Food chains, webs and Pyramids

A ll living things (plant animals, bacteria, etc.) need energy to live, and all living things get this energy from food. Food, in itself, is NOT energy. It must be changed into energy by the organism using a process called respiration. The energy is used by the organism to carry out metabolic activity (all the things that cells do to keep you alive). The definition of a food chain is the transfer of energy from one organism to another. . The arrows point to the organism that receives the energy. These arrows are called strands. Producers are organisms that make their own food. Some, but not all, organisms make their own food using a process called photosynthesis. They use the sun's energy to combine carbon dioxide (CO2) and water into a food called glucose. Plants, algae and some types of bacteria (cyanobacteria) produce their own food this way. Producers also include certain types of bacteria that use chemical energy (instead of the sun) to make their own food. These bacteria live near underwater volcanoes that are so deep in the ocean that no sunlight can penetrate and they live in total darkness. But the volcanic vents put out chemicals that the bacteria can use to make their own food.

Food Pyramid

Consumers are organisms that obtain their food by consuming other organisms. Even though all organisms need food forenergy, many organisms do not have the adaptation ( to eat. Some organisms consume by absorbingfood (ex. fungi and bacteria) like a sponge absorbs water. Some organisms consume by eating with special adaptations calledmouths (and sometimes teeth or beaks). So all organisms that "eat" are consumers, but not all consumers "eat."

Organisms that consume producers are called primary consumers. Organisms that consume primary consumers are calledsecondary consumers. Organisms that consume secondary consumers are called tertiary consumers, while organisms thatconsume tertiary consumers are called quaternary consumers and so on.

Trophic level: The highest position an organism occupies on a food chain.

Decomposers: Decomposers are a special group of organisms that obtain their food by consuming dead or decayingorganisms and break them down into small molecules called "nutrients." Some of these nutrients enter the soil and are dissolvedin water where they can be taken up by plants through their roots. Decomposers can be fungi, bacteria, insects and smallanimals such as crabs.

Decomposers that don't have mouths to eat with, break down or digest dead organisms using special enzymes and then absorbthe nutrients (like a sponge absorbs water). Some examples of these decomposers include fungi and bacteria.

Decomposers can be primary, secondary, and tertiary consumers depending on which level of the trophic pyramid they areconsuming at. A worm that eats a dead plant is a primary consumer, while a fly maggot that eats a dead deer is a secondaryconsumer.

Organisms that eat....All organisms that eat are consumers, but not all consumers eat because they do not have special adaptations (such as mouths,teeth, beaks, etc.) to eat with. "Vore" means "to eat." We use special terms for organisms that eat.

Herbivores: Organisms that plants are called herbivores (herb = plant, vore = to eat) Cows and deer are herbivores, asare many insects. They are primary consumers (because they eat producers).

Carnivores: Organisms that eat other consumers are called carnivores (carne = meat, vore = to eat). Owls are carnivoresbecause they eat rodents and birds. Some insects are carnivores. If a carnivore eats an herbivore, it is also called a secondaryconsumer. Depending on what organism it eats, a carnivore may also be a secondary, tertiary, quaternary (and so on)consumer. Owls and shrews are both carnivores. Because the owl eats the shrew, this is an example of a tertiary consumereating a secondary consumer.

Omnivores: Organisms that eat both producers and consumers are called omnivores. People are omnivores, and so arerats, racoons, chickens & skunks. So... is an omnivore a primary, secondary or tertiary consumer? Well, it depends on what it'seating at the moment. If it's eating grass, it is a primary consumer. But when it's eating a rabbit, it's a secondary consumer. And when it eats a salmon (that eats insects and crustaceans), it's a tertiary consumer. But, we rank them at the level ofconsumption on average. So a deer will always be a primary consumer, and an owl can be as high as a 5th level consumer.

Detritivores: are a special kind of decomposer that eats dead or decaying organisms. Detritivores (detrit = wear down intobits, vore = to eat; have mouths and dead bits of plants and animals. All detritivores are decomposers because they bothconsume dead organisms. But not all decomposers are detritivores. Some examples include worms, crabs and certain insects(pill bugs, millipedes).

