The first science course I took in college was ecology. I didn't have a clue how to be successful in a college class in that first semester of my freshman year, and I earned a D in ecology. I later retook the class and earned an A the second time. But I wanted to bring up this point to illustrate that you can do poorly in a science class and still go on to be a scientist. Anyway, back to the subject at hand, ecology. In this module, we'll talk about what ecology is and discuss our place in the ecosystem. In the next module, we'll apply ecological ideas to our daily lives and explore how seemingly simple activities like taking a plastic bag at a grocery store can influence other lifeforms around us. Ecology is the study of interactions. At the largest level, there's the biosphere. The biosphere is all parts of earth where life exists. It's the biggest most encompassing level. At the next level down, we have biomes which are large areas of a particular habitat, such as a river or a tundra. Perhaps you remember learning about the biomes in your high school biology class. Then we have ecosystems. Ecosystems include everything in a particular area that is living or biotic, and non-living or abiotic. For example, if we consider the alpine ecosystem in Rocky Mountain National Park, the plant and animal species, which are living or biotic, are well-suited for that cold, dry oxygen poor air, which is a non-living or abiotic factor. At the next level down, we have the community. This is the variety of different species in a given area. For example, in this image, we see moose, bobcats, beavers, and owls are all represented as part of a community. Population refers to the total number of organisms in an area. For example, in this image, we're referring to the total number of elk in the area, the population of the elk. At the smallest level we have, well, you, the individual organism. Population ecology is a nice example of where we see these concepts at play in our daily lives. Maybe you've heard about growing human population, or maybe about the population of a certain pest species in an area, or if an endangered species is bouncing back or not bouncing back. If you happen to a hunt or fish, you'll be familiar with getting a hunting or fishing license. These licenses are designed to help control populations. For example, let's consider deer populations in the context of deer hunting, which requires a hunting license. Hunting too many or too few deer can have major repercussions down the road. If too few dear are hunted, this means there are more deer car accidents, which can be very, very expensive. Deer also have a tendency to strip down all plants in a given area which can result in death of trees, which negatively impacts local ecology, something we'll come back to in a minute. One of the reasons why when you go to a national park or a state park for example, you'll see deer exclusion fences. This allows scientists to determine the impact of deer foraging in an area, and also give an area a chance to recover. However, if we hunt too many deer in a given season, then there's no hunting for next year. Because remember population is a factor of additions, births or migrations in, and subtractions, deaths or migrations out of a given area. If there's too much deaths, there's not enough individuals to repopulate, so there's not enough births and suddenly we have a collapse of the population. When we think about how populations grow and change over time, it's also important to consider reproductive cycles. For example, rodent populations tend to increase more rapidly than human populations because animals like mice reach reproductive maturity at about six weeks compared to about 14 years in humans and also have very large litter sizes. For example, most humans only have a single baby at a time, whereas mice have several individuals with each reproductive episode. Population size is limited by the amount of resources in an area. Resources can mean many different things. It can be the amount of food that's available, the amount of places or habitats where an organism can live. What happens if we take these limitations away? We see a boom in population numbers and sometimes there can be so many of a certain individual species that it can be to the detriment of other species in the area. For example, let's consider invasive species. An Invasive species is an organism, either a plant or an animal, that is introduced somewhere new. In these new locations, there's no longer restrictions on the population. Maybe there's more food here or maybe there's no natural predators in that area, so when we take these restrictions away, the population just explodes. This is different from an exotic species, which may be living in an area where it's not originally from, but it doesn't have a booming population that negatively impacts the native species. With international commerce and the ease of travel, invasive species have become a real threat to local ecologies and we see evidence of mitigation efforts as part of our daily experiences. Maybe you've been driving down the highway or you've visited a camp site, and you've seen signs about not moving firewood. This may be part of an effort to stop movement of the emerald ash borer. The ash borer is native to Asia and is thought to have been accidentally carried to North America when packing materials. Unfortunately, now that it's here in North America, it's decimating ash tree populations across the continent. For example, this is a picture of an ash tree that once stood on my in-laws property and it was killed by the emerald ash borer. If you look closely at this picture, you'll see serpentine marks in the bark and this is the hallmark of trees that are killed by the emerald ash borer. If you enjoy boating or fishing, you may be familiar with [inaudible] zebra mussels. Shown in this picture is someone cleaning a boat to remove zebra mussels. Zebra mussels are another invasive species that are originally from Eurasia and they're thought to have been introduced to the Great Lakes Region of the United States via ballast tanks on ships. Unfortunately, they're decimating the balance of life in the Great Lakes and are also now found in other areas of the United States as well, including my home state of Colorado. If you live in an island nation, you may be familiar with rigorous regulations and security procedures for entering or leaving the country. Certain animal products like fruits and cheeses are not allowed into the country to prevent the spread of invasive species or novel diseases. Studying populations is a critical service that ecologists provide to society. For example, how do we know the mitigation efforts to prevent the spread of zebra mussels and the emerald ash borer are working? We need to be able to track populations and then adjust as necessary. For example, nutria are another example of an invasive species that are found in Louisiana and one way their population is controlled is through hunting. Florida also runs similar hunting programs to try and decrease the population of the invasive Burmese python. We need the work of population ecologists to know if these efforts are working or not. Community interactions, the next highest level above the population, is also important to consider when determining ecological health. One of the reasons the East Coast of the US has a deer population problem is that because the populations of the apex predators like lions or wolves is either very low or nonexistent. This brings us to one of the ecological tensions that we'll be discussing in this course. It seems like it would be a good thing to have fewer apex predators around. They could attack your livestock, your pets, or your children. It's better to have innocuous animals like deer around. They're not going to hurt me. But having too many deer results in it's own problems. As I mentioned earlier in this lecture, dear strip down young trees and can kill them, and then without those trees, now we've lost habitat or places to live for other animals such as birds or squirrels. Also as mentioned in course 2, trees are really important for pulling carbon dioxide, which is a greenhouse gas, out of the atmosphere. We end up having a ripple effect across the entire ecosystem, just because there are too many deers eating and killing trees. Calling the apex predators seems like a very large way that we can impact our ecological system. But the simple consumer decisions we make every day can also have a large impact on the ecological system. What are these simple consumer decisions? What are the things that we run into everyday? That will be the question that guides the focus of the next module.
