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Education
Natural Selection
 

Learning Objectives

At the end of this lab, students should know...

What is fitness?

Fitness is the reproductive success of organisms relative to others.

What is selection?

Selection is one of the main mechanisms of evolution. It acts on heritable traits, enabling organisms with phenotypes that favor survival to produce more offspring than others with less favorable phenotypes.

What are the survival and reproduction rates?

Survival rate of a phenotype is the percentage of individuals with that phenotype to survive to reproductive age. Reproduction rate of a phenotype is the number of offspring generated by an average individual of that phenotype.

How do we calculate fitness and selection? How do fitness and selection relate to each other?

Relative fitness is the product of survival and reproduction rates of a phenotype divided by the value of the population’s most successful phenotype. Strength of selection for a phenotype depends on its relative fitness, since selection coefficient can be calculated by subtracting relative fitness value of a phenotype from 1.

What are the main types of selection and how do they differ?

Main types of selection are directional, disruptive, and stabilizing. Directional selection favors extreme values of a trait in one direction. Disruptive selection favors two extremes of a phenotype in opposing directions. Stabilizing selection favors an optimum value.

List of Materials

  • Dissecting Trays
    5
  • White colored construction Paper
    5
  • Black colored construction Paper
    5
  • Scissors
    5
  • Print out Table 2-5 (1 set/each group)
    5 sets
  • Tape
    1 /station
  • Pipe Cleaners (12 inches each) - (6 white, 6 black, 13 gray, 62 any colored/station)
    Dependent on the lab size

Lab Prep

  1. Simulating Natural Selection
    • To prepare for the lab, set out workstations for each student pair containing 6 white, 6 black, and 13 gray 12 inch pipe cleaners.
    • Then, add 62 pipe cleaners in any color but black, white or gray, a roll of tape, and a pair of scissors.
    • Also, place one piece of black construction paper and one piece of white construction paper at each station.
    • Finally, print out tables so that there are enough for each set of partners in the class.
    • To save materials for subsequent labs, inform students to save the materials and to avoid damaging them as much as possible.

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