In this article we will discuss about the definition and types of genetic extinction of species.
Definition of Genetic Extinction:
When a species of plant or animal is no longer able to successfully reproduce due to loss of habitat, or numbers they become extinct. It is the evolutionary termination of a species caused by the failure to reproduce and the death of all remaining members of the species; the natural failure to adapt to environmental change.
It is the irreversible process or condition which leads to death of all representatives of a species. Genetic extinction has been defined in various ways.
Some definitions of extinction are given below:
i. The complete disappearance of a species from the earth forever is known as extinction. Thus it is complete global loss of a species.
ii. The elimination of a species due to natural processes or human activity is termed extinction.
iii. Extinction refers to permanent loss of a crop species due to various reasons.
iv. The process by which an animal or plant that once existed can no longer survive and then cannot be found alive anywhere on earth is referred to as extinction.
Types of Genetic Extinction:
All species die and disappear someday. This is known as extinction. In most cases, extinction is a means by which a new species arises.
There are two main types of extinction, viz.:
1. Natural extinction, and
2. Accidental extinction.
These are briefly discussed below:
1. Natural Extinction:
Natural extinction refers to the extinction that occurs naturally in the evolution process. This is also known as background extinction. About 0.00003% of species become extinct naturally according to fossil records. This extinction has been occurring since the origin of life on earth.
During the ecological process, the natural extinction occurs following the evolution of the species. If a species cannot succeed in adapting to its surroundings it eventually becomes extinct.
Factors of background extinction include gradual changes in:
(i) Temperature,
(ii) Humidity,
(iii) Predator-prey relationships, and
(iv) Tectonic plate movements.
It has been estimated that the average species stays around for 4-22 million years before it becomes extinct and that 99.9 % of all the species that have ever existed are now extinct.
2. Accidental Extinction:
When large numbers of species become extinct each year, it is known as accidental extinction or mass extinction. Terrestrial biodiversity has experienced five great mass extinctions during the past 500 million years. These mass extinctions have been 20-60 million years apart and there have also been shorter mass extinctions (loss of 15-24% of all species) in between. A period of mass extinction is often regarded as having a loss of 25-70% of all species. The extinction of the dinosaurs is a fine example of mass extinction.
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