Week of Notes 11/30-12/4
Week of Notes 11/30-12/4 BSC 116
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This 7 page Class Notes was uploaded by Rani Vance on Saturday December 5, 2015. The Class Notes belongs to BSC 116 at University of Alabama - Tuscaloosa taught by a professor in Fall 2015. Since its upload, it has received 9 views. For similar materials see Principles Biology II in Biological Sciences at University of Alabama - Tuscaloosa.
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Date Created: 12/05/15
BSC 11/30-12/4 Lecture 41: Biodiversity Higher extinction rates now than ever before, mainly caused by human activity There are multiple threats to biodiversity 1. Habitat loss and destruction: -biggest threat to biodiversity -caused 73% of known extinctions -fragmentation of habitats fragments populations (picture in slideshow demonstrates this, habitat split up, patchwork landscape) -high levels of biodiversity in Alabama, but also subject to the most threats 2. Introduced/Exotic Species -increase in global travel led to increase in introduced species -non-native species alter ecosystems -some introduced by accident: stowaways (brown tree snake Guam: 12 birds, 6 lizards extinct) -some introduced on purpose ie, kudzu introduced to stabilize sediments (taken over the south) ie, various insects introduced as biological controls (predators, etc.) ie, San Francisco Bay establishes a new invasive sp. ever 14 weeks, arrive via shipping 3. Overexploitation -esp. fisheries and large mammals -harvested at rates faster than they can reproduce -ie, hunting of elephants, rhinos, and whales 4. Global change -Change in climate and atmospheric chemistry -Climate change -Acid rain Human activity cause habitat destruction -Agriculture: primary cause of ecosystem change **slash and burn agriculture -Natural Resource Extraction (mining, logging, fishing) -Urbanization and infrastructure developmenthabitat fragmentation -War and violent conflict -Pollution Pollution toxins accumulate in top predators humans add lots of synthetic chemicals to ecosystems – ie, pesticides, industrial chemicals like PCBs (polychlorinated biphenyls) – not broken down by detritivores (decomposers) **taken up by primary consumers – **move up the food web! – biological magnification: becomes more concentrated in higher trophic levels ie, DDT (insecticide) used in USA from 1950s to 1970s (now band in USA) – accumulated in birds of prey, like bald eagles – leads to weak egg shells (birds would sit on and break eggs, no longer viable) – still use DDT in Africa where malaria (spread by mosquitoes) a serious human health issue; trade-offs also release naturally-occurring chemicals at unnatural levels – ie, mercury from plastic manufacture, coal burning – **taken up by phytoplankton moves up the food chain – accumulates in predators, especially fishes mitigated by regulating wastes, but may take decades to degrade Invasive species: Invasive species: An introduced species that establishes, expands its range, and has a substantial impact on native organisms & ecosystems - fire ants have become devastatingly invasive - introduced to USA in Alabama from a ship in Mobile from South Amercia Invasive species can interact with native species: -as competitors, prey, predators -brown tree snakes outages in Guam due to snakes on powerlines Overexploitation: -hunting (chose largest animal to make the most money) -fishing -fisheries by catch (not much incentive for fishermen to catch in a sustainable manner) -**this has an effect on non-harvested species as well (can be caught by accident) -this is called “bi-catch” -collecting for trade -can lead to a decrease in species abundance and ultimately extinction of the species. Burning fossil fuels leads to acid rain burning fossil fuels (oil, coal) releases S and N – combines with water to make sulfuric and nitric acids – leads to acid rain: pH < 5.2 – lowers pH of water bodies in areas with weakly buffered water (less bicarbonate to neutralize it) lower pH kills acid-sensitive fishes – ie, lake trout: keystone predators; drastically alters ecosystems source of pollution distant from the effects – e.g., 1960s factories Midwest killed lakes in eastern Canada – can be (has been) mitigated thru tougher regulations on emissions: still takes a long time to recover Chemicals we release can also affect abiotic factors CFCs (chlorofluorocarbons) used in refrigeration, air conditioners – escape to atmosphere, Cl reacts with ozone (O )317-25 km up – ozone breaks down to O 2 the layer of ozone in the atmosphere absorbs UV radiation – less ozone means less UV protection – ****increase in DNA mutation rate in organismscancer results in a large “hole” in the ozone, esp. over Antarctica (and Australia, New Zealand, South America) – less of an effect at middle latitudes increased UV radiation leads to DNA damage in plants and animals – predicted to result in increased skin cancers, lower crop & natural productivity Excess CO2 in atmosphere from burning fossil fuels associated with increasing global temps before the Industrial Revolution, [CO ] = 274 ppm 2 – now, it is over 380 ppm – this is highly correlated with increased global temperatures CO 2 CH ,4H 2, etc. naturally warm the