Leap seconds keep UTC within 0.9 seconds of UT1. In the 44 years up to and including 2015, a total of 26 leap seconds have been added; the most recent was added on 30 June 2015. If high precision is not required, the general term Universal Time (UT) may be used.
A species is often defined as the largest group of organisms where two hybrids are capable of reproducing fertile offspring, typically using sexual reproduction. While in many cases this definition is adequate, the difficulty of defining species is known as the species problem.ractically, biologists define species as populations of organisms that have a high level of genetic similarity. This may reflect an adaptation to the same niche, and the transfer of genetic material from one individual to others, through a variety of possible means.
In biology, a species (abbreviated sp. , with the plural form species abbreviated spp. ) is one of the basic units of biological classification and a taxonomic rank. usable definition of the word species and reliable methods of identifying particular species are essential for stating and testing biological theories and for measuring biodiversity, though other taxonomic levels such as families may be considered in broad-scale studies.