Journal Work for 2/27 and 2/28

Journal Work

Today’s class started out with answering questions on PAGE 10  of our journal. Here are the questions (there are two) and answers given by students:

Question 1: We can’t score more than a 98 on the Sunny Meadows game because….

  • No ecosystem is perfect. The foxes don’t eat the same amount of rabbits every time. The populations of the rabbits might go up and then the foxes eat more and they go down. There is always some kind of fluctuation.
  • There is no such thing as a perfect ecosystem.  Everything is always changing. You can’t keep life and death and what is eaten at a steady rate.
  • No ecosystem is perfectly stable.  Species need to be eaten or they die which means you can’t have the same population all the time. Nature is always changing so it isn’t always stable.
  • You can not have a perfect ecosystem without controlling it.  You can’t have an animal that eats the same thing everyday in the same portion.
  • An ecosystem can’t be perfect. This is because the foxes have to eat the rabbits so this population goes down, then the rabbits eat the grass, and populations change. So you can’t have all species staying the same number.
  • You can’t have a perfectly stable ecosystem. As predators eat their prey and more species are born, populations will fluctuate.


Question #2- How does the amount of biomass at each trophic levelcontribute (or help) to have a balanced ecosystem? (Think about it: What biomass do you need at each trophic level for an ecosystem to be balanced?)

  • The higher the trophic level, the less biomass. This is important because if there is too much biomass at the top, there wouldn’t be enough energy to support the population. This might cause the trophic level below it to die off. The grass (lowest level) might overpopulate.
  • You need a large base (a lot of biomass at the bottom), with a smaller middle, with the least amount of biomass being at the top trophic level.
  • There is more biomass at the bottom of the pyramid and less at each trophic level as you go up. This is because there is much less energy available to top predators so there are fewer. This tapering of the pyramid helps to keep balance in an ecosystem.
  • To have a balanced ecosystem there needs to be less biomass at each level as you go up the pyramid. You need to have a much bigger base to support all the organisms that come after it because energy is reduced as you go up.
  • For an ecosystem to be balanced, the biomass must be greater at the bottom and lesser at higher trophic levels. This is because consumers need to eat more producers to get enough energy to pass on to the next level.
  • The amount of biomass at each trophic level contributes to a balanced ecosystem when you have the right amount of biomass available for the next level.  You need the most at the producer level and less as you go up so species populations don’t get too big or too small at each level.



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