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

Consumers  Heterotrophs : must acquire energy from other organisms by eating them.  Heterotrophs are also called consumers.

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 August 31, 2015 Homework 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

Food Webs  In most ecosystems, feeding relationships are much more 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 normal orientation. Pyramid of numbers is upside down.