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Studying for a test? Prepare with these 2 lessons on Crash Course: Biology and Ecology.
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I think we should do this one outside. This is better. This is beautiful. It's just , of course, except for this. Liter, it's a kind of pollution but like barely. I'd rather it not be here. It makes me kind of angry, and it makes nature less pretty. Environmentally, there's a pretty low chance that this can or even a million more like it is going to have a significant negative impact on an Eco system. The kind of pollution we really have to worry about is the kind we don't see. Either because it's invisible or because it's being done in places that are way out the way that we're less likely to encounter. That's by design, of course, because when people actually see the impact that their lifestyle can have on the world, they tend to somethings change the way that they live. Also, they way that they buy. We can't have that, so, it's time to get our hands dirty. (upbeat music) Pollution is, kind of catch all term, for any substance that's in the wrong place or in the wrong concentrations in the environment. Trash in the environment, that's pollution. Chemicals both naturally occurring and synthetic, those are the real killers. We tend to think of pollution in terms of weird synthetic chemicals made in big chemical processing plants, and their certainly a problem, but as we'll see in a bit, you got to understand natural compounds in the wrong concentrations can do just as much damage as whatever [petro] insecticides we're making. One of the main ways we're alternating concentrations of natural compounds is by messing with the bio geochemical cycles that we talked about a couple of weeks ago. You're probable tired of hearing about it, but the most obvious cycle that were screwing up is the carbon cycle, which shuffles carbon around the planet into the various reservoirs. The atmosphere, oceans, rocks, the bodies of living things, the cycle keeps going on thankfully, but we're overloading it by digging up all that carbon rich coal, oil, and gas and burning it to fuel our 21st century lifestyles. All of a sudden there's more carbon getting released that the reservoirs can handle. Plants and animals are like we're cool, we got all the carbon we need. The oceans are like yeah, we're good on carbon too. It just can't go back into the rock, so, it hangs around in the atmosphere as a greenhouse gas. Insulating our planet and changing the climate. We've also be tampering with the nitrogen and phosphorus cycles to similar effect. Nitrogen and phosphorus are nutrients which we and other organisms need , like really need, in order to grow and respire and exist. When we go and make like ludicrous amounts of these nutrients available, the ecosystems get very confused. It's like the day in 5th grade when I realized that I could spend my entire allowance on Cadbury creme eggs at the after Easter candy sell at Walgreen's. It was fun at first, then it was not. Phosphates and nitrates are basically the main ingredients in fertilizers. Phosphates are also found in some detergents. When raised water, from our houses are run off from farms, washes those compounds into rivers and streams, it can cause huge alga balloon that choke out the rest of the plants, and animals in the stream, and totally gross looking. That's not the end of it. When all the phosphors and nitrogen are used up, the algae die, and then bacteria get started on decomposing that dead algae. Of course, the decomposers need oxygen, which they take out of the water. Then the oxygen levels in the water plummet killing all the fish and just about everything else that needs oxygen. This is how phosphate and nitrate pollution causes dead zones. The biggest example of this happening right this very minute is in the Gulf of Mexico, at the mouth of the Mississippi River. The Gulf of Mexico dead zone covers 18,000 square kilometers of River Delta in coastline, and is basically a swath of totally deoxyganated water caused by all the fertilizers from the entire Mississippi River basin, which drains 2.6 million square kilometers of land. Draining to this one point in the Gulf, the size of the dead zone fluctuates seasonally, as it depends on how much fertilizer is being used by pretty much half of the farms in America. So yeah, pollution isn't just synthetic compounds with like 17 syllable long names, sometimes their just imbalances of chemicals that we need for our survival. However, not all chemicals found in nature are good for us, in fact, we know mother earth comes up with some the most toxic stuff that you've ever heard of. Take cyanide for instance, it's in a lot of stuff that we come in contact with everyday. Foods like almonds, spinach, and Lima beans contain cyanide, and so, do the seed of apples, which you have heard, and the pits of peaches. Cyanide is useful to plants, because it's a primitive insecticide, causing a molecular