system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How is it all breeds of dogs are the same species?

How is it that the tiny, white fluffy poodle is the same scientific species as the massive black great dane? Why is there is such a wide range of dog types and how can they all be considered the same species?
gpt
Because they can successfully interbreed.  A species is a group of individuals who can successfully interbreed with each other.  

There is a wide range of breeds because people keep breeding new breeds.  A lot of this is accomplished through inbreeding.  This is why a lot of breeds have a lot of genetic problems.