Trophic Levels & The 10% Rule

Question 1

what is a continuous inflow of high quality energy used for in an ecosystem?

Answer 1

ecosystems depend on this continuous inflow to maintain their structure and function of transferring matter between the environment and organisms via biogeochemical cycles

Question 2

what are essential to life?

Answer 2

biogeochemical cycles

Question 3

which processes demonstrate the conservation of matter?

Answer 3

the biogeochemical cycles

Question 4

what is the flow of energy in terrestrial and near-surface marine communities?

Answer 4

energy flows from the sun to producers in the lowest trophic levels and then upward to higher trophic levels

Question 5

what is the 10% rule?

Answer 5

it approximates that in the transfer of energy from one trophic level to the next, only about 10% of the energy is passed on, the other 90% is used by the organism and lost as heat

Question 6

what explains the loss of energy that occurs when energy moves from lower to higher trophic levels?

Answer 6

the laws of thermodynamics

Question 7

what are the laws of conservation of matter/energy?

Answer 7

matter and energy are never created nor destroyed, they only change forms

Question 8

what is the 1st law of thermodynamics?

Answer 8

energy is neither created nor destroyed

Question 9

what demonstrates the conservation of energy?

Answer 9

food webs
when a rabbit eats a leaf, the energy from the leaf (glucose) is transferred to the rabbit and stored as body tissue like fat/muscle

Question 10

what is an example of the law of conservation of matter?

Answer 10

a tree dies and the nitrogen/carbon/water/phosphorus are returned to the soil and atmosphere

Question 11

what is an example of the law of conservation of energy?

Answer 11

sun rays (light energy) hit leaves and are converted into glucose (chemical energy)

Question 12

what is the second law of thermodynamics?

Answer 12

each time energy is transferred, some of it is lost as heat

Question 13

what is an example of the second law of thermodynamics?

Answer 13

in a coal-fired power plant, the potential energy in the bonds of the coal is released and converted into electricity; of which, only 35% is used to generate electricity and the other 65% is lost as heat

as the electricity is flowing down transmission wires, another 10% is lost

as you turn on a lightbulb, 95% of the energy is lost as heat and only 5% is coming though as actually light

Question 14

how does the second law of thermodynamics work in food webs?

Answer 14

the amount of useable energy decreases as you move up the food chain (organisms use up most of it for movement, development, etc.)

Question 15

what is an example of the second law of thermodynamics in a food chain?

Answer 15

the sun radiates 1000 joules of light energy
a plant only absorbs 1% (ecological efficiency) of this energy, so 10 J
a primary consumer eats the plant and absorbs 10% (10% rule) of this energy, so 1 J
a secondary consumers eats the animal before and absorbs 10% of this energy, so 0.1 J

the rest of the heat is lost to the environment

Question 16

what is a trophic pyramid? why is a pyramid shape used to represent this?

Answer 16

used to model how energy moves through an ecosystem
a pyramid shape is used because available energy decreases with each step up the food chain

Question 17

what are producers?

Answer 17

plants that convert sun’s light energy into chemical energy (glucose)

Question 18

what are primary consumers?

Answer 18

animals that eat plants (herbivores)

Question 19

what are secondary consumers?

Answer 19

animals that eat primary consumers or herbivores (carnivores and omnivores)

Question 20

what are tertiary consumers?

Answer 20

animals that eat secondary consumers or carnivores and omnivores (top/apex predators)

Question 21

the 10% rule doesn’t just apply to energy but also applies to:

Answer 21

biomass since energy is needed for growth and only 10% of energy transfers from one level to the next, only 10% of the biomass can be grown/supported (there can only be 1 kg of tertiary consumer biomass for every 1000 kg of producer biomass)

Question 22

what is biomass?

Answer 22

the total mass of all living things at a certain trophic level

Question 23

why are there more plants than large predators in an ecosystem?

Answer 23

because of the rule of 10
for every 1000 kg of producer biomass, only 100 kg of primary consumer biomass can be supported, only 10 kg of secondary consumer biomass can be supported, and only 1 kg of tertiary consumer biomass can be supported

Question 24

how do you calculate the biomass or energy available at the next level up in a trophic pyramid?

Answer 24

divide the lower level by 10 or move the decimal point to the left one place for each level