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Chapter 19 Introduction to Ecology Ecology – the study of the interactions between organisms and the living and nonliving parts of their environments. Today’s Issues - The study of ecological information has been around for a very long time. - Over the past few decades, humans have changed the environment on a greater scale than ever before in history. 1. The Exploding Human Population - The current world population is: 6,592,491,071 - The increasing population leads to overcrowding; we need more food, more energy, more space to live, and more space for disposal of waste. 2. The 6th Mass extinction - As the human population increased, many other species have declined in numbers or become extinct. o All due to habitat destruction, over hunting, and introduction to diseases and predators. - There is fossil evidence about 5 previous mass extinctions; we are causing the 6th. o This extinction is happening faster than any of the previous extinctions. o Scientists estimate that about 1/5 of the species in the world may disappear in the next century. 3. The Thinning Ozone layer - In 1985, British scientists discovered a hold in the ozone layer over Antarctica. - In 1992, there was a treaty formed that banned the use of CFCs and other ozone-destroying chemicals. o It’s important to note that normal ozone lets through about 1% of the sun’s UV radiation. Think about how many sunburns are caused or how much skin cancer is caused just because of that 1%. 4. Climate Changes - The Greenhouse Effect – the mechanism by which greenhouse gases, such as carbon dioxide and water vapor, trap heat in the upper atmosphere and deflect it back to Earth, thereby insulating the Earth and overheating it. - The burning of fossil fuels (coal, oil, and natural gas) has caused the concentration of CO2 to increase 25% in the last 100 years. - Since 1860, the average global temperature has risen about 0.6oC (1oF). - It is estimated that by the year 2100, the average global temperature will rise about 1.5 – 4.5 oC (3-8oF) o This increase in temperature will be sure to cause rising sea levels due to the melting of the polar ice caps. Levels of Organization - Scientists recognize a hierarchy of different levels of organization within organisms. - Each level has unique properties that result from interactions among its components. The Biosphere - The most inclusive level. - It is the thin volume of Earth and its atmosphere that supports life. o It’s about 20km thick and extends about 8-10km above the Earth’s surface to the deep parts of the oceans. Ecosystems - All the organisms and the nonliving parts of the environment found within a particular place. o Example: a pond Communities, Populations, and Organisms - A community is all the interacting organisms living in an area. - A population includes all of the members of a single species that live in one place. - The simplest level of organization is that of the organism. A key theme in Ecology - It is important to remember that when you study Ecology, no organism is isolated. The theme of interconnectedness of all organisms is central to the study of Ecology. - Each ecosystem is a network in which organisms are linked to other organisms and to the nonliving parts of the environment. - Any disturbance or change in an ecosystem can spread through the network of interactions and affect the ecosystem in widespread and often unexpected ways. Ecological Models - Ecosystems are extremely complex and difficult to study. One way Ecologists deal with this complexity is to use models. - A model may be visual, verbal, or mathematical. They are often based on predictions. - A model can be used to test a hypothesis. o For example, predicting future behavior of the ecosystem. - Models are often used to help plan and evaluate solutions to environmental problems. Section 19.2 Ecology of Organisms - Answers to complex questions about ecology involve looking at the organism’s evolutionary history, its tolerances and requirements, and the history and conditions of its habitat (where it lives). Biotic and Abiotic Factors - Biotic factors are the living components of the environment and include all of the living things that affect the organism. - Abiotic factors are the physical and chemical characteristics of the environment. o Temperature, humidity, pH, salinity, oxygen concentration, etc. - These factors are not independent of one another. Organisms change their environments and are influences by it. The changing environment - Abiotic factors are not constant. They vary from place to place and over time. o Example, think about how quickly temperature can change and how different the temperatures are across the country and world. Responses to a changing environment - Organisms are able to survive within a wide range of environmental conditions. - Ecologists measure how well an organism can survive at extremes by measuring how well it performs its functions at those extremes. o A graph of performance can then be constructed. This graph is called the organism’s tolerance curve. o An organism cannot live in areas out its tolerance limits. Acclimation - Some organisms can adjust their tolerance to abiotic factors through the process of acclimation. o For example, if you spend a few weeks at high altitude, your body will “acclimate’ (adjust) to the reduced oxygen level. Over time, your body will start producing more RBCs to increase the amount of oxygen in your body. Control of Internal conditions - There are 2 ways for organisms to deal with some changes to their environments: they can become a conformer, or a regulator. o A conformer does not change their internal environment, but rather they change their external environment. o A regulator is an organism that uses energy to control some of their internal conditions. They’ll try and keep their internal conditions within optimal range over a wide variety of environmental conditions. Escape from unsuitable conditions - Some species can survive unsuitable conditions by escaping from the temporarily. o For example, some organisms become dormant. They enter a state of reduced activity during periods of unfavorable conditions. - Another escape strategy is to migrate. o To move to a more favorable environment. Resources - Whether a species can survive in a particular habitat depends on the suitability of environmental conditions and also the availability of resources. o Resources – the energy and materials the species needs to survive. The Niche - A species’ niche is its way of life, or the role the species plays in its environment. - It includes a wide range of conditions that the species can tolerate, the methods by which it obtains needed resources, the number of offspring it has, its time of reproduction, and all of its other interactions with its environment. - The fundamental niche is the range of conditions that a species can potentially tolerate and the range of resources it can potentially use. - The realized niche of a species is the range of resources it actually uses. Niche Differences - A species’ niche can change within a single generation. o Example – caterpillar to butterfly. - Generalists are species with broad niches; they can tolerate a range of conditions and use a variety of resources. - Species that have narrow niches are called specialists.