1. Chapter 19

2.   1.Define the term ecology, and explain why ecology is important.  2.List and describe three human-caused environmental problems.  3.Identify the five different levels of organization in ecology.  4.Explain the theme of interconnectedness.  5.Identify the importance of models to ecology. Objectives 19.1

3. Chapter 19: Introduction to Ecology No living thing can survive on its own. Every organism obtains what it needs to survive from other organisms and from the nonliving parts of its environment, such as water and air. Ecology is the study of the interactions between organisms and the living and nonliving parts of their environment. In Chapter 19, you will learn how living things depend on other living things for survival. You will also learn how each type of organism, or species, has its own unique way of surviving in its part of the environment and how humans have made survival more difficult for many other species. Although the field of ecology is relatively new, our ancestors who lived more than 10,000 years ago knew the benefits of understanding the environment. They needed to know about the different wild plants and berries as well as how to hunt for food. We may have a better understanding of the environment today than we did previously; however, our need for such knowledge has become even more urgent. In the last few decades, humans have caused serious changes in the environment. Today, humans still need an understanding of ecology to limit the damage that we do to the environment that keeps us alive.

4. The factor that has probably caused the most serious damage to the environment is our exploding human population. Between 1930 and 1996, the human population tripled, from 2 billion people to nearly 6 billion people. This rate of increase has never been matched on Earth. And we’re still growing. Scientists believe there may be 7.8 to 12.5 billion people in the world by 2050.

5. The growing human population may also be causing the extinction of many of the Earth's species. For example, 60 of the 100 species of native Hawaiian birds have become extinct since the first humans arrived on the Hawaiian Islands. In the last 2,000 years, about 20 percent of the world's bird species have become extinct. The last time so many species disappeared this quickly was 65 million years ago during the mass extinction of the dinosaurs.

6. Humans have caused other environmental problems as well. Use of chemicals called chlorofluorocarbons, or CFCs, have weakened the ozone layer. These chemicals react with ozone gas high in the atmosphere and reduce the ozone layer's ability to block out ultraviolet radiation from the sun. The UV radiation that penetrates the ozone layer causes sunburns and more than a half-million cases of skin cancer each year.

7. The atmosphere has also been changed in a way that is affecting the Earth's climate. Carbon dioxide is a natural and important part of the atmosphere. By trapping much of the sun's heat energy, carbon dioxide helps prevent the Earth from becoming too cold for life. By burning huge amounts of fuel each year, humans have increased the concentration of carbon dioxide in the atmosphere by about 25 percent in the last 100 years. As the extra carbon dioxide is trapping more of the sun's heat, the Earth's temperatures are rising. Since 1860, the average global temperature has risen about 0.6 degrees Celsius, or 1 degree Fahrenheit, and most scientists agree that this increase has been caused by higher levels of carbon dioxide in the atmosphere.

8. The biosphere [BIE-oh-SFEER] is the largest, most complex level of organization in ecology. It contains all life on Earth, as well as the land, air, and water that supports life. The biosphere is about 20 kilometers, or 13 miles, thick and includes everything from the bottom of the ocean up to 10 kilometers, or 6 miles, above the Earth's surface.

9. The biosphere is made of many smaller parts called ecosystems. An ecosystem includes all of the living and nonliving parts of an environment found within a particular area. In ecology, a community refers to all of the organisms living in a particular area. A community does not include the nonliving parts that were described under ecosystem or biosphere. A population includes only the members of a single species living in the same area at the same time. For example, all of the gray wolves living in Minnesota are a single population. The simplest level of organization in ecology is the organism.

10. A Key Theme in Ecology All organisms obtain what they need to survive from interactions with other organisms and the nonliving parts of the environment. Each organism depends on these interactions for survival, so every living thing is linked with other living things. With so many different organisms and environmental factors interacting, the study of ecology can quickly become very complex. To simplify their study, ecologists use models to help explain the natural world. An ecological model can be a diagram, a graph, a mathematical equation, or a computer program. All of these models help to make complicated ideas and problems easier to understand.

11.   1.Contrast abiotic factors with biotic factors, and list two examples of each.  2.Explain the importance of tolerance curves.  3.Describe some adaptations that allow organisms to avoid unfavorable conditions.  4.Explain the concept of the niche.  5.Contrast the fundamental niche with the realized niche Objectives 19.2

12. Biotic and Abiotic Factors Recall that ecosystems include living and nonliving parts. Ecologists call the living parts biotic factors and the nonliving parts abiotic factors. Biotic factors include all of the living things that can affect an organism. Abiotic factors include all of the nonliving things that can affect an organism. Temperature, humidity, oxygen, sunlight, and water are a few important abiotic factors. Each ecosystem has a different set of conditions, or biotic and abiotic factors, that affect survival.

13. Look at Figure 19-8. You can find the temperature range of an organism by watching it function at different temperatures. This information can be made into a graph, which is a type of ecological model called a tolerance curve. This is a tolerance curve for a species of fish. The red curve shows the speed of the fish at different temperatures. Look at the left part of the graph. At the lowest temperature, the fish is not able to swim at all. As you look from left to right, the speed of the fish increases as the temperature increases until you reach the middle of the graph. This is the ideal temperature for the fish. As you continue to look from left to right, the speed of the fish decreases as the temperature becomes warmer than the ideal temperature. At the highest temperatures, the fish is no longer able to swim.

14. Some organisms can adjust their tolerance to different conditions in a process called acclimation [AK-luh-MAY-shuhn]. Look at Figure 19-9. This graph shows another example of acclimation. The blue line represents the swimming speed of a goldfish raised at 5 degrees Celsius. Notice that this fish does not function very well at temperatures above 25 degrees Celsius. The red line represents a fish raised at 25 degrees Celsius. Its tolerance limits are higher, and its optimal range is at around 30 degrees Celsius. This fish has acclimated to life at higher temperatures.

15. Some organisms are able to control their internal conditions while the environmental conditions change around them. Temperature, light, moisture, and other abiotic factors may change dramatically in a matter of hours. Some types of organisms do not control their internal conditions. These organisms, which are called conformers, change internally as the environment around them changes. The body temperature of a desert lizard rises and falls as the temperature around it rises and falls. Unlike conformers, regulators are organisms that use energy to control some of their internal conditions. Regulators can keep their internal conditions at an optimal range while the environmental conditions change around them.

16. The Niche Each species has its own unique way of life, or niche. A species' niche includes the range of conditions it can tolerate, the type of habitat it prefers, and the way it obtains the needed resources of food, water, energy, and nutrients. The niche also includes how and when the species reproduces and the ways the organism interacts with the biotic and abiotic factors in the environment.

17. Sometimes a species’ niche can change over the lifetime of its members. For example, caterpillars crawl and feed on leaves. Organisms with large, broad niches are called generalists. One generalist is the Virginia opossum [uh-PAHS-uhm]. The opossum is found across much of the United States in a variety of habitats, and it feeds on almost anything. The specialist has a small, narrow niche. The koala of Australia, which feeds on only certain eucalyptus tree leaves, is a specialist. Specialists are more likely than generalists to become extinct because specialists do not tolerate environmental changes very well. Look at Figure 19-13. These two circles represent the fundamental niches of Species 1 and Species 2. Notice that the center of each circle is darker than the rest of the circle. This dark portion represents the realized niche, or the ideal conditions for the species. Toward the edges of the circles, conditions are less ideal. The two circles overlap near the edges only, which means that the two species share part of their fundamental niches but not their realized niches.