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Earth at the Crossroads: Understanding the Ecology of a Changing Planet

Earth at the Crossroads: Understanding the Ecology of a Changing Planet

Professor Eric G. Strauss Ph.D.
Loyola Marymount University
Course No.  1720
Course No.  1720
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Course Overview

About This Course

36 lectures  |  30 minutes per lecture

Every plant, microorganism, and animal on Earth exists within an ecosystem: a complex network of interdependent relationships in which each individual strand is important and contributes to the success of the whole. Ecosystems, in turn, interact with one another to form the biosphere: the zone of life on our planet.

But these systems, so important to the world around us, are far from stable. Instead, ecosystems are constantly changed by the pressures of biological, geological, and physical forces. In addition, the rapid growth of human populations and their attendant technologies has created unprecedented forces of ecological change. Only when you look beyond the individual level and observe how populations of different species interact with themselves, with other species, and with their physical environment, as well as how they respond and adapt to change, can you fully understand how life truly works.

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Every plant, microorganism, and animal on Earth exists within an ecosystem: a complex network of interdependent relationships in which each individual strand is important and contributes to the success of the whole. Ecosystems, in turn, interact with one another to form the biosphere: the zone of life on our planet.

But these systems, so important to the world around us, are far from stable. Instead, ecosystems are constantly changed by the pressures of biological, geological, and physical forces. In addition, the rapid growth of human populations and their attendant technologies has created unprecedented forces of ecological change. Only when you look beyond the individual level and observe how populations of different species interact with themselves, with other species, and with their physical environment, as well as how they respond and adapt to change, can you fully understand how life truly works.

Now, with Earth at the Crossroads: Understanding the Ecology of a Changing Planet, you can explore the rich interconnections that make up the great and fascinating web of life on Earth. In this compelling 36-lecture course, behavioral ecologist Eric G. Strauss of Boston College provides you with a comprehensive overview that is a hallmark of the study of ecology. With Professor Strauss as your guide, you'll investigate the remarkably complex workings of Earth's biosphere and learn about the myriad forces that shape the world's habitats, from the movement of water and nutrients within an ecosystem to the reproductive strategies employed by plants and animals around the world.

As you delve into the biosphere's intricate network of relationships, you develop a deeper appreciation of the rich complexity of the life around you. You'll also strengthen your understanding of some of the most important debates in current affairs, including questions of climate change, protection of endangered species, and alternative energy sources. Earth at the Crossroads exposes you to the science behind these debates, allowing you to develop your own opinions and back them up with the latest scientific evidence.

Examine Ecology's Most Intriguing Questions

The key to understanding and bringing to life these relationships lies in the field of ecology. A science that has come into its own during the modern era, ecology helps humans comprehend—and put into a more coherent perspective—the "big picture" of life on Earth.

In Earth at the Crossroads, you examine the same intriguing questions that ecologists themselves contemplate as they study life from this unique perspective:

  • What forces shape the living systems around us?
  • How do relationships like predation and competition affect communities of organisms?
  • What happens when a new organism is introduced into an environment?
  • How does climate change affect plants and animals in a single ecosystem—or even the world at large?

And perhaps the most crucial question of all:

  • What role do you as a member of Earth's living community play, and how can you use your understanding of these complex patterns to ensure that you and your fellow organisms survive and thrive?

The field of ecology is an applied science whose impact can be felt in a range of areas. The knowledge gained from the study of Earth's living systems has allowed us to

  • conserve endangered habitats,
  • more wisely manage our natural resources,
  • produce higher and healthier yields of agriculture,
  • better prepare for public health concerns, and
  • understand how highly artificial environments such as major cities follow the same rules as more "natural" environments.

Understand the Complexity of Life on Earth

Earth at the Crossroads opens with an introduction in which you explore the development of ecology as a scientific discipline distinct from biology and other related areas of study. Through vivid examples and accessible explanations, Professor Strauss explicates the field's key theories and raises thought-provoking questions that motivate scientists in this vital area of study.

