Evolution by Natural Selection: Hardy-Weinberg Equilibrium and Beyond

Our best explanation for the diversity seen in the natural world is called the theory of evolution by 'natural selection'.
The principles of the Hardy-Weinberg theory help us understand the driving forces of evolution by providing a baseline for comparison. The theory states that in the absence of certain factors such as mutation, migration, genetic drift, or natural selection, the frequencies of alleles and genotypes in a population will remain constant over generations. Any deviations from this equilibrium can indicate which factors are at play and driving evolution.
The five assumptions of the Hardy-Weinberg equilibrium are:

No mutation: The alleles in the population do not change due to new mutations.
No migration: There is no immigration or emigration affecting the gene pool.
Random mating: Individuals mate randomly and not based on specific traits or preferences.
Large population size: The population is large enough so that genetic drift does not significantly affect allele frequencies.
No natural selection: There is no differential survival or reproductive success based on specific traits.

To estimate the rate of heterozygotic carriers (Ss) of sickle cell anemia, we can use the Hardy-Weinberg equation. Let's assume q represents the frequency of the recessive allele (s) and p represents the frequency of the dominant allele (S). Given that 2% of the population has sickle cell anemia (ss), we can use the equation p^2 + 2pq + q^2 = 1, where p^2 represents the frequency of SS, 2pq represents the frequency of Ss, and q^2 represents the frequency of ss. If we plug in the values, we get 0.02 = q^2. Taking the square root of both sides, we find q = 0.1414. Since q represents the frequency of the recessive allele, the rate of heterozygotic carriers (Ss) would be 2pq, which is 2 * 0.1414 * (1 - 0.1414) = 0.2416, or approximately 24.16%.
Sexual selection can lead to 'handicap traits' through the process of mate choice. In some species, individuals with certain traits that may appear as handicaps or disadvantages, such as elaborate ornamentation or exaggerated physical features, are preferred by the opposite sex during mate selection. This preference for specific traits can lead to the perpetuation and amplification of these traits in the population, even if they may seem detrimental to survival or overall fitness. An example is the peacock's extravagant tail feathers. The male peacock with the largest and most elaborate tail feathers is preferred by the female peacock during mating, despite the fact that the tail feathers can hinder the male's ability to fly or escape predators.
A disease can cause a population to evolve through natural selection. When a disease affects a population, individuals with certain genetic traits may have higher chances of survival or resistance to the disease compared to others. As a result, those individuals are more likely to reproduce and pass on their advantageous traits to the next generation, while individuals without those traits may have lower survival and reproductive success. Over time, this can lead to a change in the genetic composition of the population, as the frequency of the advantageous traits increases.
No, selective breeding of dogs is not the same as natural selection. Selective breeding is a human-driven process where specific traits are intentionally chosen and bred for, often resulting in significant changes in the appearance and behavior of dogs. Natural selection, on the other hand, is a natural process where traits that provide a survival or reproductive advantage are more likely to be passed on to future generations. While selective breeding can lead to variations within a species, it does not involve the same mechanisms and pressures as natural selection.