Transcription: Biologists talk about species, animals of a similar kind. Well, what's the definition of a species? Well, there isn't one really. Apart from small variations, members of a species are usually almost identical in how they're structured and how they behave. And members of the same species often look like each other. They can usually breed together too. So a spaniel and a Labrador dog look quite different, but they can breed together producing mongrel puppies. This is because in fact all dogs are one species. So how many different species are there in the world? Well, we just don't know. It could ...
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