Next, you move into the fundamental topics covered in the field, which are explored in three units:

  • In lectures 5 through 18, you examine the important forces that impact ecosystems, such as the way energy, nutrients, and water are used and recycled in these systems.
  • In lectures 19 through 32, you focus on specific ecological interactions and processes, including microevolution, population growth, migration, disease, and coevolution.
  • In lectures 33 through 36, you consider some of the latest scientific contributions that suggest how we can intervene in ecosystems in a beneficial way.

Throughout the course, you also learn about the remarkable and often surprising ways that organisms compete, coexist, and cooperate:

  • The interaction of ants and aphids: Living in a relationship not unlike that of the farmer and the dairy cow, ants harvest the nutritious fluid that aphids suck from plants while protecting their wards from predators.
  • The survival strategies of the Monarch butterfly and its imitators: Monarchs feed on poisonous milkweed, which makes them toxic to predators, a fact they signal with their bright coloration. Other species have developed similar markings to "trick" predators into leaving them alone.
  • The surprising relationship between wolves, elks, and river ecosystems in Yellowstone National Park: When the park's wolves were almost hunted to extinction, populations of elk skyrocketed while nearby river ecosystems declined. Freed from the pressure of predation, the elk were able to graze these fragile ecosystems, damaging them significantly. When wolf populations were restored, the elk returned to their traditional habitats, and the river systems revived.
  • The paradoxical relationship between humans and bacteria: As people increasingly use antibacterial soaps, antibiotics, and disinfectants to protect themselves against microbial disease, they drive these organisms to develop a tolerance to these products, putting human beings at an even greater risk of infection by "superbugs."

As you explore these fascinating examples, you experience the sense of wonder that is at the heart of the study of ecology.

The Whole Earth: City and Country

Delving deeply into ecology, you quickly see that this field of study extends beyond what we usually think of as "nature." Ecologists espouse a "whole Earth" view that incorporates both pristine wilderness regions and modern urban settings. From this perspective, the city is simply another form of ecosystem, alive with organisms that are interconnected in complex relationships.

You examine how wildlife adapts to new urban settings, as seen in the example of hawks that thrive on the tops of skyscrapers and feed on urban pigeons. Earth at the Crossroads also illuminates how city settings can generate their own microclimates, evidenced in the "heat island effect," in which the reduced greenery and increased hot, bare surfaces produce higher urban temperatures.

This examination of life in the modern world also takes you to the suburbs, where you'll discover an abundance of life forms dwelling in complicated relationships that rival the complexity of wilderness communities.

Professor Strauss is the perfect guide for exploring the ecological implications of our modern world. As a specialist in urban ecology, he brings classic and cutting-edge scientific studies to bear on his consideration of urban populations, suburban spread, and the ways in which human populations affect and are affected by the ecosystems in which they live.

Humankind's Place in the Biosphere

As you ponder life in these varying ecosystems—both wilderness and urban—you ultimately arrive at an intriguing question: What role does humankind play in this great web of life?

As Professor Strauss explains, humanity has a unique role in the world. We have an unprecedented capacity to shape the biosphere and make thoughtful, informed choices about the actions we take.

In this course, you see how human history is full of examples of how we as a species have changed the world around us, from the development of agriculture to the spread of often-dangerous chemicals that can alter the genetic material of living organisms. But it's also a history of successes and solutions, as innovative scientists and engineers have developed new technologies and practices that allow humankind to thrive while reducing our impact on other species.

As Professor Strauss considers the role humans play in the biosphere, he provides examples of both humankind's mistakes and innovations. The result is a thoughtful and balanced consideration of the role of humanity within Earth's living communities—one that will allow you to develop better-informed opinions regarding crucial questions about the world in which we live.

