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A landlocked country is a country that does not have any territory connected to an ocean or whose coastlines lie solely on endorheic basins.Currently, there are 44 landlocked countries, two of them doubly landlocked (Liechtenstein and Uzbekistan), and three landlocked de facto states in the world.
This glossary of biology terms is a list of definitions of fundamental terms and concepts used in biology, the study of life and of living organisms.It is intended as introductory material for novices; for more specific and technical definitions from sub-disciplines and related fields, see Glossary of cell biology, Glossary of genetics, Glossary of evolutionary biology, Glossary of ecology ...
A clade is by definition monophyletic, meaning that it contains one ancestor which can be an organism, a population, or a species and all its descendants. [ note 1 ] [ 10 ] [ 11 ] The ancestor can be known or unknown; any and all members of a clade can be extant or extinct.
In biology, two related species or populations are considered sympatric when they exist in the same geographic area and thus frequently encounter one another. [1] An initially interbreeding population that splits into two or more distinct species sharing a common range exemplifies sympatric speciation .
The term sister group is used in phylogenetic analysis, however, only groups identified in the analysis are labeled as "sister groups".. An example is birds, whose commonly cited living sister group is the crocodiles, but that is true only when discussing extant organisms; [3] [4] when other, extinct groups are considered, the relationship between birds and crocodiles appears distant.
A hybrid zone may appear during secondary contact, meaning there would be an area where the two populations cohabitate and produce hybrids, often arranged in a cline. The width of the zone may vary from tens of meters to several hundred kilometers. A hybrid zone may be stable, or it may not.
In the DNA segment shown, the 5′ to 3′ directions are down the left strand and up the right strand. The 5′-end (pronounced "five prime end") designates the end of the DNA or RNA strand that has the fifth carbon in the sugar-ring of the deoxyribose or ribose at its terminus.
In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each other, further blurring any distinctions.