Triploblasts played a crucial role in evolution, precisely because they did have internal organs, and in particular they could ingest food and excrete it. Their excreta became a major resource for other creatures; to get an interestingly complicated world, it is vitally important that shit happens.

T. Pratchett

*Triploblasts - organismi, kuriem embrioģenēzē attīstās 3 šūnu slāņi, no vidējā rodās iekšējie orgāni. Visi dzīvnieki, kas ir sarežģītāki pie medūzām, pieder pie triploblastiem.

It has even been "proved" that life is impossible because living systems become more and more ordered, whereas physics implies that all systems become more and more disordered. The main message that biologists have derived from these exercises has been a deep scepticism about the relevance of physics to biology, and a comfortable feeling of superiority, because life is clearly much more interesting than physics.

T. Pratchett. Science of Discworld