LS3+(9-11)+-+7

**Natural Selection/ evolution by…**
 * Students demonstrate an understanding of**

7a investigating __how information is passed from parents to offspring by encoded molecules__ (e.g. evidence from electrophoresis, DNA fingerprinting).

7b investigating __how the sorting and recombination of genes in sexual reproduction results in a great variety of possible gene combinations in the offspring of any two parents.__ (e.g. manipulate models to represent and predict genotypes and phenotypes, Punnett Squares, probability activities).

7c citing evidence of __how natural selection and its evolutionary consequences provide a scientific explanation for the diversity and unity of past and present life forms on Earth.__ (e.g. Galapagos Islands, Hawaiian Islands, Australia, geographic isolation, adaptive radiation).

What do these GSEs mean? What subtopics do students need to address to understand these GSEs?

 * Probability and Ratios- Students need to understand that probability is the chance of an event happening. In relation to genetics, the types of traits an offspring will possess depend on probability. A ratio is a comparison of two different occurences (i.e. 3/4 brown eyes: 1/4 blue eyes).
 * Traits- characteristics of an individual such as hair and eye color, height, or skin color.
 * Independent Assortment- The theory that alleles separate from each other during sexual reproduction to give an equal probability of offspring receiving a trait.
 * Monohybrid cross- cross between one trait from two different organisms
 * Dihybrid cross- cross between two traits from two different organisms
 * Punnet Squares- diagram used to predict the outcomes of a particular monohybrid, dihybrid, etc. genetic cross. A punnett square assumes independent assortment of the alleles or a particular trait.
 * Genotype vs. Phenotype- A genotype is the genetic makeup of an individual (i.e. Bb), while the phenotype is the actual trait characteristic (i.e. blue eyes)
 * Parent - Offspring Relationships
 * Trait Inheritance
 * Natural Selection and Evolution- Natural selection is the process by which traits become more or less common in a population depending on how the traits contribute to the survival of the organism. Evolution is the change of traits in a population over time.

What ideas to students need to understand before they can address the topics described above?

 * Students need to have a basic understanding of the following topics:
 * DNA and structure
 * Parent-offspring relationships
 * Sexual reproduction through meiosis

What misconceptions are students likely to have about these topics?

 * The following topics may cause student misconceptions:
 * Punnet squares and how to complete them
 * The difference between monohybrid and dihybrid.
 * The difference between phenotype vs. genotype.
 * Nature vs. Nurture in Natural Selection

What phenomena and representations help students understand these topics?

 * Mendel's Pea plant experiments- show the use of Punnett Squares and display how probability comes into play when crossing traits.
 * Modeling punnet squares
 * How the genotype is expressed in the phenotype.
 * Modeling evolution through natural selection using the Galapagos Islands as an evolutionary example.

Other resources related to this GSE:
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