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Food Chains Directions: Throughout this presentation, there

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Title: Food Chains Directions: Throughout this presentation, there


1
Food Chains
2
  • 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.

3
  • What is a Food Chain?

4
  • A food chain is a way to describe the feeding
    relationships between different organisms.

5
  • What is an organism?

6
  • An organism is a living creature, such as a plant
    or animal.

7
  • And what is a feeding relationship?

8
  • A feeding relationship describes who is eating
    what in a particular habitat.

9
  • Which organisms are able to use energy directly
    from the sun to make their own food?
  • Hint Can animals eat sunrays?

10
  • Plants can! Through the process of
    photosynthesis they use the energy from sunshine
    to make food.
  • That is why they are called primary producers.

11
  • What does produce mean?

12
  • All food chains start with green plants because
    they can produce food.

13
  • The next step up the food chain are the primary
    consumers.
  • These are animals that feed directly on plant
    material.

14
  • What does consume mean?

15
  • To consume is to eat, drink, use, or buy.

16
  • What are animals that eat plants called again?

17
  • Yep, herbivores.
  • Herbivores are primary consumers.

18
  • And who eats herbivores?

19
  • Carnivores, or animals that eat primary
    consumers, are called secondary consumers.

20
  • 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.

21
  • 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.

22
Who eats what in this food chain?
23
  • 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.

24
  • 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.

25
  • What does expended mean?

26
  • 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.

27
  • What is biomass?

28
  • Biomass is the weight of a living organism.

29
  • 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.

30
  • 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.

31
  • Which are there more of in Alaska, willows or
    wolves?

32
  • 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.

33
  • 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).

34
  • After 2 steps there is simply not enough
    available energy to support more than a few top
    predators.

35
  • What about animals that eat both plants and
    animals, such as bears and humans? What are they
    called?

36
  • Yes, they are called omnivores.

37
  • 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?!).

38
  • 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.

39
Who eats what in this aquatic food web?
40
Can you make a food web showing the feeding
relationships between the following arctic
organisms?
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