Some animals, such as a cat and a dog, have many similarities.  Others, such as a fish and a bird, have fewer similarities.  What is TRUE about the ancestors of these animals?

  1. Cats and dogs share a common ancestor with each other, but fish and birds do not share a common ancestor with each other.
  2. Cats and dogs share a common ancestor with each other, and fish and birds share a common ancestor with each other, but cats and dogs do not share a common ancestor with fish and birds.
  3. Because cats, dogs, fish, and birds are separate species, none of them shares a common ancestor with any other.
  4. Cats, dogs, fish, and birds all share an ancient common ancestor.