In the penultimate episode of Crash Course Zoology, we use everything we've learned so far to try and figure out what a "species" even is anyway! As you'll see, the incredible diversity of animals ...

Life depends on genes being switched on and off at exactly the right time. Even the simplest living organisms do this, but usually over short distances across the DNA sequence, with the on/off switch ...

Eat almost anything. Sleep almost anywhere. These, it seems, are the secrets to surviving in the city as a wild animal. Among the species that dominate urban spaces—pigeons, cockroaches, rats, ...