How does Evolution happen? Mutations

• All species exhibit genetic variation. • Mutations affect the individual and can also influence future generations through

inheritance. • Mutations can be Neutral, Harmful, or Beneficial (ie: think of them like typos in

the genetic code… they happen very often). • Neutral – while there is a change in the DNA, it has no immediate effect on the

individual. Most common mutation. • Harmful – can affect the reproductive success of an individual. • Beneficial – can give an organism a better chance at survival in their environment,

and enhances their chances of reproductive success. Least common mutation. • While some mutations are a good thing, for example, the sickle-cell allele gives

carriers a high degree of resistance to malaria and dramatically enhances their chances of survival in regions where malaria is endemic; the changes that arise in a species through mutation can have significant consequences.

• Examples: o Bacteria that have developed resistance to antibiotics are becoming more

widespread as less-resistant strains are killed off. o Insect and other pest species that have developed resistance to various

pesticides are becoming more common and difficult to control. • Some mutations cause significant concerns for our health. Viruses like influenza

can change or mutate over time. Sometimes this can make it easier to spread, which can make it a deadly epidemic. Every year scientists predict which virus strains pose the greatest threat and use it to develop a vaccine.

Human Impact Humans have greatly affected the evolution of many species over time, mainly in the domestication of plants and animals, which provide the majority of our food supply and form the basis for development. Selective Breeding Domestication: Changing of a species to suit our human needs. Artificial Selection: breeding in captivity where humans choose which specific animals and plants are bred. Why do breeders do this? To ensure that a particular trait is passed on to future generations. It can be slow to show significant results. Examples of Selective Breeding:

• Wolves (Canis lupus) to domesticated dogs (Canis lupus familiaris)

• Wild horses to race/jumping horses • Wild sea cabbage/Wild mustard (Brassica

oleracea) to cabbage, cauliflower, broccoli, cabbage, Brussels sprouts, kohirabi, kale

Modern breeding, especially for crop plants, dramatically changed things. Genetic engineering allows scientists to transfer the beneficial genes from an individual of one species to an individual of another species. The genetically modified individual is then cloned for mass production. The Power of Artificial Selection

• Individuals exhibit traits way beyond the natural viability of the original species. • Can reduce genetic diversity within a population - can make the population more

vulnerable to disease. Limitations of Artificial Selection

• Breeders cannot create traits that do not already exist in some form within the population, unless there is a mutation.

• Sometimes a beneficial mutation will be accompanied by an undesired one.