Food Chains & Energy Flow

Food Chains & Energy Food Chains & Energy FlowFlow

Food Chains vs. Food WebsFood Chains vs. Food Webs

Food chainsFood chains show the path of food show the path of food from a producer to the final from a producer to the final consumerconsumer

Food websFood webs consist of consist of interconnected food chainsinterconnected food chains

Food ChainFood Chain

Food WebFood Web

•Primary consumers: (herbivores) feed directly on producers

•Secondary consumers: (carnivores) feed on primary consumers

•Tertiary consumers: feed on carnivores

Trophic LevelsTrophic Levels

Aquatic Aquatic EcosystemsEcosystems

Terrestrial Terrestrial EcosystemsEcosystems

Food ChainsFood Chains

Which are more Which are more numerous in an numerous in an ecosystem: ecosystem: producers or producers or consumers?consumers?

Producers are Producers are always more always more numerous than numerous than consumers, why?consumers, why?

Energy LossEnergy Loss Of the energy that an organism consumes, Of the energy that an organism consumes,

only a small fraction (only a small fraction (ecological ecological efficiencyefficiency of about 10%) is transferred to of about 10%) is transferred to the next trophic levelthe next trophic level

Where does that energy go?Where does that energy go? Most of the energy is lost as Most of the energy is lost as

heatheatThat’s hot.

Drop it Drop it like it’s like it’s

HOOOTTHOOOTT

““Rules” of Energy PyramidsRules” of Energy Pyramids

1.1. Not everything in the lower Not everything in the lower levels gets eaten levels gets eaten

2.2. Not everything that is eaten is Not everything that is eaten is digested digested

3.3. Energy is always being lost as Energy is always being lost as heatheat

House AnalogyHouse Analogy Just like how much Just like how much

of the energy used of the energy used to heat a house is to heat a house is wasted, much of wasted, much of the energy used by the energy used by organisms is organisms is wastedwasted

Efficiency ExampleEfficiency Example

Cars are only about 25% Cars are only about 25% efficientefficient Only 25% of the total Only 25% of the total

energy in gasoline is used energy in gasoline is used to make cars moveto make cars move

What happens to the other What happens to the other 75%???75%???

Energy EfficiencyEnergy Efficiency

Why is it more energy efficient to eat Why is it more energy efficient to eat grains directly, rather than the meat grains directly, rather than the meat of grain-eating animals? of grain-eating animals?

15 lbs. of feed

1 lb. of beef



6 lbs. of feed 1 lb. of pork



5 lbs. of feed 1 lb. of chicken


Why is it more energy efficient to eat Why is it more energy efficient to eat grains directly, rather than the meat grains directly, rather than the meat of grain-eating animals?of grain-eating animals?

2 lbs. of feed 1 lb. of fish

Summary QuestionSummary Question

Why do food chains rarely have more Why do food chains rarely have more than 4 or 5 trophic levels?than 4 or 5 trophic levels?

Primary ProductivityPrimary Productivity

Gross primary productivity (GPP): the rate at which an ecosystem's producers convert solar energy into chemical energy as biomass

Net primary productivity (NPP): the rate at which energy for use by consumers is stored in new biomass NPP = GPP – [rate producers use biomass]

Net Primary ProductivityNet Primary Productivity

The Food Chain RAPThe Food Chain RAP

From the From the SUN SUN ENERGY flowsENERGY flows Captured by Captured by plantsplants this energy goes this energy goes CHLOROPHYLLCHLOROPHYLL and WATER plus CO2and WATER plus CO2 Used in Used in PHOTOSYNTHESISPHOTOSYNTHESIS to manufacture food to manufacture food Plants get energy right from the sunPlants get energy right from the sun Making sugar for their food, a food chain has Making sugar for their food, a food chain has

begunbegun Plants are Plants are PRODUCERSPRODUCERS, the first link in the , the first link in the

chainchain Animals eat these plants for energy is obtainedAnimals eat these plants for energy is obtained

TheThe Food Chain RAP Food Chain RAP Some can’t make food these are Some can’t make food these are

CONSUMERSCONSUMERS They search for edibles this is no They search for edibles this is no

rumorrumor An animal like a mouse is the second An animal like a mouse is the second

shackleshackle It’ll eat only plants but animals it It’ll eat only plants but animals it

won’t tacklewon’t tackle


REFRAINREFRAIN OH OH OH PLEASE DON’T EAT ME!OH OH OH PLEASE DON’T EAT ME! OH OH OH PLEASE JUST LET ME BEOH OH OH PLEASE JUST LET ME BE OH OH OH I’LL BE REAL GOODOH OH OH I’LL BE REAL GOOD OH OH OH JUST DON’T MAKE ME OH OH OH JUST DON’T MAKE ME

FOODFOOD


Our mouse will nibble, on a plant as a treatOur mouse will nibble, on a plant as a treat Mice don’t make food, only plants do this featMice don’t make food, only plants do this feat Now this second link involves such a critterNow this second link involves such a critter Whose diet is plant material for lunch and dinnerWhose diet is plant material for lunch and dinner The next animal could include a snake The next animal could include a snake Snakes are PREDATORS that sit and lie and waitSnakes are PREDATORS that sit and lie and wait They’ll sit and stare with a watchful eyeThey’ll sit and stare with a watchful eye Until a mouse comes passing by…Until a mouse comes passing by…



FOODFOOD


Now you gotta be quick you can’t be lazy Now you gotta be quick you can’t be lazy or this food chain will drive you crazyor this food chain will drive you crazy You gotta be speedy you gotta be faster You gotta be speedy you gotta be faster to move too slow would be disasterto move too slow would be disaster The snake had to act to stay aliveThe snake had to act to stay alive And that’s a fact it ain’t no jiveAnd that’s a fact it ain’t no jive The snake will find food, and to its own The snake will find food, and to its own

dismaydismay Soon it too will become the PREY Soon it too will become the PREY


So the snake just feasted on the So the snake just feasted on the mouse mouse

The snake better be careful he better The snake better be careful he better look outlook out

Up in the air up in the skyUp in the air up in the sky A hungry hawk is soaring byA hungry hawk is soaring by



FOODFOOD


On the snake the hawk will swoopOn the snake the hawk will swoop After it eats the hawk will poopAfter it eats the hawk will poop Who will clean up all this mess?Who will clean up all this mess? Here come the Here come the DECOMPOSERSDECOMPOSERS at their best at their best If you’re a hawk you’ll eat a snakeIf you’re a hawk you’ll eat a snake A snake eats a mouse to stay in shapeA snake eats a mouse to stay in shape A mouse eats some seeds and some grainA mouse eats some seeds and some grain Put it together you have a FOOD CHAIN Put it together you have a FOOD CHAIN



FOODFOOD

Food Chains & Energy Flow

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