REMEMBER: YOU MUST Please finish notes HAND-WRITE YOUR on consumers NOTES!!! before taking Energy Flow Notes NOTES WILL BE DUE TOMORROW IN CLASS. Types of Consumers

1. Carnivores: kill and eat other animals.

2. Herbivores: obtain energy and nutrients by eating plant leaves, roots, seeds, or fruits.

3. Omnivores: diet includes both plant and animals.

4. Scavengers: consume the carcasses of dead animals.

5. Decomposers: “feed” by chemically breaking down organic matter.

6. Detritivores: feed on detritus particles. Beyond Consumer Categories

Categorizing consumers does not express the real complexity in nature.  Seeds and fruits are usually rich in energy and nutrients and easy to digest.  Leaves are generally poor in nutrients are usually difficult to digest.  Herbivores that eat leaves often differ greatly from animals that eat fruits and seeds. Energy Flow in Ecosystems Ecology Unit

THINK ABOUT IT • What happens to energy stored in body tissues when one organism eats another? That energy moves from the “eaten” to the “eater.” • You have learned that the flow of energy through an ecosystem always begins with photosynthetic or chemosynthetic primary producers. • Where it goes from there depends literally on who eats whom! Food Chains and Food Webs Key Question: How does energy flow through ecosystems?

 In every ecosystem, primary producers and consumers are linked through feeding relationships.  Energy flows through an ecosystem in a one-way stream, from primary producers to various consumers.

ENERGY Food Chains

 Definition: a series of steps in which organisms transfer energy by eating and being eaten.  Food chains may vary in length.  Short: Grass is eaten by rabbit, which is then eaten by a fox.  Long: Algae is eaten by herring; herring is eaten by cod; cod is eaten by a seal; and seals are eaten by orca whales.

 Primary Producers  Terrestrial food chains: plants  Aquatic food chains: phytoplankton and attached algae  In most ecosystems, feeding relationships are much more Food Webs complicated than those described in a simple chain.  One reason for this is that many animals eat more than one kind of food.  Example: On Africa’s Serengeti Plain, lions may prey upon gazelles, buffalos, and zebras.  Ecologists call this network of feeding interactions a food web.  Food Chains Within Food Webs  Each path you trace through a food web is a food chain.  A food web is a network that contains all the food chains in an ecosystem. Food Webs Decomposers and Detritivores in Food Webs

 Decomposers and detritivores are as important in most food webs as other consumers are.  Most producers die without being eaten.  In the detritus pathway, decomposers convert that dead material into detritus, which is eaten by detritivores.  The process of decomposition releases nutrients that can be used by primary producers.  Therefore, decomposers recycle nutrients in food webs! Analyzing Energy Flow Through Trophic Levels

 Each step in a food chain or food web is called a trophic level.  Primary producers make up the first trophic level.  Various consumers make occupy the other levels.  Ecological pyramids are models that show the relative amount of energy or matter contained within each trophic level in a given food chain or food web.  Pyramids of energy.  Pyramids of biomass.  Pyramids of numbers. Analyzing Energy Flow Through Trophic Levels Pyramids of Energy

 Theoretically, there is no limit to the number of trophic levels in a food web or the number or organisms that live on each level.  But… only a small portion of the energy that enters any trophic level is available to organisms at the next level.  Energy availability limits the size of food webs.  Organisms expend much of the energy they acquire on life processes, and most of the remaining energy is released into the environment as heat.  On average, only 10% of the energy available within one trophic level is transferred to the next level. Analyzing Energy Flow Through Trophic Levels Pyramids of Biomass and Numbers  The total amount of living tissue within a given trophic level is called its biomass.  Unit: grams per unit area  The amount of biomass a given trophic level can support is determined by the amount of energy available.  A pyramid of biomass is a model that illustrates the relative amount of living organic matter available at each trophic level in an ecosystem.  A pyramid of numbers is a model that shows the relative number of individual organisms at each trophic level in an ecosystem.  In most ecosystems, the pyramid of numbers is similar in shape to the pyramid of biomass.  The number of individuals on each level decrease from the level below. Analyzing Energy Flow Through Trophic Levels Pyramids of Biomass and Numbers: Special Case

 In some cases, consumers are much smaller in size and mass than the organisms they feed upon.  Example: countless caterpillars can feed off a few oak trees.  Oak trees have a large biomass.  Oak tree only represents one organism.  In such cases, the pyramid of numbers may be turned upside down, but the pyramid of biomass usually has the Pyramid of numbers is normal orientation. upside down.