Ch. 18 Population Genetics & Evolution, Cross Connection: The…
Cross Connection: The Gymnocalycium is a cactus with a phenotype that differs significantly from the ancestral conditions. All the critical genes involved in leaf production have mutated so much that they are nonfunctional. Genes involved in stem elongation now produce short stems and the species contains genes for succulence that were not present before.
Cross Connection: Artificial selection by crop breeders results in an increase frequency of certain alleles and the elimination of others. Cabbage, broccoli, and cauliflower are all the same species and they evolved from the same ancestor. Their evolution is controlled by artificial selection depending on the variety that farmers choose to grow.
Cross Connection: Severe heat and drought across Texas resulted in many wildfires across the whole state. In one town all trees were killed because they were not adapted to survive the fire. In another town, only a few trees were killed because genetically they differed, this is an example of survival of the fittest.