Food Chain, Webs, and Pyramids

1. Food Chain, Webs, and Pyramids H. Biology

2. Relationship of Organisms • Organisms are resources / “food” for other organisms • Food is energy which allows the survival and reproduction of populations • Food chains and food webs show how energy is transferred from one organism to another

3. Energy Roles • The sun is the original source of all energy! • Producers: “Harness” energy from the sun • Ex. plants • Consumers: Organisms that eat something else • Ex. animals • Decomposers: return energy to the environment • Ex. fungus, bacteria

4. Vocab You Need to Know! • Producer - usually a green plant that produces its own food by photosynthesis • First-order Consumer - the organism that eats the producer • Second-order Consumer - the organism that eats or derives nutrients from the first-order consumer • Herbivore - a plant eater • Carnivore - an organism that obtains nutrients from the blood or flesh of an animal • Omnivore - an organism which eats both plant and animal matter • Scavenger - an consumer that eats dead animals (e.g. crab) • Detritivore - a consumer that obtains its nutrients from detritus • Decomposer - an organism such as bacteria and fungi that breaks down dead organisms and their wastes

5. Trophic Structure Ecosystems Ecosystems divided into trophic levels (feeding levels) Primary producers—autotrophs (mostly photosynthetic but can be chemosynthetic) Primary consumers—herbivores Secondary consumers—carnivores that eat herbivores Tertiary consumers—carnivores that eat other carnivores Detrivores/Decomposers—consumers that eat dead or decaying matter

6. Producers • Plants harness energy from the sunthrough photosynthesis • Producers are the base of every food chain • Meaning they are the source of food for all other animals

7. Consumers • 4 Types of Consumers: • Herbivore: Eat only plants • Ex. Cows, horses • Carnivore: Eat only meat • Ex. Polar bear • Omnivore: Eat plants and animals • Ex. Humans, grizzly bears • Scavenger: Carnivores that feed on bodies of dead organisms • Ex. Vultures

8. Decomposer • Decomposers break down waste and dead organisms and return the raw materials to the environment • Ex. Bacteria, fungi

9. Energy Flow through Biological Systems

10. Which Way Will the Energy Flow Go?! Grass ------ Cow ------ Human Plant ------ Mouse ------ Snake

11. Food Chain • Food Chain – series of organisms showing feeding relationships. • almost always begins with a green plant (producer) which is eaten by an animal (consumer). • The arrow means 'is eaten by', and points to the animal doing the eating! • This shows the flow of matter and energy along the food chain. • There are no decomposers in a food chain.

12. Food Web • Food Web is a network of interrelated food chains in a given area • Includes decomposers

14. Herring gull eggs 124 ppm Lake trout 4.83 ppm Concentration of PCBs Smelt 1.04 ppm Zooplankton 0.123 ppm Phytoplankton 0.025 ppm Toxins in the Environment • In some cases, harmful substances persist for long periods in an ecosystem • One reason toxins are harmful is that they become more concentrated in successive trophic levels • In biological magnification, toxins concentrate at higher trophic levels, where biomass is lower

15. Biomagnification What happens as levels of toxins (like DDT and mercury) as they move up trophic levels? • Toxin INCREASES in concentration from one link in a food chain to another • B/c they’re insoluble

16. Energy Pyramid • 2nd Law of Thermodynamics: 100% of the energy from one organism is NOT transferred to the next • Most of the energy (90%) is lost to the environment / used by the organism to carry out its life processes or it is lost to the environment • Energy Pyramid shows the amounts of energy that moves from one level to the next

17. Sample Energy Pyramid Pyramid of Net Productivity: ~10% of energy at each level converted to new biomass CALLED 10% rule (trophic efficiency) What happens as levels of toxins (like DDT) move up trophic levels? LOTS OF BIOMASS HERE Only 10% is passed on from one level to the next…the rest is LOST (usually as heat)