Species

A species () is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. It can be defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. Other ways of defining species include their karyotype, DNA sequence, morphology, behaviour, or ecological niche. In addition, palaeontologists use the concept of the chronospecies since fossil reproduction cannot be examined. The most recent rigorous estimate for the total number of species

thumb|An example of the biodiversity of fungi in a forest in North Saskatchewan (in this photo, there are also leaf [[lichens and mosses).]]

series of neighboring populations, each of which can interbreed with closely sited populations, but for which the 2 end populations in the series are too distantly related to interbreed, despite potential gene flow between each linked population

Bioaccumulation is the gradual accumulation of substances, such as pesticides or other chemicals, in an organism. Bioaccumulation occurs when an organism absorbs a substance faster than it can be lost or eliminated by catabolism and excretion. Thus, the longer the biological half-life of a toxic substance, the greater the risk of chronic poisoning, even if environmental levels of the toxin are not very high. Bioaccumulation, for example in fish, can be predicted by models. Hypothesis for molecular size cutoff criteria for use as bioaccumulation potential indicators are not supported by data. B

informal grouping of taxa

formal description of a new taxon

gradual variation of the characteristics of a species along its territory

concept in conservation biology

REDIRECT Species complex#Species flock

group of closely related organisms with low morphological diversity but high genetic diversity

a dubious species name

hypothesis in ecology

Taxonomic term indicating that available data suggests that the proposed species has an affinity to, but is not identical to, the species with the binomial name it comes after

Nature organisation