Essential Knowledge 4.C.2

Environmental factors influence the expression of the genotype in an organism.

Environmental factors influence many traits both directly and indirectly. Examples include:

• Height and weight in humans
• Flower color based on soil pH
• Seasonal fur color in arctic animals
• Sex determination in reptiles
• Density of plant hairs as a function of herbivory
• Effect of adding lactose to a Lac + bacterial culture
• Effect of increased UV on melanin production in animals
• Presence of the opposite mating type on pheromones production in yeast and other fungi

An organism’s adaptation to the local environment reflects a flexible response of its genome. Examples include:

• Darker fur in cooler regions of the body in certain mammal species
• Alterations in timing of flowering due to climate changes

Students should be able to:

LO 4.23 construct explanations of the influence of environmental factors on the phenotype of an organism.

LO 4.24 predict the effects of a change in an environmental factor on the genotypic expression of the phenotype.