How do we know that a golden retriever and a beagle are the same species even though they look so different?

Just by the way they look.

Explanation:

They have the same kind of bone structure, and the only real difference would be in size/shape of the bones, and the color of the fur.

clumped distribution, because you'de have all of the population gathered in a relatively small are.

it's the most common because it provides protection and a mate for reproduction

example: humans, seeweed, cattles, etc.

i think its through the fallopian tube