In biology , especially in theoretical biology and ecology , spread describes all qualitative and quantitative changes in the spatial spread of biological entities. Examples are the spread of species populations P and alleles .

The non-directional form of the spread at the population level, which can be found in many biological systems, is often written somewhat simplistically in the one-dimensional case by biologists:

${\ displaystyle {\ frac {\ partial P} {\ partial t}} = D {\ frac {\ partial ^ {2} P} {\ partial x ^ {2}}} + aP}$.

P is a function of time and space and the expression added to the classic diffusion equation quantifies the local formation of species individuals or the formation of alleles through mutation . ${\ displaystyle aP}$

## Subjects

Biogeography also examines the distribution of species in particular . This is determined by various environmental factors and belongs to the realized ecological niche of the species. This leads to a succession (succession of societies in more or less long periods of time). This is documented by the chorology .

The Geobotany examines the dynamics of vegetation : plants have a variety of dispersal mechanisms developed that will allow them to distribute their seeds sometimes over long distances ( seed dispersal ) secrete or viable plant parts ( Vegetative propagation ).

The zoogeography deals with wildlife . A special form of spreading among animals is animal migration .

The historical development of the expansion is investigated by paleobotany and, in historical periods in connection with human settlement history, paleoethnobotany .

## Resettlement

The penetration of a kind in a non ancestral ecosystem is referred to in the invasion biology as invasive species .

In the sense of a colonization of a new ecotope , the spread of biogenic epidemics is to be understood as it is investigated by epidemiology .