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.
Species Concepts and the Definition of Species. 1) Biological species concept: Species are groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups (Mayr, 1940).) Biological species concept: Species are groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups (Mayr, 1940).