asphyxiation preventing A bug cells from being able to use oxygen. It takes a lot more cyanide then you'd find in an almond to finish off a human. Guess what? We've figured out how to collect a whole bunch of cyanide in one place, because we really love gold. Gold, my precious. Mining operations use cyanide in large quantities in order to separate gold, silver, and other precious metals from the ore. The cyanide process of ore extraction ground up ore is sprayed with a cyanide solution, which dissolves the metal in the ore and draws it out. The solution is then collected and the precious metal was taken out. The by-product of all of this is, of course, a pile of cyanide laced rock powder aka, hazardous waste to deal with. Or, try to deal with. Mines do all kinds of stuff to reduce the concentration of cyanide in these leftovers called tailings. They try to convert the cyanide into less toxic cyanite. The toxin is never totally eliminated. Then it can end up leaking into the ground water supply, or it can just sit there and keep dissolving other toxic metals out of the rock that also end up in our water like mercury. Mercury is another important pollutant. It's super toxic, naturally occurring metal found in coal, among other places. It's just fine hanging when it's hanging out underground in a coal scene. When that coal is burned to make electricity the mercury is released into the air. Then the mercury falls on the land where it makes its way into ground water and eventually into the food chain. Especially, into the marine food chain. As a result only about 25% of the mercury released by US power plants and factories actually ends up in the US. The rest enters the global cycle, which most people end up ingesting by eating fish. Mercury acts a powerful neuro toxin in animals interfering with our brains and our nervous system. Finally, two more naturally occurring compounds that we keep pumping out are sulfur dioxide and nitrogen dioxide. The most common natural sources of these things are volcanic eruptions or the waste of some algae and bacteria. We release millions of tons of these things in the environment every year by burning fossile fuels like coal. When these compounds react with water vapor in the atmosphere they turn into sulfuric acid and nitric acid, and then return to the surface as acid rain. In soils, these acids can cause the release of natural but toxic elements like aluminum in water. They can poison the aquatic wildlife, and on land the acidity can cause animals eggs to not hatch, and plants to loose nutrients. Things have got significantly better since a lot of countries put a missions controls into place. For a while there back in 1980, rain in much of North America had the same ph as tomato juice. Which objectively speaking, is the grossest. That's how we're amping up the levels of naturally occurring chemicals to toxic levels. Of course, were also synthesizing chemical that mother nature never even dreamed of. They reek their own special brand of havoc. The problem here is choosing just one as an example, because there are so many different things. There's a whole class of chemicals called endocrine disruptors which we put in pharmaceuticals, pesticides, and plastics, but some of them are also just by-products of industry and agriculture. Endocrine disruptors like bisphenol A or bpa which baby bottle manufactures have been scrambling to take out of their products in recent years hang out in plastics, then leach into our drinks, or are flushed off of agriculture fields into rivers, or are just flushed down toilets when we pee them out, because their in some drug that we've been taken. The result is that they get into water ways sometimes in high concentrations. The animals there they just soak them all in. The endocrine system basically it is to your hormones, controls a vast ray of organisms functions, and as concentrations of EDCs have increased. We've spotted male fish in rivers all over the world with female reproductive tracts or testes that make eggs. Those fish are living in the water, but we are drinking it. People of all ages are susceptible to EDC but research suggest that those most at risk are fetuses and infants, because their organ and immune systems are still forming. Scientist are still studying that the developmental reproductive and neurological effects that these compounds are having on us, and as far as I'm concerned they can't do it fast enough. The chemicals we're making are effecting us in ways that we could guess, and also probably ways that we never even dreamed of. At the same time, we're rearranging where and how much some naturally occurring compounds are showing up, and that adds to those 5 other impacts that we're having on the biosphere. The past 2 weeks have been a real bummer. Hopefully an enlighten bummer. This leads us to the next stage of ecology, and the last lesson in this course Conservation Biology and Restoration Ecology which together comprise the science of saving our planet and ourselves from ourselves.