TROPHIC LEVELS AND 10% RULE

In-ground Pool For Crying out Loud Sit Ups

TROPHIC LEVELS AND 10% RULE Each level in a food chain or web is called a trophic (feeding) level. Trophic Levels: Primary Consumer: Herbivores or omnivores that consume the producers. Secondary Consumer: Omnivores and carnivores that consume primary consumers. Target: I will be able to identify the organisms who occupy each trophic level in a food web, and compare organisms in different trophic using the 10% rule. Pg. 33

Tertiary Consumer: Omnivores and carnivores that consume secondary consumers. Quaternary Consumer: Omnivores and carnivores that consume tertiary consumers.

Producer Primary consumer Secondary consumer Tertiary consumer

Producer Primary consumer Secondary consumer Tertiary consumer Quaternary consumer

Label the Producers, Primary, Secondary, Tertiary, and Quaternary Consumers.

10% Rule: Only about 10% of the energy available at one trophic level is transferred to organisms at the next trophic level.  The rest of the energy is used for life processes or lost to the environment as heat energy or waste at each level.

Pyramid of Energy: Shows that the energy available to organisms decreases with each trophic level.

Pyramid of Biomass: Shows that the total amount of biomass (total living tissue in all members of a population) decreases with each trophic level.

Pyramid of Numbers: Shows that the relative numbers of organisms decreases with each trophic level. Summary:

LIFE AND DEATH FOOD CHAIN DECISION You are living in Oklahoma with your family in 1934, during the worst drought in American history. You have 500 bushels of wheat and one milk cow (and nothing else to use for energy). What should you do to survive for the greatest length of time? A. Eat the cow and then eat the wheat. B. Drink the cows milk, eat the cow, and then eat the wheat. C. Don’t feed the cow, drink the cows milk, eat the cow when milk production stops and then eat the wheat. D. Feed the wheat to the cow and drink the milk E. Feed the wheat to the cow, drink the milk, and then eat the cow. F. Eat the wheat and then eat the cow.

THERE ARE 2 MAIN POINTS TO CONSIDER… If the cow is alive it is going through metabolism, converting organic molecules into waste products, ATP and heat. These energy conversions reduce the cows energy value to the people. Energy transfer from one trophic level to another to another is extremely inefficient. If the cow eats the wheat, then much of the energy from the wheat will be lost as heat and cow feces and will be unusable to the people

SOLUTION… A. Eat the cow and then eat the wheat. B.Drink the cows milk, eat the cow, and then eat the wheat. C.Don’t feed the cow, drink the cows milk, eat the cow when milk production stops and then eat the wheat. D. Feed the wheat to the cow and drink the milk E. Feed the wheat to the cow, drink the milk, and then eat the cow. F. Eat the wheat and then eat the cow. Choices D & E are not good because of the inefficiency of energy transfer between trophic levels

SOLUTION… A. Eat the cow and then eat the wheat. B.Drink the cows milk, eat the cow, and then eat the wheat. C.Don’t feed the cow, drink the cows milk, eat the cow when milk production stops and then eat the wheat. D. Feed the wheat to the cow and drink the milk E. Feed the wheat to the cow, drink the milk, and then eat the cow. F. Eat the wheat and then eat the cow. Choice F is not a good choice because it keeps the cow alive burning off calories.

SOLUTION… A. Eat the cow and then eat the wheat. B.Drink the cows milk, eat the cow, and then eat the wheat. C.Don’t feed the cow, drink the cows milk, eat the cow when milk production stops and then eat the wheat. The best choices are A & B. The best choices are A & B. Choice A allows for the consumption of the cows energy before much of it is wasted by the cows metabolism. Choice B is similar, but it allows for the harvesting of the energy in the cow’s milk. It may be a better choice than A if the cow is milked right away. But if the cow continues to produce milk over time (Choice C) it will waste energy in the process.

UNDERSTANDING ENERGY PYRAMIDS 1. Draw a Pyramid of Energy with 5 sections and label the trophic levels. (Producer, Primary Consumer…Quaternary Consumer) 2. Draw organisms in each level (as you would to show what eats what in that food chain). 3. Label the amount of energy being transferred on the side of each section. 4. Explain (at least 2 sentences) why only 10% is available to be passed onto the next trophic level using the 10% rule. *Use a minimum of 4 colors and good grammar. *Paste trophic level worksheets over the top so you can see your drawing below. Pg. 32