Flow of biological information

Phenotype: physical expression of genetic variation       Genotype: blueprint for the phenotype

• Phenotype is less variable than genotype
• Only genetic variation counts for evolution

The Genetic Basis of Variation

• Gene: A place on the chromosome that codes for a particular trait
• Allele: Polymorphism on the level of genes. Different version of the same genes that may result in a different phenotype
• Diploidy: There are two copies of each gene, one from the mother and one from the father
• Inherit two identical copies: homozygote
• Inherit two different copies: heterozygote

Nature vs Nurture

How To Separate Genes And Environment?

Example: Plant growing along an altitudinal gradient (see Campbell p. 437, fig. 23.8)

Common garden experiment: