# Artificial selection

**Artificial selection**, also known as **selective breeding**, is a process where **humans intentionally choose** which individual organisms within a population are allowed to reproduce, based on desired traits. This deliberate and planned process aims to "improve" features in organisms.

* **Mechanism and Principles**
  * The process involves **identifying individuals with the most useful or desired features** and using them as parents for the next generation.
  * Progeny showing less desirable features are continuously removed from the breeding population over successive generations. This leads to a **rapid genetic change** in the population, as the frequency of desired alleles increases.
  * Breeders do not necessarily need to understand the underlying genetics; they simply select based on phenotype. This method can be applied to characteristics controlled by many genes.
  * Artificial selection often focuses on improving one or two specific characteristics.
* **Purpose and Goals**
  * The primary goal is to obtain **higher yields, superior nutrient content, or increased resistance to diseases** in crops and livestock.
  * Examples include breeding:
    * **Wheat and rice** for disease resistance and improved yield.
    * **Maize** to produce vigorous, uniform varieties with heavier yields, resistance to fungal attacks, or survival in dry conditions.
    * **Dairy cattle** for improved milk yield.
    * **Horses** for speed or strength.
    * **Cats** for specific traits like pointed ears or fur color/length.
  * It aims to combine desirable features, like a good ear of seed with a short, sturdy stalk in barley.
* **Impact on Genetic Diversity**
  * A significant consequence of artificial selection is a **reduction in genetic diversity** within a population. This occurs because the alleles of unselected organisms are effectively removed from the gene pool.
  * This loss of variability can make the new varieties more **prone to diseases** and less able to adapt to changing environmental conditions.
  * **Inbreeding**, often common in artificial selection programs, can lead to **inbreeding depression**, where the proportion of debilitated offspring increases. This is because inbreeding increases homozygosity, potentially causing harmful recessive alleles to be expressed.
* **Comparison with Natural Selection**
  * **Similarities**: Both artificial and natural selection involve individuals with particular characteristics being more likely to pass on their genes.
  * **Differences**:
    * **Selective Agent**: In artificial selection, **humans are the selective agent**. In contrast, **the total environment** acts as the selective agent in natural selection.
    * **Goals**: Artificial selection aims for phenotypes desired by humans, which may not always be advantageous for the organism's survival in a natural environment. Natural selection, however, leads to adaptations that increase an organism's fitness and survival in its prevailing conditions.
    * **Speed and Magnitude of Change**: Artificial selection can produce **bigger changes in fewer generations** and is generally faster than natural selection.
    * **Genetic Diversity**: Artificial selection **lowers genetic diversity**, while natural selection tends to maintain or even increase it.
    * **Mating Patterns**: Inbreeding is more common in artificial selection, whereas outbreeding is more common in natural selection.
    * Artificial selection typically involves humans having a specific goal in mind, unlike natural selection, which is a non-teleological process.