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Section 2.docx

by OneClass239967 , Fall 2013
38 Pages

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Indicators of Overpopulation?
Conflict for Resources
Making Your Case
Are your population numbers getting better or worse?
Most environmental problems not a result of growth rate, but number of actual individuals
What biological or social factors are associated with higher or lower birth rate?
Health Care, maternal
Children important in labor rate
Lower infant mortality rate
Economic growth
Education, employment
Pension Funds
Availablity of birth control
Increased cost of living
20th Century; population increased from 1.6 bill to 6 billion
Major events that exerted downward pressure
Death Rate
The other part of population growth
Overall might be bigger cause of pop growth than birth rate
Last 50 years
# of births has risen steadily
In some African countries, almost same as birth rate
South Africa, due to AIDS
What’s decreasing death rate, and raise life expectancy
Increased health technology
Better nutrition
Improved sanitation
Improved personal hygiene
Safer water supplies
Does Population increase really cause environmental problems?
Julian Simon-no
Technology can solve all problems
More people=more likely to be someone who can solve the next crisis
Everytime humans looks like we might hit a limit, we find a way around it
Keystone work “The Ultimate Resource” 1981:
Some arguments in Favor of “no”
Per capita income has steadily increases
Vehicles, raising at 4% a year, no environmental damage for years, cars aren’t a problem
Limitations in non-renewable resourcesmore efficient use and alternatives discovered
Assertion: most of the worst ecological problems have arisen in last 25 years
World population rate of growth 20 years ago was 2% and now 1.8%
Slow change is often unnoticed
Pumping small amounts of raw sewage into a river
Normal processes of the river can accommodate
But at some
Habitat loss and occupancy by species
Spotted salamander
Can be a plus or minus
Phosphate detergent use in US since WWII
From 1946 to 1968 phosphate use in detergents increased 20x but populations size only increased 1.5x
Phosphate is a limiting nutrient, limits aquatic NPP
Increase P input=algal blooms
Species Differ in Population Growth Rate Potential
Life Histories

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10/16/2013 Indicators of Overpopulation? Conflict for Resources Making Your Case Are your population numbers getting better or worse? However, Most environmental problems not a result of growth rate, but number of actual individuals What biological or social factors are associated with higher or lower birth rate? Higher Health Care, maternal Children important in labor rate Lower infant mortality rate Lower Economic growth Education, employment Urbanization Pension Funds Availablity of birth control Increased cost of living th 20  Century; population increased from 1.6 bill to 6 billion Major events that exerted downward pressure Death Rate The other part of population growth Overall might be bigger cause of pop growth than birth rate Last 50 years # of births has risen steadily In some African countries, almost same as birth rate South Africa, due to AIDS What’s decreasing death rate, and raise life expectancy Increased health technology Better nutrition Improved sanitation Improved personal hygiene Safer water supplies Does Population increase really cause environmental problems? Julian Simon­no Technology can solve all problems More people=more likely to be someone who can solve the next crisis Everytime humans looks like we might hit a limit, we find a way around it Keystone work “The Ultimate Resource” 1981:  Some arguments in Favor of “no” Per capita income has steadily increases Vehicles, raising at 4% a year, no environmental damage for years, cars aren’t a problem Limitations in non­renewable resources▯more efficient use and alternatives discovered Assertion: most of the worst ecological problems have arisen in last 25 years World population rate of growth 20 years ago was 2% and now 1.8% Problems Slow change is often unnoticed Non­linear—Threshold Pumping small amounts of raw sewage into a river Normal processes of the river can accommodate But at some  Habitat loss and occupancy by species Spotted salamander Technology Can be a plus or minus Phosphate detergent use in US since WWII From 1946 to 1968 phosphate use in detergents increased 20x but populations size only increased 1.5x Phosphate is a limiting nutrient, limits aquatic NPP Increase P input=algal blooms Species Differ in Population Growth Rate Potential Life Histories Assumption: resources are limited Therefore organisms must balance how they allocate time and resources to growth and reproduction Involves tradeoffs Maturity (age of first reproduction) Parity (number of episodes of reproduction) Fecundity (number of offspring/episode of reproduction) What are some implications for