Chapter 18 Section 3 Energy Transfer

Producers Producers are autotrophs that are capable of converting chemical energy into organic molecules. Photosynthetic producers such as plants, protists and some bacteria convert solar energy into carbohydrates. Chemosynthetic producers such as bacteria and archaea convert inorganic, sulfur-based molecules into carbohydrates.

Producers The rate at which photosynthetic producers convert solar to organic energy is called gross primary productivity (GPP). The organic matter produced by autotrophs is called biomass. Only some of the energy stored as biomass is available to other organisms and some must be used by the producers.

Producers Net primary productivity (NPP) measures the rate at which biomass accumulates in an ecosystem. GPP is like a person’s monthly salary before taxes and NPP is like the actual amount in their actual paycheck. R= Respiration

Producers Net primary productivity varies greatly between ecosystems. Biomes that have high levels of light, temperature, nutrients and water have the highest NPP. Biomes like tropical rainforests and estuaries (river meets ocean) have a high diversity of producers that support other organisms.

Consumers Consumers are heterotrophs that cannot synthesize organic molecules from inorganic energy sources. Consumers either ingest (eat) or absorb nutrients from producers or other consumers. Decomposers are fungi or bacteria that break down producers and consumers after they die to make inorganic compounds available to the ecosystem again.

Consumers There are three levels of consumers that are based on what they eat. Primary (1°) consumers eat producers and can be either herbivores or omnivores. Secondary (2°) consumers eat primary consumers and can be either carnivores or omnivores. Tertiary (3°) consumers eat secondary consumers and are carnivores only. Quaternary (4°) consumers are also carnivores that are the top predators.

Consumers Detritivores can occur at any level because they consume dead organisms. They are scavengers that feed on detritus or waste products in addition to carcasses. They are different from decomposers because they do not break the parts down into simple compounds do not cycle nutrients back to the ecosystem

Energy Flow Trophic levels can be used to indicate an organisms position in a food chain and show the direction of energy transfer. All producers are in the first level, while all primary consumers are in the second level. The third and fourth levels contain secondary and tertiary consumers.

Energy Flow A food web is used to illustrate the many possible feeding relationships among the organisms in an ecosystem. The more organisms there are at each trophic level, the greater the stability of the ecosystem.

Energy Flow When one organism consumes another one, not all of the energy gets transferred as biomass. Things like undigestable bones or shells, or waste products such as shed skin or feces do not become part of the consumer. Most of the energy is lost as heat through the process of metabolism.

Energy Flow Only 10% of the energy in one trophic level is transferred to the next. A biomass pyramid is used to show the amount of organisms at each trophic level. Fewer consumers can be supported at each level because of the inefficiency of energy transfer.