Earth thru Greenhouse Effect – greenhouse gases have the same effect • solar heat retained the global warming trend on Earth has had greatest effect at high latitudes INCREASE GREEN HOUSE GAS LEADS TO INCREASE IN TEMP – less polar ice means more absorption of heat (exacerbates warming) – increase in the incidence of fires (exacerbates CO increase) 2 – predicted to lead to: changes in precipitation patterns: aridification in some place, more water in others increase in sea level from melting polar ice extinctions as organisms can’t adapt to rapid change Lecture 42 Global Human Population Size: positive growth but no longer exponential **logistic and exponential population growth, must know for test -levels off to carrying capacity Annual percent increase in global human population size (no longer exponential) Human population growth and age structure varies by country depending on whether they are industrialized or developing Population growth and age structure varies by country depending on whether they are industrialized or developing -demographic transition: switch from high birth and death rates to low birth and death rates in a given country, tends to accompany industrialization and improved living conditions -these graphs are based on the type of development each country has gone though -ie high death rate with equally high birth rates are seen in developing country -ie in developed countries, there is a relatively even slow population growth, that tapers **WE DON’T KNOW WHAT THE CARRYING CAPACITY OF THE EARTH IS.. -static? Or changing? Ecological footprint measures human impact -calculates how much land and water resources we consume to grow food, support lifestyles, and assimilate waste, can also be measured as energy consumption -can be used to show changes in impact through time and space Goal for conservation biology is to conserve biodiversity biodiversity = biological diversity -anthropogenic (human caused) ecosystem modification higher extinction rates – always some extinction, but more species going recently Why worry about conserving biodiversity? – we have an innate tie to nature: biophilia – we have an obligation to future generations – we are still discovering useful things we can get from species – provide us with useful services: ecosystem services e.g., clean, detoxify waste, pollinate crops provide services that would cost $$ – those species that we rely on are in communities with other species Concerned with biodiversity lost on multiple levels most often hear about extinction of species – in U.S. extinction of freshwater animals 5x greater than terrestrial – preservation of species needed for genetic diversity – within & among pop. variation: necessary for future adaption to changing environment – Loss of genetic diversity reduces adaptive potential of the species – community and ecosystem diversity: fates of species interconnected – protect habitats, protect species Multiple threats to biodiversity 1. Habitat destruction (greatest threat) 2. Introduced/exotic species 3. Overexploitation 4. Global change Lecture 43: Conservation and Restoration Ecology Efforts to protect species revolve around keeping their numbers from getting too low -a species becomes endangered when its population gets too small – extinction vortex: small populations lead to smaller populations which leads to extinction – small population varies among taxa – want them to be large enough to sustain themselves – minimum viable population (MVP) size: number of individuals at which a species is able to sustain its numbers and not enter the extinction vortex – MVP depends on the species – uses effective population size (number in pop. that breed), demographic modeling to predict how long a pop. can last • e.g., grizzly bears in Yellowstone, 125/500 breeding; 95% chance pop. will last 200 yrs Focus on landscapes and habitats instead of species -by protecting land we are able to help multiple species – set aside large tracts of land to protect against fragmentation edges: boundaries between communities or ecosystems edge effects increase due to habitat fragmentation corridors: strips of habitat that connect otherwise isolated habitat fragments, facilitates movement and dispersal can focus on biodiversity hot spots: smaller areas with lots of diversity – 1.5% of land on Earth has >30% off all plant & animal diversity – but, what’s a hot spot for one taxon, might not be for another used to set aside land to keep it pristine – based on old stability, “balance-of-nature” thinking Yellowstone, old policy of putting out fires -disturbing marine ecosystems, just as if not more important than terrestrial ecosystem -negative stimulus spreads more easily in water etc Restoration ecology occurs when ecosystems are too far degraded -extremely damaged ecosystems may need repair before they can be restored ie: turning open-pit mine to salt marsh takes bulldozers -bioremediation: using plants, fungi, prokaryotes, etc. to detoxify an area in contaminated areas, plant that can take up the contaminants; then harvest the plants or with bacteria to remove the contaminants - biological augmentation: use organisms to add compounds to ecosystem -ie: legumes increase N in soils until native plants can thrive