Scavengers, like decomposers, consume (and typically eat) dead organisms. But decomposers, scavengers consume large quantities and do not break down the food into small molecules called nutrients like decomposers do. Typical examples ofscavengers are racoons, vultures, polar bears, and hyenas.

: Each consumer in the food chain gets their energy in the form of food by consuming another organism - producers, which make their own food. When you draw a food chain, you then begin with a producer. Without the producers, there would be no food to pass onto the consumers. Don't forget, the arrows should point to the organism doing the consuming because the energy is transferredinto that organism. See the picture above for an example.

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(http://www.sheppardsoftware.com

/content/animals/kidscorner/games/foodchaingame.htm)Click on the image above to build food chains

(http://cf.ecokids.ca/pub/eco_info/topics/frogs/chain_reaction/play_chainreaction.cfm)

(http://www.sheppardsoftware.com

/content/animals/kidscorner/foodchain/producersconsumers.htm)Click on this image for another explanation of food chains.

Then go to the "Decomposer" game on the same website andsee if you can identify the decomposers.

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Use this food web to answer Question #9 above (and in yourGoogle Classroom document).

A food web is defined as " "

Because organisms in a habitat generally eat more than onething, the energy produced in plants connects with severalorganisms living together. For example, an owl eats manytypes of rodents, including rats, voles, shrews and birds. Since shrews eat insects, and rats and birds are omnivores,you can see that the food chains become interconnected andmore complex.

You can learn about energy transfer of the organisms indifferent habitats when you click on this link(http://www.harcourtschool.com/activity/food/food_menu.html)to order food webs in several habitats.

interconnecting food chains.

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BIOMASS  INFORMATION  

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TTrroopphhiicc PPyyrraammiidd This1. Each stage/level of the pyramid is called a "trophic level," or thehighest position an organism typically occupies in a food chain. Eachtrophic level is shared by organisms that occupy the same position in afood chain.

2. As you go up the trophic pyramid, the total number of organisms (orbiomass) at the next level decreases because the original energycaptured from the sun during photosynthesis is lost at each level of thetrophic pyramid (see explanation below)

3. The trophic pyramid shows that some, but not all, the original foodenergy made by photosynthesizers is transferred from one trophic levelto the next.

a. Organisms use food to obtain nutrients, grow and have energy for metabolic activity = all the things your cells do to help youlive. b. MOST (90%) of the food an organism makes (in the case of a producer) or consumes (in the case of a consumer) ischanged back into energy for metabolic activity through the process called "respiration." The remaining 10% of the food is usedto grow (or make biomass), SO the next organism that consumes it only receives 10% of the original energy. This is called the"10% rule."

For example, calories is a measure of food energy. A plant might make 10,000 calories of its own food by photosynthesis. Itwill use 9,000 (90% of 10,000 calories) calories to live and 1,000 to grow. When an grasshopper eats that plant, it will only get1,000 of the original calories that the plant made. That grasshopper will use 900 of those 1,000 calories for its own metabolism. If a frog eats that grasshopper, it will receive only 100 of those calories from the 1,000 that the grasshopper got.

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* Did you ever wonder what the 4th level is called? Quaternary!! What about the levels after that????5th: quinary6th: senary7th: septenary8th: octonary9th: nonary10th: denary

Because energy is lost as you go up the trophic pyramid, there are fewer numbers (less biomass) of consumers as yougo up the pyramid

On a trophic pyramid , we place the decomposers in aspecial place along the side of the pyramid (as seen in yourhomework and notes) because they are responsible forbreaking the dead organism down into small molecules callednutrients. Often these nutrients enter the soil and candissolve in water where they are then taken up by the roots ofplants, or they can be absorbed through the water by algaeand cyanobacteria.

We often refer to the top trophic level in a trophic pyramid asthe "apex consumer" or "top predator."