The Great Web of Life Made Accessible

The goal of ecology is to provide a comprehensive view of the world as an interconnected complex of relationships. In Earth at the Crossroads, this complicated topic is made accessible by an experienced and accomplished instructor. Professor Strauss provides an engaging and thorough overview of this intriguing field of study through the use of compelling anecdotes, easy-to-follow explanations, and helpful visual aids. A leading scholar and researcher in urban ecology, Professor Strauss presents cutting-edge findings that encourage a "whole world" perspective on life on this planet.

Join Professor Strauss as he traces the fascinating links that are at the heart of the study of ecology. You'll discover new ways to view the world of surprise and wonderment that exists all around us in this great web of life.

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36 Lectures
  • 1
    An Ecological Diagnosis of the Living Earth
    What is ecology? This introductory lecture considers key topics and concepts you'll encounter as you study the complex interactions of Earth's biosphere—and raises the question of humankind's place within this great network of relationships. x
  • 2
    Humanity and the Tragedy of the Commons
    Although human beings are a relatively young species, we have had a huge impact on the planet we inhabit. Here, consider some of the ramifications of this effect, focusing on a fundamental principle of ecology, the Tragedy of the Commons, and see this principle at work in the fishing industry. x
  • 3
    Ecology—Natural History to Holistic Science
    In the last century, ecology emerged as a new area of study that draws from diverse disciplines, including natural history, biology, botany, and zoology, to forge a holistic understanding of life on earth. Chart the history of this burgeoning field and the great minds that shaped its development. x
  • 4
    Ecology as a System—Presses and Pulses
    All ecosystems are constantly in flux. Begin to explore the biological, geological, and physical forces that drive change in the Earth's ecosystems, and develop an appreciation of the important role played in ecology by social factors, including public policy and shifts in human demography. x
  • 5
    Climate and Habitat—Twin Ecological Crises
    Apply what you learned in the last lecture about the forces of change within the Earth's ecological system to understand two crucial aspects in today's world: climate change and habitat destruction. x
  • 6
    Human Society as Ecological Driver
    Human power structures, social organization, information flow, and cultural practices can profoundly change the shape of ecosystems. Examine the role of humans as "ecosystem engineers" as you look more closely at some of the social forces and practices that affect the ecology of our planet. x
  • 7
    Movement of Energy through Living Systems
    Begin your consideration of specific forces that cause ecosystem change by examining the flow of energy. You trace how energy moves through ecosystems, from sunlight through the transitions of food production, consumption, and decomposition. x
  • 8
    Humans as Energy Consumers
    Humans are the most voracious consumers of energy on the planet, and our appetite for energy produces enormous short- and long-term challenges to ecological sustainability. Investigate human energy consumption habits and examine alternatives to traditional ways of accessing energy. x
  • 9
    Nutrient Cycling in Ecosystems
    While energy moves from the sun through organisms and is ultimately lost to the atmosphere, crucial organic molecules are recycled endlessly. Learn how two of these essential building blocks of life—carbon and nitrogen—move through the ecosystem. x
  • 10
    The Challenges of Waste and Disposal
    Just as organic nutrients remain in the environment, so, too, do the byproducts of human life. Consider the impact of human trash on the environment and examine alternatives to the current strategies of waste disposal. x
  • 11
    The Water Cycle and Climate
    Water, like all other molecules in ecosystems, is recycled endlessly. Investigate the process by which water circulates through the ecosystem and examine the role water plays as a living system in pollution abatement and long-term sustainability. x
  • 12
    Human Water Use and Climate Change