humans? Weeds Fisheries Farming Tradeoffs Competitors▯ increasing resources and stability Ruderals▯increasing disturbance Stress tolerators▯ increasing stress Implications for Farming Disturbance environment Fisheries 10/16/2013 Plague Video Clip Epidemics The same black plague that devasted Europe is back Her cat became ill from a dead squirrel, thereby infecting the woman The plague began in China, and from there dispersed around the world such as Cali and Italy Transferred from fleas Once the flea attaches to a rodent and kills them, they have to look for a new source, sometimes a human The way we live influences plagues If we don’t monitor, there might be another breakout Key Factors behind Disease Outbreaks Key factors Human behavior Bacterial Disease Evolution Due to excessive antibiotic use Prescriptions, given when not needed Domestic animals 50% of antibiotics used in US is transferred to animals Sexual behavior, drug use, travel Resisting vaccinations Vaccine coverage needs to be at 90­95% for herd immunity 10/16/2013 Immunity of a sufficient number of individuals in a population results that one will not result in a breakout Some people and communities refuse to get vaccinations Changing Ecological Conditions Ex: water (irrigation, dams, small impoundments of water) EX: Aswan High Dam in Egypt Who benefits? Pros 1/3 of Egypt’s electricity fewer droughts increased food production flood control in the lower Nile basin cons Schistosomiasis 650 million cases per year high mortality in children specific riparian snails that are reservoirs snail diversity reduces infection prevalence of Schistosomiasis ex: land use changes/urbanization e.g. Deforestation/fragmentation e.g. Lyme Disease and the Black­Legged tick Myths It’s the deer (BUT not correlated with deer abundance) It’s the mice (BUT shrews, chipmunks and some birds are also key reservoirs of Lyme Disease Hypothesis 1: Dilution Effect Low diversity communities tend to favor disease transmission They contain best hosts Very resilient to disturbance/diversity loss High competence Hypothesis 2: Changes in the Food Web! What determines mammal diversity Urbanization changes the food web 10/16/2013 EX: Lyme Disease in NE Mouse food: seeds, acorns Mouse predators: hawks, owls, weasels 10/16/2013 Why is the world green? Plants cant move or hide Herbivores obtain their energy from plants Nitrogren is often limiting Leaf tissue: 2­6% Animal tissue: >10% nitrogen (=herbivores have to eat and concentrate nitrogen to grow) Why don’t herbivores eat all/most of the leaves in the world? Hypothesis? Observation: The world is green. Why? H1­because herbivores don’t want to eat all their resources (they are good stewards) H2­because predators kill all the herbivores before they can eat all the leaves H3­because herbivores are limited by some other resource Also a problem for animals, don’t want to get eaten either Co­evolutionary Arms Race=positive feedback cycle Predator eats prey, prey evolves and gains new defense Predator can’t eat new prey, so they come up with a new counter defense, become a new predator and eat  the new prey Positive feedback cycles sped up processes Diversity leads to Diversity In species and in traits Defense traits Behavioral 10/16/2013 Morphological Mimicry Chemical Chemical mediation of interspecific interactions Host nutritional quality (plant or animal) Host chemical defenses Primary vs Secondary Metabolites Metabolite=a chemical produced by an organism metabolically (alternative=sequestered from diet) Primary metabolites Metabolites essential for growth and reproduction Carbs Essential amino acids We don’t care about them Secondary Metabolites Not essential for growth and reproduction Functions: Resistance to abiotic environment Resistance to biotic environment Taste bad=don’t get eaten 10/16/2013 4/5 of all secondary metabolitcs have been found in plants (relatively few in animals & most of those were  derived from plants) Note: Recent explosion of research in microbiology has led to discovery of many more in microbes In the news Rare plant has chemicals that combat hepatitis C and diabetes Plants are at risk: Habitat loss, invasive species, climate change driving many plants toward extinction Many organisms produce toxins that affect their enemies. They may repel, sicken, or kill (remember:  humans are often enemies too) Chemicals as Medication ½ of prescribed medicines come from natural sources Models for new drugs Chemical templates Plant­based Medicines Quinine of Cinchona trees Bark of Cinchona trees has long been used by indigenous peoples of the Amazon to control fever.  Aspirin derived from salicylic acid of willow bark For treatment of fever, pain, inflammation Vincristine and Vinblastine from Rosy Periwinkle Alkaloids that can fight cancer, especially leukemia and Hodgkin’s disease Taxol from Pacific yew trees Challenge: How can society produce enough to fight malaria globally? 