Lesson 16 “Food Webs in Action”

Producers  Organisms that produce sugars inside their cells  Also called autotrophs  Provide a direct source of nourishment for all living things

Consumers  Organisms that rely on autotrophs for food  Also called heterotrophs  When they die they are eaten by scavengers such as crabs, lobsters and sharks

Scavengers  Break down materials and release wastes and other organic particles called detritus  Detritus sinks and is a major source of food for organisms living on the seafloor (benthic organisms)

Decomposers  Bacteria and fungi that break down dead organisms and convert them back into nutrients available to the ecosystem

Energy Flow: Food chains and food webs  Food chain- a way to picture how energy moves through a system from producer to consumer to decomposer in a pathway that has one direction  Energy flows from the sun to producers and finally to consumers

 Food web- many different food chains overlapping to form an intricate food web of different types of organisms within a community

Steps in a food chain  Tropic level- each step in a food chain  1 st level= producers  2 nd level= consumers that eat producers (primary consumers)  3 rd level= consumers that eat primary consumers (secondary consumers)  4 th level= predators that eat secondary consumers (tertiary consumers)

Energy transfer in a food chain  Not all energy within a trophic level is transferred to the next  10% rule- only 10% of energy is passed between trophic levels  Ex. If 10,000 calories are available to the primary consumer, then 1,000 would be available to the secondary consumer and only 100 calories would be available to the tertiary consumer…

Transferring Energy and Nutrients  Nearly all energy that fuels marine ecosystems comes from the sun.  Producers capture the sun’s energy and photosynthesize to create food (glucose)  Nutrients- chemicals necessary for metabolism  Glucose and nutrients combine to form complex sugars, proteins, etc.

Organic compounds  Nutrients that contain carbon and hydrogen  Examples:  1. proteins- contain nitrogen and help build an organism’s body strcutures

 2. carbohydrates- main source of energy for organisms (ex. glucose or starch)  3. lipids- provide energy and control the use of vitamins and chemical signals within the body (ex. lipids and fats)  4. Nucleic acids- transmit genetic information and direct protein synthesis (ex. DNA & RNA)

 5. vitamins- organic substances necessary in very small amounts for carrying out metabolic processes (ex. Vitamin A, vitamin C and D)  6. minerals- inorganic substances required in very small amounts for nerve signal transmission in animals (ex. iron, zinc, sodium)

Cellular respiration  Organisms must break down food molecules in order to release the energy stores within them

Nutrient cycling  Biogeochemical process of passing elements (C, H, O, N, S and P) and the compounds they form within the Earth system