How Many Species Have Mass M?

How many species have mass M?

Within large taxonomic assemblages, the number of species with adult body mass M is characterized by a broad but asymmetric distribution, with the largest mass being orders of magnitude larger than the typical mass. This canonical shape can be explained by cladogenetic diffusion that is bounded below by a hard limit on viable species mass and above by extinction risks that increase weakly with ...

How many species are there?

'How many species are there' is a question receiving more attention from biologists and reasons for this are suggested. Different methods of answering this question are examined and include: counting all species; extrapolations from known faunas and regions; extrapolations from samples; methods using ecological models; censusing taxonomists' views. Most of these methods indicate that global tot...

Perspective. How many women have osteoporosis?

Osteoporosis is widely viewed as a major public health concern, but the exact magnitude of the problem is uncertain and likely to depend on how the condition is defined. Noninvasive bone mineral measurements can be used to define a state of heightened fracture risk (osteopenia), or the ultimate clinical manifestation of fracture can be assessed (established osteoporosis). If bone mineral measur...

How many doctors should Sri Lanka have?

How many old people have ever lived?

BACKGROUND Uninformed generalizations about how many elderly people have ever lived, based on a poor understanding of demography, are found in a surprising number of important publications. OBJECTIVE We extend the methodology applied to the controversial question “how many people have ever been born?” initiated by Fucks, Winkler, and Keyfitz, to the proportion of people who have ever reached a ...