Explain the processes by which the 1976 drought on Daphne Major produced directional selection on the medium?

ground finch.

Explain the processes by which the 1976 drought on Daphne Major produced directional selection on the medium?
Excerpt:





"The population of G. fortis on Daphne Major was an ideal subject for the study of the hazards of environmental fluctuations for small populations. The populations on Daphne Major are small and are mostly restricted to the island; therefore, all population parameters (birthrate, death rate, immigration rate, emigration rate) could be determined for the entire population that occupied the island. In addition, this finch population occupied habitats that have experienced no or little disturbance by humans. Therefore, this population presented the opportunity to study a small, isolated population under natural, fluctuating environmental conditions. Such study conditions are quite rare in today’s world."





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