Mutations play a critical role in creating genetic variation, which is a fundamental component of biological diversity. A mutation is a change in the DNA sequence that can occur spontaneously during DNA replication or be induced by environmental factors, such as radiation or chemicals. These changes can lead to new traits or variations in existing traits. Some mutations may have little to no effect on an organism, while others can have significant impacts, either beneficial or detrimental. Beneficial mutations can provide an advantage in survival or reproduction and may become more common in the population over generations through natural selection. Without mutations, genetic variation would be significantly reduced, limiting the potential for evolutionary change and adaptation in populations.

Environmental factors significantly influence phenotypic variation, which refers to the observable characteristics of an organism. These factors include aspects like climate, nutrition, lifestyle, and exposure to toxins. For example, the amount and type of food an organism consumes can affect its size, weight, and overall health. Sunlight exposure can influence skin pigmentation in humans and other animals. Similarly, plants growing in different soil types or receiving varying amounts of water and sunlight will show variation in size, leaf colour, and flowering time. These environmental influences often interact with an organism's genetic makeup, meaning that the same genotype can produce different phenotypes under different environmental conditions. This interaction is a crucial aspect of how organisms adapt to their surroundings.

Artificial selection, a process whereby humans select and breed individuals with desired traits, can lead to significant variation within a species. Unlike natural selection, which is driven by survival and reproductive success in a natural environment, artificial selection is guided by human preferences or needs. For example, dog breeding has resulted in a wide variety of breeds with different sizes, shapes, and temperaments, all stemming from the ancestral wolf. Similarly, the cultivation of crops has led to numerous varieties with enhanced qualities like taste, size, or resistance to pests. While natural selection is a random process driven by environmental pressures, artificial selection is intentional and focused, often leading to changes in a species over a much shorter time frame. However, it's important to note that artificial selection can sometimes reduce genetic diversity if it focuses on a narrow range of traits, potentially making a species more susceptible to diseases or environmental changes.

Variation is essential for the survival of a species because it provides the raw material for evolution and adaptation. In a changing environment, having a wide range of traits within a population increases the likelihood that some individuals will possess characteristics that are better suited to the new conditions. These individuals are more likely to survive, reproduce, and pass on their advantageous traits to their offspring. Over time, this process, known as natural selection, can lead to significant changes in the population, potentially giving rise to new species. Without variation, a species may not be able to adapt quickly enough to environmental changes, making it vulnerable to extinction. Variation also contributes to the overall health of a population by reducing the likelihood of genetic diseases and increasing the ability to withstand diseases.

Sexual reproduction contributes significantly to genetic variation through the process of combining genetic material from two different parents. During sexual reproduction, each parent passes half of their chromosomes to their offspring. The key process here is meiosis, where gametes (sperm and egg cells) are produced. In meiosis, chromosomes undergo crossing over, where sections of DNA are exchanged between paired chromosomes. This results in new combinations of genes in the gametes. Furthermore, during fertilisation, when the sperm and egg unite, the combination of these different sets of genes creates a genetically unique individual. This uniqueness is crucial for the genetic diversity of a population, as it ensures that each individual has a different set of traits and characteristics. This genetic diversity is vital for the adaptability and resilience of a species in changing environments.