    Human water consumption is growing at an astounding rate. The depletion of water resources threatens ecosystems, contributes to changes in climate, and renders human communities more vulnerable to disaster and disease. Examine how human behavior is affecting water reserves and explore strategies for conserving this precious resource. x
  • 13
    Rain and Heat—Forces That Shape Climate
    Why do some regions develop desert climates, while others become rainforests? What adaptations must organisms make to survive in these habitats? Examine the role of water and weather in determining the characteristics of different ecosystems, and learn how organisms develop mechanisms to thrive in extreme environments. x
  • 14
    The Ecology of Global Climate Change
    Most experts in climatology agree: The Earth is rapidly warming, and while the causes are complex, human technology is most likely contributing to this trend. Investigate the role of climate change on shifting animal migratory patterns, life-cycle fluctuations in plants, and the disappearance of marine habitats, and consider ways to reduce the impact of climate change on the Earth's ecosystems. x
  • 15
    How Living Organisms Acquire Food
    Return to the topic of energy flow within ecosystems to consider the interaction between producers and consumers within a complex pattern called the food web. Examine how this relationship shapes plant distribution and animal behavior, and consider what happens when these systems experience stress due to ecosystem fragmentation and species extirpation. x
  • 16
    The Ecological Consequences of Agriculture
    The current model for food production and distribution in developed countries creates a large and growing burden on the Earth's biosphere. Explore the role of modern large-scale agriculture in the dynamics of ecosystems, and consider alternative models for food production and delivery. x
  • 17
    Food, Energy Flows, Biomagnification
    One effect of the food web is that nutrients and chemicals become concentrated in organisms at the top of the food chain. In this lecture, learn how this process, called biomagnification, both benefits living organisms and leads to the concentration of toxic substances, including DDT and PCBs. x
  • 18
    The Human Ecology of Biomagnification
    Take a closer look at some of the negative effects of biomagnification that can be traced to human activity. Examine several examples of human-influenced biomagnification, including the appearance of organic pollutants in human breast milk and the notorious case of mercury poisoning in the human and animal populations of Minamata Bay, Japan. x
  • 19
    The Ecological Community as a Living Mosaic
    Local ecological communities are complex aggregations of living and nonliving forces. Take a look at these living mosaics by exploring predator and prey relationships, interactions of competition and cooperation, and the effect of large-scale disturbances such as fires and flood. x
  • 20
    Wildlife Adaptation to Human Landscapes
    Following World War II, suburban living spread in human populations, fragmenting wildlife habitats and disrupting ecosystems near urban landscapes. Examine the effects of increasing urbanization and the strategies species develop to adapt to ecosystems now dominated by human communities. x
  • 21
    Biodiversity, Disturbance, Invasive Species
    One of the elements that can help bring stability to an ecosystem is biodiversity, or the diversity of life within an ecosystem. Here, begin to consider the phenomena that impact biodiversity, including forest fires, deforestation, and competition posed by the invasion of nonnative species. x
  • 22
    Biodiversity Decline and Restoration Ecology
    As human populations have soared, urban areas have expanded to accommodate more residents. In this lecture, explore the effects of urbanization on local and regional biodiversity as well as actions that can mitigate negative impact and enhance local ecosystems. x
  • 23
    Microevolution and Biological Variation
    Healthy populations of organisms have enough genetic variability to withstand ecological change. Examine the processes and conditions that contribute to the production of biological variation within a population and how that variation can help stabilize the entire ecosystem. x
  • 24
    Human Impacts on Ecological Space and Time
    As humans carve up landscapes and reshape them with nonnative plants and animals for their own use, biodiversity in those areas decreases, leaving native species subject to extinction. Consider what is lost when the biodiversity is suppressed, and explore ways in which humans can coexist with healthy local ecosystems. x
