Why Members of the Same Species Look Different

Hey, I'm Lumi! Look at these three Lab puppies. They are all Labrador Retrievers — the same species — but do they look exactly alike? Nope! A *trait* is any feature of a living thing, like fur color, ear shape, body size, or eye color. Every member of a species shares the same *basic* set of traits — all Labs have four legs, floppy ears, and a wagging tail. But the exact details of those traits can be different from individual to individual. That difference is called *variation*. Where do variations come from? Two places! Some variations are passed down from parents — like a puppy's coat color. A puppy might get its black coat from mom and its big paws from dad. No two puppies get the exact same mix, so they end up looking a little different, even in the same litter! Other differences come from the environment. A puppy that eats more food might grow bigger than its brothers and sisters — not because of what its parents passed down, but because of what happened in its life. Today we are focusing mostly on the kind of variation that gets passed down from parents. Variation is not a mistake. It is one of the things that makes every individual special — and it means that no two members of a species are exactly the same.