Every Rose

EVOLUTION QUESTION 1992:                                       L.PETERSON/AP BIOLOGY

               Evolution is one of the unifying concepts of modern biology.

  a.  Explain the mechanisms that lead to evolutionary change.

  b.  Describe how scientists use each of the following as evidence for evolution.

                               (1)   Bacterial resistance to antibiotics

                               (2)   Comparative biochemistry

                               (3)   The fossil record

Essay:

A.     Evolution is the changes that occur in a species over time.  These
changes can be caused by various modifications to the environment and also
inside the organism.  Punctuated Equilibrium causes a divide in a
population so that the gene pools are less diversified and two new species
will eventually occur.   In individual organisms mutations can occur in the
DNA which will change the genes of their offspring and eventually in the
species causing genetic variation.  

For example inside the species there can be large extinctions that cause a
decrease in the variety of the gene pool.  For example the bottleneck affect
is when a large scale natural disaster occurs and much of a population is
separated from the rest.  When this occurs only the genes carried by the
small amount of the species left are combined into a smaller gene pool.  
While the species continues to reproduce and evolve among themselves over
time this new population becomes less and less genetically related.  Species can also become less genetically related when they migrate to different areas.  This causes a gene flow that can cause either genetic addition or subtraction to a given population. 

Among the individual organisms changes occur during cell division (meiosis). When the DNA replicates, there is a time during Prophase 1 where the switching of nonsister chromatids occurs; crossing over.  After these mutations occur the mutations spread through the population by reproduction.  The only way that these genes would not spread is if the organisms with these same mutations were to inbreed and prevent the genes from spreading.  This process also causes and evolutionary change because if the group continues to reproduce only among them they will slowly become a new species.   

B.        - Bacterial Resistance to antibiotics is proof of evolution because it shows that mutations occurred in the bacteria overtime that made in resistant.  This is an example of natural selection occurring over time to create a cell that is resistant.

            -   The fossil Record is proof of evolution because it shows how ancient, extinct species were connected to species that are still around today.  It also shows similarities between species that wouldn’t seem to be related.  For example comparing the limbs of bats, cats, and dolphins, you can see that there are the same bone structures in all three, though they are different species.  It also shows that animals have become extinct over time, but there are other related species that lived on.