Why are there no animals with three legs?

If "Why?" is the first question in science, "Why not?" must be a close second. Sometimes it's worth thinking about why something does not exist.

Don't be fooled: Flowers mislead traditional taxonomy

For hundreds of years, plant taxonomists have worked to understand how species are related. Until relatively recently, their only reliable source of information about these relationships was the plants' morphology—traits ...

Protein signal is crucial for accurate control of insect size

Two independent groups of researchers have identified a hormone that is responsible for keeping the growth and development of insects on track. The results, which are reported in the journal Science, suggest that Dilp8 provides ...

Lopsided fish show that symmetry is only skin deep

Putting function before form, members of the Perissodinus genus of fish have developed a hugely lopsided jaw that provides a distinct feeding advantage. Research published in the open access journal BMC Biology describes ...