BIOL 1005 1st Edition Lecture 17 Outline of Last Lecture I. WeatheringII. Soil FormationIII. Other Factors Influencing Soil FormationIV. Soil PropertiesV. Soil ProfileVI. Soil HorizonsVII. VideoOutline of Current Lecture I. Soil ProfilesII. Soil ErosionIII. CostsIV. U.S.V. GlobalVI. Soil Conservation PracticeVII. Conventional vs. Conservation TillageVIII. Problem IX. Biodiversity and the Species ConceptX. What are Species?XI. How Many Species are there?XII. Benefits of BiodiversityXIII. Threats of BiodiversityThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.XIV. Natural Causes of ExtinctionXV. Human Caused Reductions in BiodiversityXVI. Endangered Species Management XVII. Endangered Species ActXVIII. Captive BreedingCurrent LectureI. Soil Profiles- Mixtures - Over 15,000 separate soil types have been classified in North America. - Grassland Soils—Usually have a deep A Horizon—Low rainfall limits topsoil leaching. A Horizon supports most root growth.- Forest Soils—Topsoil layer is relatively thin, but topsoil leachate forms a subsoil that supports substantial root growth.II. Soil Erosion- Erosion—Wearing away and transportation of soil by wind, water, or ice.- Worldwide removes 25.4 billion tons/yr.- deforestation and desertification.- agricultural practices.- Average annual erosion rate in the U.S.- Cultivated cropland – 3.5- 5 tons/acre/year- Rangeland – 1.5 – 1.7 tons/acre/year- Forestland – 1 ton/acre/year- Mississippi River moves 325,000,000 mTons/year III. Costs- most productive layers (A horizons) lost first- farmers must add more fertilizers- streams’ bottoms become covered with silt, destroying much habitat- sediments must be dredged if in shipping lanesIV. U.S.- In U.S., about 50% of lands are capable of raising crops (21% currently, 26% in pasture).- Only 2% of lands are not susceptible to excessive erosion.V. Global- Worldwide, only 35% of lands are capable of raising crops (11% currently, 24% in pasture).VI. Soil Conservation Practices- Contour Farming—Tilling at right angles to the slope of the land. Each ridge acts as a small dam.- Strip Farming—Alternating strips of closely sown crops to slow water flow.- Terracing—Level areas constructed at right angles to the slope to retain water.- Good for very steep land.- Waterways—Depressions in sloping land where water collects and flows off the land.- Windbreaks—Planting of trees or other plants that protect bare soil from full force of the wind.VII. Conventional vs Conservational Practices- Plowing has multiple desirable effects:- Weeds and weed seeds are buried or destroyed.- Crop residue is turned under.- Decays faster and builds soil structure.- Leached nutrients brought to surface.- Cooler, darker soil brought to top and warmed.VIII. Problem- Each trip over the field is an added expense to the farmer, and at the same time increases the amount of time the soil is open to erosion via wind or water.- Reduced Tillage— Uses less cultivation to control weeds and prepare soil, but generally leaves 15-30% of soil surface covered with crop residue after planting.- Conservation Tillage—Further reduce amount of disturbance and leaves 30% or more of soil surface covered with crop residue.- Mulch Tillage—Tilling entire surface just prior to planting.- Strip Tillage—Tilling narrow strips.- Ridge Tillage—Leave ridge.- No Till—Place seeds in slits.IX. Biodiversity and the Species Concept- What is Biodiversity ?- Genetic Diversity - Measures variety of different versions of same genes.- Species Diversity - Measures number of different kinds of organisms within a community.- Ecological Diversity - Measures richness and complexity of a community.X. What are Species?- Species Definition- Reproductive Isolation- Genetic Species Concept- DNA sequencing- Evolutionary Species Concept- More genetic diversity is better and more stable- Ecological diversity – how different those communities areXI. How Many Species are there?- Currently 1.7 million species identified.- Estimates range between 3-50 million.- May be 30 million insect species.- Invertebrates make up 70%- Tropical rainforests and coral reefs are biodiversity hotspots.XII. Benefits of Biodiversity- Food- As many as 80,000 edible wild plant species could be utilized by humans.- Drugs and Medicines- More than half of all prescriptions contain some natural product.- Pharmaceutical companies actively prospect tropical countries for products.- Ecological Benefitso Soil formation, waste disposal, air and water purification, nutrient cycling,solar energy absorption, and biogeochemical and hydrological cycles all depend on biodiversity.o Can a system function without all its integral parts ?- Aesthetic and Cultural Benefitso Cultural diversity inextricably linked to biodiversity.o USFWS estimates Americans spend $104 billion annually on wildlife-related recreation.o Ecotourism can be an important form of sustainable economic development.o Existence (intrinsic) value.o Aesthetics – how appealing it is to your eyesXIII. Threats to Biodiversity- Extinction - Elimination of a species.- Natural Causes- In undisturbed ecosystems, background rate appears to be one species per decade.- In this century, human impacts have accelerated that rate, causing perhaps hundreds to thousands of extinctions annually.XIV. Natural Causes of Extinction- Fossil record suggests more than 99% of all species ever in existence are now extinct.- Most went extinct before humans arrived.- End of Cretaceous - Dinosaurs and 50% of existing genera disappeared.- Permian period - Two-thirds of all marine species and nearly half of all plant and animal families died out.XV. Human Caused Reductions in Biodiversity- Habitat Destructiono Biggest reason for current increase in extinction is habitat loss. Habitat fragmentation divides populations into isolated groups vulnerable to catastrophic events.- Northern Spotted Owl- Invasive Species- Invasive (exotic) organisms thrive in new territory where they are free of usual predators, diseases, or resource limitations that limited them in original habitat.o Over past 300 years, approximately 50,000 non-native species have become established in the U.S.. At least 4,500 are free-living.- 15% cause environmental damage.- Pollutiono Pesticideso Lead- Populationo Human population growth Resource Use- Overharvestingo American