1. Explain how scientists define a biological species and describe the limitation of this definition.

2. List five types of prezygotic isolating mechanisms and explain how they prevent members of two different species from reproducing.

3. List three types of postzygotic isolating mechanisms and explain how they prevent members of two different species from reproducing.

4. Contrast allopatric speciation with sympatric speciation and explain how each method may result in the creation of a new species.

5. Explain how new species may arise by adaptive radiation.

1. Describe how the geological timescale is divided into eras, periods, and epochs.

2. Contrast the gradualistic model of evolution with the punctuated equilibrium model of evolution.

3. Explain some of the ways in which mass extinctions of organisms may have occurred.