Topic 5.2: Natural Selection

Essential Idea:   The diversity of life has evolved and continues to evolve by natural selection.
At SHS, Topic 5.2 is taught in the following class unit(s):

Statements & Objectives:

5.2.U1  Natural selection can only occur if there is variation among members of the same species.
  • Define variation.
  • Explain why natural selection can only function if there is variation in a species.
5.2.U2  Mutation, meiosis and sexual reproduction cause variation between individuals in a species.
  • List sources of genetic variation.
5.2.U3  Adaptations are characteristics that make an individual suited to its environment and way of life.
  • Define adaptation.
  • List examples of adaptations.
5.2.U4  Species tend to produce more offspring than the environment can support.​
  • Use an example to illustrate the potential for overproduction of offspring in a population.​
  • State that species have the ability to produce more offspring than the environment can support.
5.2.U5  Individuals that are better adapted tend to survive and produce more offspring while the less well adapted tend to die or produce fewer offspring.​
  • Outline how a “selective pressure” acts on the variation in a population.
  • List examples of “selective pressures.”
  • Explain the effect of the selective pressure on the more and less adapted individuals in a population.
5.2.U6  Individuals that reproduce pass on characteristics to their offspring.​
  • Contrast acquired characteristics with inheritable characteristics.
  • State that only inherited characteristics can be acted upon by natural selection.
5.2.U7  Natural selection increases the frequency of characteristics that make individuals better adapted and decreases the frequency of other characteristics leading to changes within the species.
  • Compare the reproductive success of better and less well adapted individuals in a population.
  • Explain the cause of the change in frequency of traits in a population through natural selection.​. ​
5.2.A1  Changes in beaks of finches on Daphne Major.
  • Outline the role of Charles Darwin and Peter and Rosemary Grant in the study of Galapagos finches.
  • Explain how natural selection leads to changes in the beaks of Galapagos finches with changes in weather conditions. ​
5.2.A2  Evolution of antibiotic resistance in bacteria.
  • Explain how natural selection leads to changes in antibiotic resistance.
  • List reasons why evolution of antibiotic resistance has been rapid.
  • Outline the effect of not completing a full dose of antibiotics on the development of antibiotic resistance.​ ​
5.2.NOS  Use theories to explain natural phenomena- the theory of evolution by natural selection can explain the development of antibiotic resistance in bacteria.​
  • List three trends that have been observed in the development of antibiotic resistance.
  • Use a graph to illustrate antibiotic resistance over time.​

In the News:
"When we try to pick out anything by itself, we find it hitched to everything else in the Universe." 
 John Muir,   1911