 Purpose: In this investigation, we will find out how changes can occur in a population due to variation in traits.

 Traits in a population change over the course of several generations  Offspring grow up to look pretty much like their parents.  This is because the information for how to develop is passed from the parents to the offspring  Passing genetic information from one generation to the next generation is called inheritance.  You inherit alleles from your parents, Larkeys inherit alleles from their parents. This is true for all living organisms.

 The pioneering work on inheritance was done by an Augustinian monk named Gregor Mendel.  He spent years growing thousands of plants and animals, observing closely to see how similar they were to their parents.  His most important work was done with pea plants.  Mendel reasoned that the offspring must be inheriting something from each parent.

 Everything is made of cells.  This is where the information describing how to make you resides (is found)  Cells have many smaller structures inside, called organelles, which perform functions essential to life.

 ultimedia/PopulationsandEcosystems/pdfs/ transparencies/Pop_Eco_transp_22.pdf ultimedia/PopulationsandEcosystems/pdfs/ transparencies/Pop_Eco_transp_22.pdf

 DNA and chromosomes are found inside the nucleus.

 Found inside the nucleus of a cell  Also known as the inheritance messenger  DNA contains millions of atoms  In order to fit inside the nucleus, DNA is coiled and coiled again into structures called chromosomes.

 Chromosomes are the structures that carry the message of inheritance.  They come in almost identical pairs  They have specific active locations called alleles

 ultimedia/PopulationsandEcosystems/pdfs/ transparencies/Pop_Eco_transp_23.pdf ultimedia/PopulationsandEcosystems/pdfs/ transparencies/Pop_Eco_transp_23.pdf

 The drawing shows the nucleus of a cell from our make-believe animal, the Larkey.  There are 8 chromosomes  Chromosomes always come in pairs.  The Larkey has 4 pairs of chromosomes.  Both chromosomes in a pair have dark areas in exactly the same location. The dark areas are called alleles.  Two pairs of alleles working together make a gene

 The alleles are the code that determines the traits  The combination of alleles in an organism’s chromosomes is the organism’s genotype.  Two Alleles on paired chromosomes work together.  Together they are known as a gene  Alleles don’t all have equal influence in determining traits

 Dominant alleles are more influential in determining traits  They are represented by an uppercase letter  Recessive alleles are less influential in determining traits  They are represented by a lowercase letter

 AA or Aa = __________ legs  aa = __________ legs  EE or Ee = __________ eyes  ee = __________ eyes  FF = striped fur pattern  Ff = solid fur pattern  ff = spotted fur pattern  TT or Tt = __________ tail  tt = __________ tail

 ultimedia/PopulationsandEcosystems/pdfs/ transparencies/Pop_Eco_transp_26.pdf

 A gene is two alleles working together to control a trait  They determine eye color, hair color, fur patterns, etc.

 A Larkey has four features that we will focus on:  Legs (appendages)  Eye color  Fur pattern  Tail shape  Each feature is controlled by one gene.  Each of the four genes are located on a different chromosome

 ultimedia/PopulationsandEcosystems/pdfs/ transparencies/Pop_Eco_transp_25.pdf ultimedia/PopulationsandEcosystems/pdfs/ transparencies/Pop_Eco_transp_25.pdf

 ultimedia/PopulationsandEcosystems/pdfs/ transparencies/Pop_Eco_transp_20.pdf

 ultimedia/PopulationsandEcosystems/pdfs/ transparencies/Pop_Eco_transp_21.pdf ultimedia/PopulationsandEcosystems/pdfs/ transparencies/Pop_Eco_transp_21.pdf

 ultimedia/PopulationsandEcosystems/pdfs/ transparencies/Pop_Eco_transp_24.pdf ultimedia/PopulationsandEcosystems/pdfs/ transparencies/Pop_Eco_transp_24.pdf