Final answer:
The shell length and seed number in peanuts contribute to natural selection in bird populations with variations in beak size, particularly during environmental stresses such as droughts. Studies like those of the Galápagos finches showcase how traits like beak size evolve in response to available food resources. Similarly, the survival and reproduction of garden pea seeds would be influenced by multiple environmental factors following natural selection.
Step-by-step explanation:
The shell length and seed number in peanuts can illustrate natural selection within a species during specific environmental conditions such as drought. When small seeds with thin shells become scarce, only birds with larger and broader beaks are able to feed on the large, tough seeds that remain. Assuming the drought persists and the bird population remains isolated, we can predict that natural selection would favor birds with certain traits, namely those with the larger and broader beaks suited to eat these seeds.
Over time, if birds with the larger beaks survive and reproduce more successfully than those with smaller beaks, the average beak size in the population would increase. This concept is supported by the well-documented studies by Peter and Rosemary Grant on the Galápagos finches, which demonstrated how beak size evolved in response to the availability of certain seed types after a period of drought. Similar processes could occur in a peanut-consuming bird population in response to changes in peanut seed characteristics.
For the handful of garden pea plant seeds scenario, natural selection would work in favor of the pea plants that can best capitalize on the available resources and conditions. Factors such as soil quality, water availability, sunlight, and predation could all create selection pressures that would affect survival and reproduction of the pea seeds. This would result in certain traits being favored over others, and over time, these traits would become more common in the population, demonstrating the principle of natural selection in shaping the genetic composition of the species.