Life Cycle - Natural Environment (6B)
Pre Lab 

  • Adapting to the local environment. 
  • Exploring consequences of competition. 
  • adaptation
  • niche
  • worksheet

Students interpret a worksheet to observe organisms adaptation.  


There is much stress in communities, and it is this stress that continues to push better adapted species to be successful in the community.  There are many factors that govern competition between species which may result in extinction or separation of that species from its original areas.  Species are associated with a particular and unique set of biological and physical influences which are known as niches.  The term "niche" is used in ecology with a variety of meanings, but all of them have to do with a habitat that is filled by species within an entire ecosystem. 

Students will take a closer look at how populations can become stressed in an ecosystem by interpreting scientific data.  There are many chemical interactions between populations. It is known that there are many chemical secretions released by a particular plant population that will prevent other plants to grow around them.  A classic experiment deals with the California chaparral.  It had been known for many years that chaparral plants have a characteristic pungent and aromatic odor, and that this is due to the presence of volatile substances released from the shoots of the plants.  These chemicals (known as terpenes and phenolic compounds) are absorbed onto surrounding soil surfaces and in turn suppress the growth of the seedlings of many species in the area.

This chemical interaction may provide clues on  how ecosystems evolve through time.  Chemicals are used to prevent predators from attacking a plant.  Chemicals are emitted from plants and are used to protect the plants from their "enemies."  However, it is known that insects can develop mutants that can successfully attack these plants, and if a plant cannot develop a stronger plant, than it will go extinct because the insects will eat the plant into extinction.

  1. The worksheet asks students questions on what happens when there is competition between various populations.  This graph illustrates the "Rule of Gause."  If two species are utilizing the same resource, one will most probably reach this position where its growth rate is zero before the other.  The graph illustrates competition between two species population of Paramecium in a closed culture.  One species, Paramecium caudatum (B), declines to extinction as the result of its inability to compete with Paramecium aurelia (A) for the same food sources.  This exercise helps students to interpret data.  
  2. ANSWERS:  
    1.  time in days;  
    2.  population density (by volume);  
    3.  (2);  
    4.  (50);  
    5.  rapidly increases until about 9-10th day in which it levels off, decreases slightly after 18th day;  
    6.  increase at about same rate as A until the 4th day, then it slowly decreases until the population dies at 18;  
    7.  A and B are competing, B begins to lose on 4th day until it dies, A continues to survive.

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