ag. landscapes

  15. 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 = energypyramid

  16. Energy Flow Between Trophic Levels • Why such low efficiency? • Three Reasons: • 1) Escape behavior/protective coloration/unavailable material • 2) Indigestible material • 3) Cellular respiration

  17. Bioaccumulation = Biomagnification

  18. 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)

  19. Carbon Cycle • Carbon = building block of life • Reservoirs = atmosphere, ocean, organisms • High rate of exchange in/out reserves • Any relation to global warming?

  20. Nitrogen Fixation • Types • 1) atmosphericfixation via lightening or sunlight; NO3 as precipitation (ppt) • 2) biologicalfixation* via soil & water bacteria (blue-green algae); NH3; legumes & root nodules • Water Quality & Nitrates • Soil Condition & Fertilizers

  21. Phosphorus Cycle • Water Quality & Phosphorus • Eutrophication: increase in nutrient content of lakes

  22. 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

  23. 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

  24. 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

  25. 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

  26. 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

  27. What Happens in a Community? Types of Competition B) Intraspecific: competition within the same species, e.g., 2 oryx bobcats compete for space

  28. 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

  29. 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

  30. What Happens in a Community? (cont.) 2) Predation: one species consumes another species

  31. Some Ecological Principles • Community • Biological Succession: temporal sequence of one community replacing another; predictable • Primary vs. Secondary

  32. 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.

  33. 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

  34. 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

  35. Tropical Rainforests • Little temperature variation between months • Organisms add vertical dimension • Harbor staple foods and medicines for world’s human populations - increasingly exploited

  36. Tropical Dry Forest • Climate more seasonal than tropical rainforest • Heavily settled by humans with extensive clearing for agriculture

  37. Tropical Savanna • Climate alternates wet / dry seasons • Fire dependent

  38. Desert ~ 20% of earth’s land surface • Water loss usually exceeds precipitation • Human intrusion increasing

  39. 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

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