Charles darwin observed a unique beak size and shape in the finch population of each of the galapagos islands that he visited. mc003-1.jpg which is the most likely cause of the observed variation? differences in the climate among the islands competition among individuals for available food sources competition among individuals for desirable mates differences in egg size among the populations

The answer is;   competition among individuals for available food sources

Due to competition among the finch birds, individual were forced to move to different islands that make up the Galapagos and develop a niche. The finches that became adapted to eating larger fruits developed larger beaks over time while those that eat small fruits retained smaller beaks.  

Louis Pasteur

Explanation:

Rejection of spontaneous generation is no longer controversial among biologists. By the middle of the 19th century, experiments by Louis Pasteur and others refuted the traditional theory of spontaneous generation and supported biogenesis.