Choose one of the three scenarios below to discuss. Write about what is causing this type of genetic variation and explain why you believe this (cite your evidence). 

Scenario #1  

In a population of spiders, there is a protein that is coded in the DNA to make venom.  In a particular spider, there was a protein variation due to a change in the genetic code.  This protein variation caused the spider’s venom to be stronger to kill its prey.  This genetic variation was passed down to offspring and was favored due to the amount of time shortened to eat its prey.

Scenario #2  
In a population of pigeons, there are genotypes for iridescent feathers and non iridescent feathers.  Over time, the females of the population would prefer mates with iridescent feathers 75% of the time.  Eventually, the phenotype of non iridescent feathers has decreased dramatically.

Scenario #3 
In a population of tropical fish, there are two types of genotypes that predict if the fish to survive better in cooler water.  Industry has created a pipeline that goes from the plant to the habitat of this fish.  In the pipeline was a cold water byproduct from cooling a machine.  Since the water has been added to the habitat, those with the recessive genotype have ended up dead.