10/16/2013 Toxin Effects on Humans Ricin is an alkaloid  If plants contain so many noxious chemicals, why do we have pest outbreaks in agriculture? Some answers Animals with Medicinal Value Leeches Produces an anti­coagulant, helps stop excessive bleeding People are not just people Microbes: a little tapped resource 1000 species of bacteria from 19 phyla just on human skin 10^14 microbes per human may help you­probiotics after antibiotics most microbes cannot be cultured­makes them difficult to study an Ant­microbe mutualism leaf cutter ants­some species actively cultivate fungus 10/16/2013 Fungal Associates Good=Basidiomycete Bad=escovopsis Solution: another mutualist, Streptomyces, a bacteria that only affects escovopsis Chemical Prospecting Where would you look for bioactive chemicals? Some thoughts Secondary metabolites are everywhere and found ine very kingdom The next discovery may be from a plant Process of Natural Product drug discovery in the US Acquisition Discovery Screening strategies (random, targeted, rational) Screening (confirmation, specificity, mechanisms) Chemical Isolation and ID (bioactivity­based isolation) Pre­clinical Development Generate supplies (raw material) Animal Studies I (activity and simple toxicity) Large­scale production Clinical Development Clinical trials Safety and efficacy Efficacy relative to established treatments New drug application to US Food and Drug Administration Herbal Medicines A: Randomized and double blind experiments Randomized=subjects randomly placed in treatment group (control, treatmens) 10/16/2013 Gene to Combat Wheat Rust Discovered 10/16/2013 USDA scientists found a molecu From the Andes to Europe Potatoes originated from Andes region, 1500s brought over to Europe via US Early 1800s Ireland prospering because of potatoes Started supporting England during wartime 1845 Disease broke out in potato plants Potato Blight From east coast of North America, earl 1840s Within months, blight spread, destroying Ireland’s staple crop As harvests across Europe failed, price of food rises Potatoes=food; rotted in cellars Economic ruin for many Eat rotten potatoes▯sick; villages consumes with cholera and thypus 1846 Universal crop failure Raised unemployment 10/16/2013 1847 Worst of famine Typhus and dysentery widespread 100,000 emigrated to US Results of Potato Blight Economic Justice 1­2 million dead from hunger, disease 1­2 million emigrated Why was the potato so vulnerable? England had plenty of food, didn’t give any to Ireland Genetics and Human Behavior Little genetic variability Everyone used same variety Isogenic=no genetic variation Top cereals globally 1. Corn 2. Wheat 3. Rice Food Insecurity 10/16/2013 Will wheat produce a new global famine? Moving Forward: How will we feed the every increasing population of people? Does food production depend on biodiversity 12 plants­75% of food supply 15 mammals/birds­90% of livestock production Selective Breeding Domestication of Plants and Animals Central to human societal development Breeding wild plants and animals into a “tame”, modified version Selection for traits Corn (Zea mays) Mesoamerica Domestication of corn=sedentary lifestyle Accidental plant breeding by artificial selection 1. Genetic variation  Slowly larger 2. Heritability 10/16/2013 Much larger 3. Increased survival (selective harvest) For example, did you know? 8000 varieties of apples grew in US in 1900s. More than 95% no longer exist In Mexico, only 20% of corn varieties recorded in 1930 can now be found In China, only 10% of the 10,000 wheat varieties now exist 400,00 plant species, 150 of these are cultivated, and 12 provide 75% of global food Did you know? The Holstein cow represents 91% of the nation’s dairy stock 50% of US breeds of swine lost in last 50 yeas, most other are n danger of extinction Only several strains of large white turkey represent more than 90% of all turkey production Traditional approaches 1. Selectively breed individuals with extreme traits large seed size, high productivity 2. Interbreed varieties to mix and match traits cross large apples with little flavor with small, sweet variety to get large, sweet apples broccoflower 10/16/2013 Crops­goal of specialization Different environmental conditions everywhere=different types grow better in different places Different varieties have different traits Drought resistant, but grow slow in wet years Faster grower, but particular rain needs High protein, resistant to insect pests Goal=get best mix of genes, for a particular place, into a single variety Green Revolution e.g. miracle Rice, 1966 Short stalk (resist windfall) Very sensitive to fertilizer (grow more with less) Few photoperiodic requirements (=fits any day length) No temperature requirements Very fast maturation=2­3 crop rotations/year Some problems with many new crops 1. New strains of wheat and rice require 2­3x fertilizer and pesticides 2. Economic limitations ex: more yield might require mechanical cultiv
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