Lesson 4 - Natural Selection and Sex Selection

Lesson Objectives

Content Objective: Be able to explain how natural selection in finches on Daphne Major is an example of natural selection and the evidence to support this.

Language Objective: Be able to explain how finches on Daphne Major showed natural selection using the following statements as guidelines:

What is the struggle for existence (or how is the environment changing)?

What variations in phenotype and genotype existed?

Which phenotypes were better adapted?

What happened to the individuals’ number of offspring that were better adapted?

What happens to the allele frequency over time?

Syllabus Details:

D4.1.1—Natural selection as the mechanism driving evolutionary change - "Students should appreciate that natural selection operates continuously and over billions of years, resulting in the biodiversity of life on Earth."

D4.1.2—Roles of mutation and sexual reproduction in generating the variation on which natural selection acts - "Mutation generates new alleles and sexual reproduction generates new combinations of alleles.

D4.1.3—Overproduction of offspring and competition for resources as factors that promote natural
selection" - "Include examples of food and other resources that may limit carrying capacity."

D4.1.4—Abiotic factors as selection pressures - "Include examples of density-independent factors such as high or low temperatures that may affect survival of individuals in a population."

D4.1.5—Differences between individuals in adaptation, survival and reproduction as the basis for natural selection - "Students are required to study natural selection due to intraspecific competition, including the concept of fitness when discussing the survival value and reproductive potential of a genotype."

D4.1.6—Requirement that traits are heritable for evolutionary change to occur -"Students should understand that characteristics acquired during an individual’s life due to environmental factors are not encoded in the base sequence of genes and so are not heritable. Students are not required to know the term “Lamarckism” but it may be useful when discussing falsified theories about evolution by inheritance of acquired traits."

D4.1.7—Sexual selection as a selection pressure in animal species "Differences in physical and behavioural traits, which can be used as signs of overall fitness, can affect success in attracting a mate and so drive the evolution of an animal population. Illustrate this using suitable examples such as the evolution of the plumage of birds of paradise."

D4.1.8—Modelling of sexual and natural selection based on experimental control of selection pressures -"Students should interpret data from John Endler’s experiments with guppies."

Homework: See Homework Page