Final answer:
Small animals could survive the cataclysmic event due to their ability to find shelter, sustain on limited resources, and their nocturnal habits provided advantage during periods of reduced predation post-impact. Long tails in bipedal dinosaurs served as counterbalances for their long necks, aiding in stable and efficient movement.
Step-by-step explanation:
The likely reason small animals survived the cataclysmic impact of a large meteorite that led to the massive extinction at the Cretaceous-Paleogene (K-Pg) boundary is that their small size and diverse diets allowed them to find shelter and sustain themselves on limited resources. Additionally, small, burrowing animals or those that lived in water likely had protective habitats that shielded them from immediate effects of the impact such as intense heat and fires. The nocturnal habits of some small animals might also have played a role, as they were active during times when predation and competition were reduced in the chaotic aftermath.
As for dinosaurs being bipedal, having long tails would have helped balance their bodies, especially if they had long necks. The tail acted as a counterbalance, enabling bipedal dinosaurs to move efficiently and maintain stability while walking, running, or standing.