1.11: Food Chains 1.11: Food Chains and Food Websand Food Webs

In order to understand how one organism can In order to understand how one organism can affect other organisms, ecologists use the idea affect other organisms, ecologists use the idea of food chains and food websof food chains and food webs

Food Chain –Food Chain – a feeding order in which each a feeding order in which each kind of organism kind of organism eats the one below iteats the one below it

Food ChainsFood Chains

Example of a Food ChainExample of a Food Chain

GrassGrass MouseMouse SnakeSnake FoxFox WolfWolf

Producer/Producer/AutotrophsAutotrophs

Primary Primary ConsumerConsumer

Secondary Secondary ConsumerConsumer

TertiaryTertiaryConsumerConsumer

QuaternaryQuaternaryConsumerConsumer

HerbivoreHerbivore CarnivoresCarnivores Top CarnivoreTop Carnivore(not eaten by any (not eaten by any other organism)other organism)

Scientists also use another naming method to Scientists also use another naming method to classify where organisms are on food chains classify where organisms are on food chains called trophic levelscalled trophic levels

Trophic Level –Trophic Level – a way of categorizing living a way of categorizing living things according to things according to how they gain their how they gain their energyenergy

Trophic LevelsTrophic Levels

Example of a Food ChainExample of a Food Chain

GrassGrass MouseMouse SnakeSnake FoxFox WolfWolf

Producer/Producer/AutotrophsAutotrophs

Primary Primary ConsumerConsumer

Secondary Secondary ConsumerConsumer

TertiaryTertiaryConsumerConsumer

QuaternaryQuaternaryConsumerConsumer

HerbivoreHerbivore CarnivoresCarnivoresTop CarnivoreTop Carnivore

(not eaten by any (not eaten by any other organism)other organism)

11stst Trophic Trophic LevelLevel

22ndnd Trophic Trophic LevelLevel

33rdrd Trophic Trophic LevelLevel

44thth Trophic Trophic LevelLevel

55thth Trophic Trophic LevelLevel

The producer/autotroph is always at the The producer/autotroph is always at the 11stst trophic level, the primary consumer is always at trophic level, the primary consumer is always at the the 22ndnd trophic level, the secondary consumer trophic level, the secondary consumer is always at the is always at the 33rdrd trophic level, and so on. trophic level, and so on.

The primary consumer eat The primary consumer eat autotrophsautotrophs, , secondary consumers eat the secondary consumers eat the primary primary consumersconsumers, and so on., and so on.

Some Things to Keep In Mind…Some Things to Keep In Mind…

Producer = Autotroph Producer = Autotroph (something that can (something that can produce its own food from sunlight or basic produce its own food from sunlight or basic nutrients)nutrients)

Consumer = Heterotroph Consumer = Heterotroph (something that has (something that has to get its food by eating other organisms)to get its food by eating other organisms)

Some Things to Keep In Mind…Some Things to Keep In Mind…

Label the Following Food Chains!Label the Following Food Chains!

rabbitrabbit

grassgrass

foxfox

shrubshrub

deerdeer

wolfwolf

producer/producer/autotrophautotroph

primary primary consumerconsumer

secondarysecondaryconsumerconsumer

producer/producer/autotrophautotroph

primary primary consumerconsumer

secondarysecondaryconsumerconsumer

11stst trophic trophic levellevel

22ndnd trophic trophic levellevel

33rdrd trophic trophic levellevel

11stst trophic trophic levellevel

22ndnd trophic trophic levellevel

33rdrd trophic trophic levellevel

Any Changes at One Level Affect All Any Changes at One Level Affect All Other Levels of a Food ChainOther Levels of a Food Chain

shrubshrub

deerdeer

wolfwolf

Hypothesize! If the number of deer Hypothesize! If the number of deer suddenly goes down, then:suddenly goes down, then:

1) The number of wolves will go down 1) The number of wolves will go down because they will have no foodbecause they will have no food

2) There will be more shrubs, since no 2) There will be more shrubs, since no deer are available to eat themdeer are available to eat them

In any one ecosystem, there can be many In any one ecosystem, there can be many types of producers, primary consumers, types of producers, primary consumers, secondary consumers, etc. Any individual secondary consumers, etc. Any individual organism is involved in many food chains.organism is involved in many food chains.

Food WebFood Web – – two or moretwo or more food chains inter- food chains inter-connectedconnected

Food WebsFood Webs

A Food WebA Food Web

rabbitrabbit

grassgrass

foxfox

shrubshrub

deerdeer

wolfwolf

grasshoppergrasshopper

grassgrass

1)1) True or False: There are 3 food chains in the food web True or False: There are 3 food chains in the food web False: There are many food chains in the food webFalse: There are many food chains in the food web

2)2) Which animal is the top carnivore in this food web?Which animal is the top carnivore in this food web? The wolfThe wolf

3)3) Which organisms are the primary consumers?Which organisms are the primary consumers? Grasshopper, rabbit, deerGrasshopper, rabbit, deer

4)4) On the web, which organism is on the 3On the web, which organism is on the 3rdrd trophic level in most of the food trophic level in most of the food chains, but on the 4chains, but on the 4thth trophic level on one of the food chains? trophic level on one of the food chains?

The wolf (it consumes the fox in one of the food chains)The wolf (it consumes the fox in one of the food chains)

Time to Think!Time to Think!

DecomposersDecomposers (organisms that break down (organisms that break down and feed on dead organisms) are usually not and feed on dead organisms) are usually not included on food chain diagramsincluded on food chain diagrams

Some organisms that are Some organisms that are omnivoresomnivores (eat both plants and animals) might be (eat both plants and animals) might be on a different trophic level depending on on a different trophic level depending on what food chain you are looking atwhat food chain you are looking at

One Last Thing…One Last Thing…

Cane Toad was introduced to Cane Toad was introduced to Australia in 1935 from Hawaii to Australia in 1935 from Hawaii to combat the Cane Beetle population combat the Cane Beetle population that was destroying their Sugar that was destroying their Sugar Cane crops. Cane crops.

Toads could not reach the beetles Toads could not reach the beetles which live high up on the sugar cane which live high up on the sugar cane

They started to eat everything small enough to fit in their They started to eat everything small enough to fit in their mouthsmouths

Case Study: The Cane ToadCase Study: The Cane Toad

There is no natural predator for the toad in AustraliaThere is no natural predator for the toad in Australia

They poison anything that tries to eat themThey poison anything that tries to eat them

The introduction of a species to control another species is The introduction of a species to control another species is called called biological controlbiological control. In every single case the outcome is . In every single case the outcome is never one we expectnever one we expect

Cane Toad

Case Study: The Cane ToadCase Study: The Cane Toad

Read Pg. 34-35Read Pg. 34-35 Do questions #1-7 (Pg. 39)Do questions #1-7 (Pg. 39)

Homework!Homework!