3. mutualism
Encyclopædia Britannica, Inc.
Nature strikes the weirdest bargains, like the mutualistic arrangement between some species of termites and the protozoans that live in their guts. The protozoans get a home and a constant supply of wood chips. In exchange, the protozoans help the termites derive nutrition from cellulose in the wood. Termites even share their symbionts with other members of their colony, dispensing them in a sort of probiotic smoothie from their hind ends.
4. sexual selection
As gorgeous as it is, the male peacock’s tail is a ridiculous encumbrance. And that’s the point…by displaying his ability to survive while hauling around what is essentially a feathery Porsche, he demonstrates his fitness to potential mates. Despite what popular bromides would have you believe, it is, actually, the size of the wave in this case. This seeming deviation from the parsimony of evolution is called sexual selection.
