[B] General Biology
[B] General Biology Biol 102
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This 3 page Class Notes was uploaded by Marge Schiller on Thursday September 17, 2015. The Class Notes belongs to Biol 102 at Washington State University taught by Paul Verrell in Fall. Since its upload, it has received 9 views. For similar materials see /class/205994/biol-102-washington-state-university in Biology at Washington State University.
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Date Created: 09/17/15
NOVEMBER 18 amp 20 HUMAN POPULATIONS For most of human history there have been fewer than one billion people on the planet It was in the 1800s that our numbers started to climb Our global population is predicted to increase from around 6 billion in 2000 to around 9 billion ish in 2050 Reproductive decisions regarding fertility that are made by individuals when multiplied across all of the 39 J39 39J 39 present L vi 4 l affect r r 39 quot size and growth 10 Female determinants of fertility include the timing of puberty use of birth control with the global gag rule now lifted lowered fertility while breastfeeding and the impact of education Of course we mustn t forget about males Availability of information and appropriate technology is crucial for both sexes to make good reproductive choices and the responsibility of men in this regard is without question That said my focus on females isn t because I m a sexist It is because quite literally women have the babies that contribute to population size Population pyramids are diagrams that provide summaries of current population sizes and serve as predictors of the potential for future population growth The demographic transition model goes some way to explaining variation among nations The core idea is that as a nation moves toward a more developed economy a decline in death rate occurs before a decline in birth rate Thus there is the potential for a surge in population growth The greatest potential for global population growth is in developing nations many but not all of which are hotspots of biodiversity How many people can the planet support What is the Earth s carrying capacity for humans An ecological footprint measures the average per capita amount of land needed to provide people with the goods and services they need or want and enable wastes to be disposed of But does a nation s ecological footprint match its ecological capacity Does the world s NOVEMBER 30 BIODIVERSITY Biodiversity has a long and rather clumsy definition For us it is most easily defined in terms of a hierarchy of components diversity of genes of species of communitiesecosystems desert versus Arctic for example and of ecological processes such as predators and prey Species numbers often are used as an index of an area s biodiversity However biologists use several methods to determine whether two populations belong to the same species and results aren t always consistent A few more than about 15 million species have been described with perhaps 10 million lurking out there in total On land species numbers are greatest in the Tropics many of these tropical species are endemics with geographic distributions that are naturally restricted If an endemic vanishes from its naturallyrestricted home then it s gone from everywhere Why should we care about biodiversity Maybe you feel an ethical responsibility to the organisms with which we share the Earth Or perhaps you care because you nd biodiversity beautiful Or maybe you are more utilitarian Perhaps you value the goods and services that biodiversity provides such as pollination of crops by bees little penises with wings DECEMBER 2 7 9 POLLUTION PESTICIDES amp CHEMICAL SAFETY What is a pollutant One class of pollutant is something that is present in area where it should be absent Other pollutants may occur naturally but human activity then boosts them to abnormally high levels Pollution is a global problem across all kinds of habitats 7 pollutants travel Pollutants may come from either point or nonpoint sources The latter are the hardest to monitor and regulate Pests have been a problem ever since agriculture was developed around 10000 years ago For years we have waged war against pests with chemicals designed to kill them But not all of these chemicals are specific to their intended targets Contamination of nontarget species 7 Rachel Carson and the story of DDT By eating contaminated prey with DDT stored in fatty tissues DDT became bioconcentrated or bioaccumulated in predators at higher levels in food webs At the top of the food web populations of predatory birds started to decline Why Because DDT caused egg shells to thin and few live baby birds to hatch Today in the US the use of DDT is very restricted because of effects in nontarget species Because of nontarget contamination and the evolution of pesticide resistance our strategy today is one of Integrated Pest Management IPM rather than Outright Pest Eradication OPE 7 careful use of chemicals use of natural enemies and use of bioengineered crops How do we test whether a chemical is safe This is a difficult job for the Environmental Protection Agency Let s design a test What decisions will we have to make 1 1 Who should we test Mice Frogs People Should we expose our subjects to large amounts in short periods of time or to smaller amounts over longer periods What should we measure as an endpoint Something obvious like death the basis of an LD 50 or cancer Or something more subtle like problems with fertility A growing number of chemicals disturb the hormonal control of reproduction either by mimicking the effects of natural hormones or blocking their effects Such hormone disrupters have been shown to affect cells growing in dishes laboratory animals and wildlife But what about us The average woman in the US has a oneineight chance of developing breast cancer If a man lives long enough he will probably die with prostate cancer even if not from prostate cancer Is there a link with our use of chemicals Can we be certain How should we deal with uncertainty Should we just wait and see or should we use the Precautionary Principle The latter states that if the consequences of doing nothing might be sufficiently bad then maybe it is best to act now even if we aren t 100 certain whether those bad consequences will actually come about And shouldn t we apply this same principle to some of the incredible genetic and cellular advances that we discussed so many weeks ago Well shouldn t we
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