Food Chains

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Food Chains
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• Directions Throughout this presentation, there
  will be slides with a blue background (like this
  one) and a question. If you know the answer to
  this question, raise your hand.
• Your teacher will try to decide who raised their
  hand first.
• If you get it right, your group gains one point.
  If you dont know and you make an educated guess,
  then your group gets 1/2 a point. If you make an
  uneducated guess, meaning you are completely and
  utterly wrong, then you get no points.
• Fill out the handout with the appropriate answers
  and definitions as we go along.

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• What is a Food Chain?

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• A food chain is a way to describe the feeding
  relationships between different organisms.

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• What is an organism?

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• An organism is a living creature, such as a plant
  or animal.

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• And what is a feeding relationship?

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• A feeding relationship describes who is eating
  what in a particular habitat.

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• Which organisms are able to use energy directly
  from the sun to make their own food?
• Hint Can animals eat sunrays?

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• Plants can! Through the process of
  photosynthesis they use the energy from sunshine
  to make food.
• That is why they are called primary producers.

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• What does produce mean?

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• All food chains start with green plants because
  they can produce food.

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• The next step up the food chain are the primary
  consumers.
• These are animals that feed directly on plant
  material.

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• What does consume mean?

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• To consume is to eat, drink, use, or buy.

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• What are animals that eat plants called again?

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• Yep, herbivores.
• Herbivores are primary consumers.

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• And who eats herbivores?

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• Carnivores, or animals that eat primary
  consumers, are called secondary consumers.

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• So a food chain shows who eats what in a
  particular habitat.
• For example, a piece of willow is eaten by a
  moose, which is then eaten by a wolf.

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• The arrows between each item in the chain always
  point in the direction of energy flow- in other
  words, from the food to the feeder.

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Who eats what in this food chain?
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• All food ultimately comes from green plants or
  producers.
• The other organisms in the food chain are
  consumers, because they all get their energy and
  biomass by consuming (eating) other organisms.

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• All food chains are pretty short.
• There are never more than four steps, because a
  lot of energy is lost at each step, and after
  three steps most of the available energy has been
  expended.

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• What does expended mean?

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• Energy transfer up the food chain is inefficient.
  That means that a lot of it is lost at each
  step.
• Only 10 of the biomass consumed by an organism
  actually becomes biomass of the consumer.

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• What is biomass?

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• Biomass is the weight of a living organism.

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• If a wolf eats 10 pounds of musk oxen meat in one
  day, how much of that meat will become wolf
  biomass?
• Hint Remember the 10 efficiency rule.

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• If a wolf eats 10 pounds of musk oxen meat in one
  day, it will only gain 1 pound.
• The rest of the energy is lost.

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• Which are there more of in Alaska, willows or
  wolves?

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• There are a lot more willows than there are
  wolves.
• Due to the energy loss at each transfer up the
  food chain, there are a lot more organisms lower
  in the food chain than up at top.

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• This also explains why the organisms at the top
  of food chains (such as wolves) are very small in
  number compared to those lower down (such as
  willows).

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• After 2 steps there is simply not enough
  available energy to support more than a few top
  predators.

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• What about animals that eat both plants and
  animals, such as bears and humans? What are they
  called?

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• Yes, they are called omnivores.

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• Even animals that arent omnivores do not usually
  only eat one particular organism (can you imagine
  eating only one food, like carrots, for example,
  and nothing else?!).

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• Because animals eat more than one type of food, a
  better way to show feeding relationships is to
  draw a series of interconnecting food chains,
  called a food web.

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Who eats what in this aquatic food web?
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Can you make a food web showing the feeding
relationships between the following arctic
organisms?