1. Nutrition and Energy Flow Biology I

2. Lesson Objectives Describe the flow of energy through an ecosystem. Identify the ultimate energy source for photosynthetic producers. Describe food chains, food webs, and pyramid models.

3. Main Idea Autotrophs capture energy, making it available for all members of a food web.

4. How Organisms Obtain Energy Organisms differ in how they obtain energy. The ultimate source of energy is the sun, which supplies the energy that fuels life. All of the green plants and other organisms that produce their own food in an ecosystem are primary producers called autotrophs.

5. How Organisms Obtain Energy An autotroph is an organism that collects energy from sunlight or inorganic substances to produce food. –Ex. Grass, plants, some unicellular organisms Autotrophs are the foundation of all ecosystems because they make energy available for all other organisms in an ecosystem.

6. How Organisms Obtain Energy Heterotrophs are organisms that cannot make their own food and must feed on other organisms. Heterotrophs are also called consumers.

7. Types of Heterotrophs Herbivores feed on plants. Carnivores feed on other animals. Omnivores feed on both plants and animals. Detritivores eat fragments of dead matter in an ecosystem, return nutrients to the soil, air, and water where the nutrients can be reused by organisms. –Ex. Earthworms and crawfish

8. Types of Heterotrophs Scavengers are organisms that feed on already dead animals and play a crucial role in the ecosystem by eating the dead. –Ex. Hyenas and vultures Decomposers break down the complex compounds of dead and decaying plants and animals into simpler molecules that can be more easily absorbed. –Ex. Fungi, bacteria, and protozoa

9. Types of Heterotrophs Without the detritivores and decomposers the biosphere would be littered with dead organisms. Detritivores are especially important because they make the trapped nutrients in dead organisms available for all other organisms.

10. Models of Energy Flow Matter and energy flow through organisms in ecosystems. Each step in a food chain or food web is a trophic level. Nutrients and energy move from autotrophs to heterotrophs and eventually to decomposers.

11. Models of Energy Flow A food chain is a simple model that scientists use to show how matter and energy move through an ecosystem. Arrows are used to indicate the direction energy travels. –Ex. Algae  fish  heron

12. Models of Energy Flow Food chains can consist of three links but no more than five. Once the energy reaches the fifth level, there is only a small portion of the original amount of energy left

14. Models of Energy Flow Simple food chains are easy to study, but they cannot indicate the complex relationships that exist among organisms that feed on more than one species The model created is a food web and expresses all possible feeding relationships at each trophic level in a community.

15. Food Web Figure

16. Models for Energy Flow An ecological pyramid is also used to show how energy flows through an ecosystem. The higher trophic levels are layered on top of one another and at each level the energy transferred gets smaller and smaller. The first level is the sun-users (plants/autotrophs) and that continues upward to the top carnivores. Usually the amount of biomass (mass of living matter at each level) decreases at each trophic level.

17. Models of Energy Flow