Chapter 3 Section 2: Energy Flow

•Identify the source of energy for life processes•Trace the flow of energy through living systems•Evaluate the efficiency of energy transfer among organisms in an ecosystem.

Producers• Sunlight is the ultimate source of energy for most life on Earth.

(this is from less than 3% of the sunlight that actually reaches the Earth)

• Some types of organisms rely on the energy stored in inorganic chemical compounds.

• All organisms that use energy from their environment to fuel the assembly of simple inorganic compounds into complex organic compounds are called autotrophs.

• Because they make their own food, they are also called producers.

• They are essential to the flow of energy through the biosphere.

Types of ProducersEnergy from the Sun• These are the best known

types.• They harness energy from the

sun in a process called photosynthesis.

• During photosynthesis, light energy is used to power chemical reactions that convert carbon dioxide and water into oxygen and sugars and starches.

Life without Light• These are lesser known, but

make up a larger percentage of the producers on Earth.

• They harness energy from the chemical bonds of inorganic molecules such as hydrogen sulfide in a process called chemosynthesis.

• Examples include bacteria that live in extreme environments like volcanic vents and hot springs.

Types of Consumers• Many organisms (animals, fungi, and many

bacteria) can not make their own food and must acquire energy from other organisms.

• These organisms are called heterotrophs or consumers.

• There are many types of heterotrophs

Herbivores•Obtain energy by eating only plants•Examples include cows, caterpillars, and deer

Carnivores•Obtain energy from eating animals•Examples include snakes, dogs, and owls

Omnivores•Obtain energy from eating plants and animals•Examples include humans, bears, and crows

Detritivores•Obtain energy from feeding on plant and animal remains and other dead matter•Examples include mites, earthworms, snails, and crabs

Decomposers•Obtain energy by breaking down organic matter•Examples include bacteria and fungi

Food Chains• A food chain is a series of steps in which organisms transfer

energy by eating and being eaten.• The energy in a food chain flows from the sun or inorganic

compound to autotrophs and then to heterotrophs.

Food Webs•A food web links all the food chains in an ecosystem together•The energy in a food web flows from the sun or inorganic compound to autotrophs and then to heterotrophs.

Trophic Levels•Each step in a food chain or food web.•Producers make up the first trophic level•Consumers make up the second, third, or higher trophic level.•Each consumer depends on the trophic level below it for energy.

Ecological Pyramids:Energy Pyramid

Only about 10 percent of the energy available within one trophic level is transferred to organisms at the next trophic level.

Ecological Pyramids:Biomass Pyramid

A biomass pyramid represents the amount of potential food available for each trophic level in an ecosystem

Ecological Pyramids:Pyramid of Numbers•An ecological pyramid which is used to represent the number of individual organisms at each trophic level.•A pyramid of numbers isn’t always necessarily a “pyramid” because you might have fewer individual producers than you have herbivore consumers.