Food Chains & Food Webs

I. Food Chain A) not a cycle!! B) tracks flow of energy through an ecosystem C) some energy is lost as heat every time it is transferred from one organism to another D) only about 10% of the energy passed on becomes stored in the body of the consumer E) chains are straight lines showing only ONE possible path for the energy flow F) arrows point to where energy is going.

II. Food Web A. Interconnected path of energy through an ecosystem B. shows all possible paths that energy could take

III. Earth = Open System to E A. Open systems allow things to come in and leave. B. Energy comes into Earth as solar radiation and leaves as heat radiation (I-R) C. Energy is not recycled like N, P, C because the earth is a closed system for elements

IV. First step in all food chains A) Autotrophs : 1) self feeders 2) use energy from the sun or chemicals a) photosynthetic b) chemosynthetic 3) also called producers

V. Consumers A. Heterotrophs 1) other feeders: feed on other organisms 2) classified by how many steps down the chain they are. a) primary consumer = eats plant b) secondary consumer = eats animal c) tertiary consumer = eats animal that has eaten another animal

B. Types of Heterotrophs 1. Herbivores – eat plants or algae 2. Carnivores – eat other heterotrophs 3. Omnivores – eat both plants & animals 4. Detritivores – animals that eat detritus 5. Scavangers – animals that eat organisms that they find dead (don’t kill own food) 6. Decomposers – consume dead organic matter includes bacteria, fungi & animals

VI. Pyramid of Energy A. shows how much energy is on each trophic level. (feeding level) B. Used for food chains or food webs C. 90% of energy is lost/used or converted to heat between each level

VI. Pyramid of Numbers A) Shows number of organisms at each level of a food chain. B) Amount of energy at each level limits the number of individuals at that level.

VII. Pyramid of Biomass A. Biomass = mass of living matter B. takes into account size of individuals

VIII. Biological Magnification A) Toxins become more concentrated (magnified) as they are passed up food chain B) Toxins absorbed by fat/oils in bodies 1) herbicides 2) pesticides (DDT) 3) industrial chemicals (PCB, PBB, Dioxin) 4) pollution Mercury

C. DDT Pesticide used against mosquitoes 1. washes into water 2. absorbed by producers 4. soft egg shells 5. killed raptors and other birds at top of food chain 6. estrogen mimic poss. Human impact

D. Mercury 1. released by burning coal 2. rains into water 3. biomagnified in fish 4. brain damage in humans