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Study of the Global Ecosystem Section 34.1
What is Ecology? • The scientific study of the interactions among organisms and between organisms and their environments is called ecology.
Five Levels of Ecological Study: • The smallest unit of ecological study is the individual organism. – Ecologists study the adaptations that enable organisms to meet the challenges posed by their environments. • A population is a group of individual organisms of the same species living in a particular area. – Ecologists seek to identify factors that affect the size and growth of a population.
Five Levels of Ecological Study: • All of the organisms inhabiting a particular area make up a community. – Ecologists investigate interactions among the organisms in a community. • How do different species of algae­ eating fish compete for food? • How do desert plants compete for limited water resources? • An ecosystem includes the abiotic factors and the biotic factors in an area. – Questions at the ecosystem level may relate to the flow of energy and chemicals. • How does nitrogen move within the reef ecosystem? • Where will pollution move to and what effects will it have?
Five Levels of Ecological Study: • The broadest level of ecological study is the biosphere. The biosphere is the sum of all Earth's ecosystems. • You can picture the biosphere as the "envelope" of air, land, and water that supports and includes all life on Earth. • The Biosphere includes: – the atmosphere to an altitude of several kilometers; – the land to a depth of about 2 kilometers; – lakes and streams; and the oceans to a depth of several kilometers. • Questions at the biosphere level involve global issues, such as – investigating the effects of climate change on living things.
Distribution of Habitats within the Biosphere: • Looking at Earth from a space shuttle, you would see that the biosphere is "patchy"—like a quilt of different environments, including land and oceans, lakes and ice. • Observe just one continent, and you would see an uneven distribution of ecosystems such as deserts, grasslands, forests, and rivers.
Distribution of Habitats within the Biosphere: • A still smaller area, such as the Lake Tahoe Basin, may contain patches of woods, fresh water, and marshes. • All these environmental variations are due mainly to differences in abiotic factors such as temperature, soil type, and the availability of water and light.
Distribution of Habitats within the Biosphere: • This patchiness creates a number of different habitats, or specific environments in which organisms live. Each habitat has characteristic abiotic and biotic factors. • Kiwa Beach includes several habitats: patches of forest, marshy areas, a stream, and the lake. – The forest patches are home to trees and certain species of birds and animals.
Distribution of Habitats within the Biosphere: • Kiwa Beach includes several habitats: patches of forest, marshy areas, a river, and the lake. – The forest patches are home to trees and certain species of birds and animals. – The marshy land areas provide a habitat for many species of prokaryotes, fungi, and insects that live in and on top of the wet soil. – Within the river habitat is a surface "microhabitat" that supports floating plankton and swimming animals – The deeper lake water is a separate microhabitat, with different light and temperature conditions and a different community of organisms.
Key Factors that Effect Biotic Distribution: • The organisms that inhabit the Lake Tahoe Basin are adapted to the conditions of forest habitats. These abiotic factors include sunlight, water, temperature, soil, and wind. • Sunlight The sun provides light and warmth and is the energy source for almost all ecosystems on Earth. • Sunlight powers photosynthesis by plants. • Much less sunlight reaches the forest floor than reaches the tops of the trees. This varying amount of sunlight creates different microhabitats. • In aquatic (water) environments, sunlight provides energy for photosynthetic producers such as algae. This affects where algae live within a lake or ocean.
Key Factors that Effect Biotic Distribution: • Water is essential to all life on Earth. All organisms contain water—in fact, you consist of nearly 70 percent water! – Among its many important properties, water can dissolve gases such as oxygen and solutes such as salt. • Terrestrial organisms have adaptations that keep them from losing too much water and drying out. – For example, pine trees have needle­shaped leaves with a waxy coating. These leaves minimize the amount of water that evaporates into the air. • Aquatic organisms also must balance their water uptake and water loss.
Key Factors that Effect Biotic Distribution: • Temperature Most life exists within a fairly narrow range of temperatures, from about 0°C to about 50°C. – Few organisms can maintain an active metabolism below 0°C. – Most organisms' enzymes are denatured (they lose their shape and stop working) above 50°C. • Soil is the product of abiotic forces (such as ice, rain, and wind) and the actions of living things (such as microorganisms, plants, and earthworms) on the rocks and minerals of Earth's crust. The structure and chemical makeup of soil and rock in an area affect the types of plants that grow there.
Key Factors that Effect Biotic Distribution: • Wind can affect the distribution and the activities of organisms in several ways. – Wind moves clouds and rain over Earth's surface. – Wind also stirs up water in ponds, lakes, and streams, creating currents that bring up nutrients from the bottom. – Many land plants depend on wind to help disperse their pollen and seeds.
Key Factors that Effect Biotic Distribution: • Severe Disturbances Major natural disturbances that affect ecosystems include fires, hurricanes, tornadoes, drought, floods, and volcanic eruptions. • Some disturbances, such as volcanic eruptions, are so infrequent that organisms have not acquired evolutionary adaptations to them. • Other disturbances, such as fires, occur frequently in some communities. Many organisms in such communities have adapted to these disturbances. – In dry scrublands where fires are common, many plants can regrow from their roots after a brush fire destroys their aboveground parts.