PACT Due Dates

Darwinian Dots Lab (Micah Hagan)

Darwinian Dots Lab (Micah Hagan)

7th Grade Life Science

53 minute period

Principle covered: Natural Selection as the mechanism for evolution.

Objective: Students will use variously patterned dots to simulate natural selection.  Students will interpret data to conclude whether certain traits are selected “for” or “against” in a given habitat.

California Standards covered:

Focus on Life Sciences

7.3.a  Students know both genetic variation and environmental factors are causes of evolution and diversity of organisms.

7.3.b  Students know the reasoning used by Charles Darwin in reaching his conclusion that natural selection is the mechanism of evolution.

Investigation and Experimentation -

7.7.c Communicate the logical connection among hypotheses, science concepts, tests conducted, data collected, and conclusions drawn from the scientific evidence.

Prior Knowledge:

Adaptations are characteristics which enable an organism to survive and reproduce in its environment.  Adaptations can be physical or behavioral.  What comprises a species?  Evolution is the process in which populations change over time.

Explanation –

Many different factors affect organisms on a day to day basis.  These can include environmental factors, predation, or competition among and between species.  Organisms with adaptations best suited to their environment are more likely to survive and reproduce; thus passing advantageous traits on to the next generation.   The process of natural selection affects how populations change over time and how various organisms behave in regard to obtaining resources and reproducing.

Materials

·         1 solid-colored (blue in this case) sheet of paper

·         1 patterned (blue) sheet of paper

·         50 solid paper dots

·         50 patterned paper dots

·         timer
  • Hole punch and student aid

 

Procedure
  1. Work in groups. One person will be the “predator” and the other will be the “scientist”.   Switch jobs for additional trials.
  2. The predator looks away while the scientist evenly spreads out all the dots (representing prey) on the sheet of solid-colored paper.
  3. When the scientist says “Go,” the predator quickly turns around, faces the “prey,” and removes as many solid-colored dots as possible in 10 seconds.
  4. Count the number of “prey” collected and record in Observations.
  5. Repeat Steps 2 - 4 two more times for a total of three trials.
  6. The predator again faces away while the scientist spreads out all the dots on the sheet of solid-colored paper.
  7. When the scientist says “go” the predator quickly turns around, faces the “prey,” and removes as many patterned dots as possible in 10 seconds.
  8. Count the number of “prey” collected and record in Observations.
  9. Repeat Steps 6 - 8 two more times for a total of three trials.
  10. Repeat Steps 3 - 10 using the patterned background.

Real world applications

1. Peppered moths in England – During the industrial revolution, darker colored moths became more common due to soot settling out of the atmosphere.  In the 1950’s, environmental controls were set in place and  there was a noticeable decline in darker colored moths in comparison to light colored moths.

2. Finches of the Galapagos – Perhaps one of Darwin’s most famous examples.  He noted that beak shape was related to what type of diet that specific finch specialized on.

3. Tortoise shell type (Another Galapagos example) -  Tortoises from various islands had shells adapted to allow for efficiency in feeding on the most advantageous foods.

4. The case for sickle cell -  While sickle cell or full blown anemia or not favorable conditions, in parts of the world where they are more common, there is a resistance to malaria, which is also a major problem of these areas.
 
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