End Show Slide 1 of 41 Copyright Pearson Prentice Hall 3–2 Energy, Producers, and Consumers

End Show 3–2 Energy Flow Slide 2 of 41 Copyright Pearson Prentice Hall Producers Without a constant input of energy, living systems cannot function. Sunlight is the main energy source for life on Earth.

End Show 3–2 Energy Flow Slide 3 of 41 Copyright Pearson Prentice Hall Producers In a few ecosystems, some organisms obtain energy from a source other than sunlight. Some types of organisms rely on the energy stored in inorganic chemical compounds.

End Show 3–2 Energy Flow Slide 4 of 41 Copyright Pearson Prentice Hall Producers Only plants, some algae, and certain bacteria can capture energy from sunlight or chemicals and convert it into forms that living cells can use. These organisms are called autotrophs. Autotrophs use energy from the environment to produce “food” by assembling simple inorganic compounds into complex organic molecules. Autotrophs not only feed themselves but store energy and provide it to other organisms that eat them.

End Show 3–2 Energy Flow Slide 5 of 41 Copyright Pearson Prentice Hall Producers They are called primary producers because they are the first producers of energy-rich compounds that are later used by other organisms.

End Show 3–2 Energy Flow Slide 6 of 41 Copyright Pearson Prentice Hall Producers Energy From the Sun The best-known autotrophs harness solar energy through a process known as photosynthesis. During photosynthesis, these autotrophs use light energy to convert carbon dioxide and water into oxygen and energy-rich carbohydrates.

End Show 3–2 Energy Flow Slide 7 of 41 Copyright Pearson Prentice Hall Producers Photosynthesis is responsible for adding oxygen to— and removing carbon dioxide from—Earth's atmosphere.

End Show 3–2 Energy Flow Slide 8 of 41 Copyright Pearson Prentice Hall Producers Plants are the main autotrophs on land. Algae are the main autotrophs in freshwater ecosystems and in the upper layers of the ocean Photosynthetic bacteria are important in certain wet ecosystems such as tidal flats and salt marshes.

End Show 3–2 Energy Flow Slide 9 of 41 Copyright Pearson Prentice Hall Producers Life Without Light Some autotrophs can produce food in the absence of light. When organisms use chemical energy to produce carbohydrates, the process is called chemosynthesis.

End Show 3–2 Energy Flow Slide 10 of 41 Copyright Pearson Prentice Hall Producers

End Show 3–2 Energy Flow Slide 11 of 41 Copyright Pearson Prentice Hall Producers Chemosynthesis is performed by several types of bacteria. These bacteria represent a large proportion of living autotrophs. Some chemosynthetic bacteria live in very remote places on Earth, such as volcanic vents on the deep-ocean floor and hot springs. Others live in more common places, such as tidal marshes along the coast.

End Show 3–2 Energy Flow Slide 12 of 41 Copyright Pearson Prentice Hall Consumers Many organisms cannot harness energy directly from the physical environment. Organisms that rely on other organisms for their energy and nutrients are called heterotrophs. Heterotrophs are also called consumers.

End Show 3–2 Energy Flow Slide 13 of 41 Copyright Pearson Prentice Hall Consumers Consumers are classified by the ways in which they acquire energy and nutrients. Herbivores eat plants. Carnivores kill and eat other animals. Omnivores eat both plants and animals. Detritivores feed on plant and animal remains (detritus) and other dead matter. Types of Consumers

End Show 3–2 Energy Flow Slide 14 of 41 Scavengers are animals that consume the carcasses of other animals that have been killed by predators or have died of other causes. Decomposers, like bacteria and fungi, break down organic matter. Copyright Pearson Prentice Hall Types of Consumers (cont.)

End Show 3–2 Energy Flow Slide 15 of 41 Beyond Consumer Categories Categorizing consumers is important, but these simple categories often don’t express the real complexity of nature. For example, herbivores that eat different plant parts often differ greatly in the ways they obtain and digest their food. In addition, organisms in nature often do not stay inside the categories we put them in. For example, some carnivores will scavenge if they get the chance. Many aquatic animals eat a mixture of algae, bits of animal carcasses, and detritus particles.