Isolating Mechanisms are features of behavior

Behavior

Behavior or behaviour refers to the actions and mannerisms made by organisms, systems, or artificial entities in conjunction with its environment, which includes the other systems or organisms around as well as the physical environment...

, morphology

Morphology (biology)

In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....

, or genetics

Genetics

Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....

 which serve to prevent breeding between species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

. Reproductive isolation

Reproductive isolation

The mechanisms of reproductive isolation or hybridization barriers are a collection of mechanisms, behaviors and physiological processes that prevent the members of two different species that cross or mate from producing offspring, or which ensure that any offspring that may be produced is not...

 of populations is established. It is particularly important to the biological species concept, as species are defined by reproductive isolation.


Isolating mechanisms can be divided into two groups, Prezygotic isolating mechanisms and Postzygotic isolating mechanisms

Prezygotic mechanisms

Factors which prevent individuals from mating.

• Geographic isolation: Species occur in different areas, and are often separated by barriers.
• Temporal isolation: Individuals do not mate because they are active at different times. This may be different times of the day or different seasons. The species mating periods may not match up. Individuals do not encounter one another during either their mating periods, or at all.
• Ecological isolation: Individuals only mate in their preferred habitat
  Habitat
  * Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
  
  . They do not encounter individuals of other species with different ecological preferences.
• Behavioral isolation: Individuals of different species may meet, but one does not recognize any sexual cues that may be given. An individual chooses a member of its own species in most cases.
• Mechanical isolation: Copulation may be attempted but transfer of sperm does not take place. The individuals may be incompatible due to size or morphology.
• Gametic incompatibility: Sperm transfer takes place, but the egg is not fertilized.

Postzygotic isolating mechanisms

Genomic incompatibility, hybrid inviability or sterility.

• Zygotic mortality: The egg is fertilized, but the zygote
  Zygote
  A zygote , or zygocyte, is the initial cell formed when two gamete cells are joined by means of sexual reproduction. In multicellular organisms, it is the earliest developmental stage of the embryo...
  
   does not develop.
• Hybrid inviability: Hybrid embryo forms, but is not viable.
• Hybrid sterility: Hybrid is viable, but the resulting adult is sterile.
• Hybrid breakdown: First generation (F1
  F1 hybrid
  F1 hybrid is a term used in genetics and selective breeding. F1 stands for Filial 1, the first filial generation seeds/plants or animal offspring resulting from a cross mating of distinctly different parental types....
  
  ) hybrids are viable and fertile, but further hybrid generations (F2 and backcrosses) are inviable or sterile.

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