<p>I think easy and hard are difficult to measure. One should be wary about tediousness vs difficulty. Taking determinants of 20 x 20 matrices by hand is very tedious, but not at all difficult (given enough time and patience). The concept is easy. I think Biology is placed under a similar guise. Sure, it takes you long time to memorize, that doesn’t mean the process itself is intellectually challenging. I’m sure to memorize 10,000 digits of pi would also take me quite a long time, but we’d both agree that it is not intellectually-challenging, right?</p>