  • 25
    Population Growth and Its Natural Limits
    No aspect of ecology is more fundamental to resiliency than the way in which natural populations grow. Examine the models that help describe population growth, and review the different strategies and behaviors that species have developed to maintain population size and support the resiliency of their habitats. x
  • 26
    The Human Shift to an Urban Lifestyle
    Humans have undergone a massive demographic transition as over half of the human population has moved from rural to urban lifestyles. Investigate how this shift has created a unique set of ecological characteristics, and consider the challenges posed by urban infrastructure on environmental sustainability. x
  • 27
    The Ecology of Dispersal and Migration
    In response to seasonal conditions, the threat of predators, mating behaviors, and the availability of food, some organisms have to move long distances in order to complete their lifecycles. Here, explore the costs and benefits of migration and consider the challenges organisms face during these long, dangerous treks. x
  • 28
    Human Impacts on Animal Migration
    Human land-use practices have disrupted the migratory patterns of many species, which are now threatened with extinction as a result of this disruption. Investigate the unique ecological requirements of migratory species, as well as some of the management strategies to facilitate animal movement across urbanized landscapes and agricultural ecosystems. x
  • 29
    Ecology and Economy of Sex and Reproduction
    Why do organisms reproduce sexually? What is gained by this costly and often risky form of reproduction? What behaviors have species developed to mitigate those risks? Explore these questions and develop an understanding of the ecology of reproduction and its implication for ecological sustainability and biodiversity. x
  • 30
    Cities and the Human Demographic Transition
    Shifting demographic patterns toward industrialization and urbanization have dramatically reduced the size of nuclear families all over the world. Explore the ecological forces that select for large and small families among the human species and what this phenomenon suggests for our future sustainability. x
  • 31
    Coevolution among Species
    Many species live so close to each other that they affect each other's evolutionary trajectories through a process called coevolution. Analyze the many forms of coevolution, including mutualism, predator-prey arms races, mimicry, camouflage, and deception, and consider how the rapid decline of the world's ecosystems places these relationships in peril. x
  • 32
    The Coevolution of Human Diseases
    Take a closer look at a particular example of coevolution: the development of zoonotic diseases (diseases that spread from animals to people) in human beings, including Lyme disease and West Nile fever. Also, learn how climate change and habitat fragmentation affect the spread of infectious diseases. x
  • 33
    Strategies for Reversing Ecosystem Decline
    In conservation biology and restoration ecology, scientists study how to sustain natural ecosystems and preserve the populations of declining species. Review some of the ways experts have sought to rebuild damaged habitats as you consider current debates about the efficacy and ethics of these interventions. x
  • 34
    Designing Spaces for Wildlife
    Continue your examination of conservation biology with a consideration of park design and the effort to preserve green spaces. Since precious resources go into conservation, scientists and policymakers must make difficult decisions about which species to include in recovery plans. x
  • 35
    Toward Sustainable Urban Ecosystems
    As human populations grow and evolve, the need to make conscious, positive transformations in the way people live becomes increasingly important. Explore the new field of urban ecology as it seeks to understand and improve the ecology of cities around the world. x
  • 36
    Recovering Ecosystems—Hope for the Future
    While human activity has put many habitats at risk, much is being done to heal damaged and threatened ecosystems. Examine some of the ways ecological thinking and action can simultaneously preserve these habitats and enhance the health and well-being of human communities. x

