How could 1 asteroid wipe out only Dinosaurs?

Some species of prehistoric reptiles were ancestors of the alligator. Postosuchus was a reptilian that walked on four legs and had a skull that resembles a crocodilian. In fact, the postosuchus was a part of the rauisuchia family which is in the same evolutionary group (Pseudosuchia) as crocodilians. This particular dinosaur existed in the early parts of the Mesozoic Era during the Triassic. One animal that was more closely related to the crocodile was Sarcosuchus (appeared in the movie "Supercroc") which existed in the early parts of the Cretaceous period, the latter part of the Mesozoic Era. So, technically alligators/crocodiles are descended from certain species of dinosaurs. Frogs, I'm less educated on. There were certain prehistoric amphibians that were ancestors of the frog. Remember that the extinction event 65 million years ago wiped out 75%, not 100% of the species on the planet. Many mammals at the time were very small so were able to survive the harsh environments more so than the larger animals. So, you still have 25% of the species left which is plenty to continue the evolution of life on Earth. Birds are descendant from certain species of dinosaurs as well because they weren't all wiped out. Many of the descendants of dinosaurs from the Triassic period had evolved into the Cretaceous period so the descendants of earlier species of dinosaurs could have survived the extinction event....Show more

I've never really been all that into the asteroid theory, but ASSUMING that's what happened...

The asteroid was supposedly big enough to throw up clouds of dirt and dust that lingered in the atmosphere and blocked sunlight. This killed the plants, which in turn killed anything that ate plants, as well as the omnivores that ate the plant-eaters. I'm sure this wiped out most life on the planet, but living things are surprisingly adaptable. Something always survives.

Many of the creatures you mentioned don't actually need that much--sometimes any--light to survive. Many of the insects they eat don't need light to survive. The plants, not the creatures themselves, needed the light, and some plants don't actually need that much, either.

I have frogs that actually can't have regular light, and the plants I've put with them need only a few minutes of light a day to survive. IF the asteroid blocked the light, there probably would have been something similar that survived on small amounts of light or whatever light managed to filter through the dust. Once the dust cleared, eventually these would have evolved to take more light, or other forms of plant life would have come back....Show more

It didn't wipe out just dinosaurs, it wiped out a lot of species.
The ancestors of alligators, and all the creatures on Earth today, survived the extinction....Show more

It didn't just wipe out the dinosaurs: it was a major extinction event which also wiped out pleisosaurs and pterasaurs (neither of which are dinosaurs) along with most species of mammals and mammal-like reptiles along with most reptiles, amphibians and birds.

Countless invertebrates and plant species were also wiped out

The few survivors became the ancestors of all the species alive today...Show more

There was a mass extinction caused by the event. It killed more than dinosaurs, in fact it probably knocked out 3/4 of all plant and animal life....Show more