Question

Is this a run on?

One group looks like a bear another is like a lion.

I am confused.

Answer 1

Yes. That's a run on sentence. Each of these should be a separate sentence:

One group looks like a bear.

Another is like a lion.

You could also join these two sentences with AND.

One group looks like a bear, and another is like a lion.

Answer 2

one group is a horse.
the next group is a dog.
join the sentenses and you get:
one group looks like a horse and the other looks like a dog.