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Eric G. Strauss
Ph.D. Eric G. Strauss
Loyola Marymount University

Dr. Eric G. Strauss is Presidential Professor in Ecology at Loyola Marymount University in Los Angeles. He is one of the founding science directors of the Urban Ecology Institute at Boston College, where he previously was Director of the Environmental Studies Program and Research Associate Professor. He received his undergraduate education at Emerson College and earned his Ph.D. from Tufts University. An active researcher, Professor Strauss has been an investigator on a number of groundbreaking collaborative studies, including a study of the conservation biology of piping plovers and studies of the eastern coyote and diamondback terrapin. He serves as the editor-in-chief for the journal Cities and the Environment and continues to research and participate in collaborative activities at the Urban Ecology Institute. In addition, Professor Strauss was lead author on a nationally successful biology textbook, Biology: The Web of Life, and hosted the accompanying video series, Biology Alive! Dr. Strauss also served on the Barnstable Conservation Commission and on the boards of directors for the Cape Cod Museum of Natural History and the Association for the Preservation of Cape Cod.

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Reviews

Rated 3.5 out of 5 by 13 reviewers.
Rated 3 out of 5 by Good Material but Disjointed The professor is extremely well versed, invested in the subject, and non-judgemental in our handling of the environment. However I found it difficult to focus much of the time because it was somewhat disjointed. Although he gave examples of points throughout the course, I would like to have seen more "structure" either in the beginning of the lecture or a recap at the end - I lost my train of thought (and learning!) with all of the tangents taken for examples (which were important but refocusing should have been done). Although the use of slides was appropriate, with many excellent photos, again, I lost the context of the conversation. I "powered" through the course because I felt it important to at least hear and understand the issues at hand, but felt my recall of the course simply wasn't good whereas from many other courses, was excellent. I think the course should have been confined to 24 lectures and my guess is most of the salient points could have been made. You won't make a mistake purchasing the course, and I would do it again, but improvements could certainly be made. January 18, 2014
Rated 2 out of 5 by Earth at the Crossroads Of all the courses purchased to date, this course presented the least amount of new information or information that could be used.Many of the lectures seemed to bled into each other without creating interest. The professor fine, but content seemed to be stretched without real purpose. I would not recommend this course to others. November 7, 2012
Rated 2 out of 5 by Very disappointing The pace is slow. The content is generic, vague and redundant. The presentation is totally uninspiring. A shame given the importance of the topic. October 1, 2012
Rated 5 out of 5 by Ecological goldmine! DVD review. ©2009. Guidebook 123 pages. OMG! This was a fantastic journey, and I’m so glad to have gotten this one. I had reservations at first due to some pessimistic comments; but the topic has always been an interest of mine, so couldn’t resist. First off, I want to review Dr Strauss. Sure, like any other presenter, he could reduce the number of times he says, “You know” and “um.” Actually it didn’t bother me at all. When he is on a roll and really caught up in the spirit of the lecture, there are very few of them. I found Dr Strauss to have very good presentation skills: he uses hand and body gestures very naturally; in fact, he often uses his entire body to convey information. Eye contact I rate an A+ because he made me feel like he was lecturing in my living room just for me. He’s very enthusiastic, clearly loves what he does, and I found his excitement contagious; furthermore, he comes across as highly knowledgeable and genuinely affable, especially as each lecture closes. He uses a lot of metaphors and analogies. He’s got a sizeable vocabulary (which I appreciated), so this ain’t dumbed down. I learned a lot as far ecological jargon goes. Organization: This course isn’t as typical as other TGC courses, which are usually arranged chronologically or thematically. It’s roughly divided into three parts: (1) scientific principles or ecological drivers, (2) integrated processes or communities, (3) human responses to environmental concerns. Moreover, many lectures alternate, with one being scientific and the other highlighting human interaction with that principle; in essence, theory comes first, and then putting theory into realm of practice. Broadly speaking, I found the course to be well organized in that it also moves through Bloom’s Taxonomy, with a heavy emphasis on analysis, synthesis, and evaluation. If you’re used to courses hovering around the lower-order domains of knowledge and comprehension, then you might not easily absorb the content. You’ve got to actively connect the dots. Content: Loved it. Couldn’t get enough, in fact. Every lecture had gads of research, data, charts, graphs, pictures, and realia such as turtles, butterflies, etc. One extra bonus for me was having so many research experiments described in detail, especially those illustrating how ecologists go about collecting data. I’ve often wondered about that. Loved how he brought the course full circle. He began early on discussing “tragedy of the commons” and ended on a similar topic. Every day when you step outside you can’t help but notice what you once took for granted--even singing birds-- and contemplate just how interconnected and interdependent the world really is. If you’ve read about the debates over the reintroduction and impact of grey wolves in Yellowstone, you’ll get a good deal of issue here, including the part you don’t hear about in the news. This course turned out to be one of the most practical TGC courses I’ve viewed. Cons? (1) The Guidebook was slim, with each lecture getting at best two pages of bare bones outline, and (2) too many references to what would be discussed later in upcoming lectures. Other than that, I was thoroughly delighted with this one. June 14, 2012
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