Evolution, Natural Selection, and Artificial Selection Notes

Evolution is defined as genetic, heritable changes in a population over generations.
It represents the unifying theory of biology, explaining the history and diversity of life on Earth.
Populations undergo gradual change over generations in response to biotic and abiotic environmental factors.

Natural selection is a primary mechanism of evolution where differential survival and reproduction of individuals with specific heritable traits lead to changes in a population's genetic makeup over generations.
Four conditions are required for evolution by natural selection to occur:
- The trait must be heritable.
- Genetic variation in the trait must exist within the population.
- Differential survival and reproduction must occur based on environmental factors.
- More offspring must be born than can survive.
Selection pressures such as limited resources, predation, competition, disease, and environmental extremes (e.g., drought or high temperatures) determine which individuals survive and reproduce.
Individuals possessing advantageous traits leave more offspring, making those traits more common in subsequent generations.

Discovered by Alexander Fleming in 1928, the antibiotic penicillin kills bacteria by inhibiting an enzyme crucial for bacterial cell wall biosynthesis.
Antibiotics became widely available in the 1950s as effective treatments for previously fatal infections.
Antibiotic resistance develops because a small number of bacterial cells possess random DNA mutations that alter their biochemistry:
- Exposure to antibiotics kills susceptible cells while resistant cells survive and reproduce.
- Over generations, the proportion of resistant bacteria in the population increases.
The rise in resistance is driven by the overuse and misuse of antibiotics in humans and their inclusion in animal feed.
In response to growing health threats monitored by Health Canada, the Government of Canada released Antimicrobial Resistance and Use in Canada: A Federal Framework for Action in October 2014.

Artificial selection is the process of causing evolutionary change through human choice by selectively breeding plants or animals with desired traits.
Selective breeding increases the frequency of targeted traits in successive generations.
Modern corn (maize) was developed through thousands of years of artificial selection by farmers in present-day Mexico, who selectively planted kernels from teosinte, a wild grass species.