Evolution

1. Evolution Natural Selection & Artificial Selection

2. Goals/Success Criteria • Analyze the economic and environmental advantages and disadvantages of artificial selection • Investigate and analyze the processes of natural selection and artificial selection

3. Natural & Artificial Selection • Natural selection: the process that results when the characteristics of a population of organisms change over many generations. • This change happens because individuals with certain inherited traits survive specific local environmental conditions, and through reproduction, pass on their alleles to their offspring.

4. Selective Pressure • Organisms have many phenotypes (observable characteristics) (e.g., hair colour, eye colour) • Many phenotypes are neutral when it comes to survival and reproduction – however, some phenotypes are selected for or against by the environment • E.g., people that live in places with strong sunlight, are likelier to survive if they have dark skin to protect them from UV damage

5. Selective Pressure • Selective pressure: environmental conditions that select for certain characteristics of individuals and select against other characteristics Selective pressure drives natural selection – some members of the population will not survive and reproduce, thus will not pass their genes on to the next generation

6. Examples of Selective Pressure • Climate • Food and energy sources • Predation • Diseases • The immune system • Human manipulation (artificial selection)

7. Fitness • Fitness: the relative contribution an individual makes to the next generation by producing offspring that will survive long enough to reproduce • A high degree of fitness means that an organism will survive and reproduce • An organism with many viable offspring has high fitness, whereas an organism that has few/no viable offspring has low fitness

8. Artificial Selection • People have been artificially selecting organisms for particular traits for thousands of years • Selective breeding is a form of artificial selection (selective pressure exerted by humans on populations in order to improve or modify particular desirable traits) • Selective breeding and artificial selection are a type of biotechnology (the use of technology and organisms to produce useful products)

9. Artificial Selection • Most food we eat (grains, fruits, vegetables, meat, and milk) comes from species that have been selectively bred • E.g., cows that produce more milk, chickens that grow rapidly and have large muscles, chickens that produce a large number of eggs, pets bred for their appearance • Difference: In natural selection, the environment plays the role that humans play in artificial selection

10. Artificial Selection and Food Crops • Food that comprises most of our diet (rice, corn, wheat, and vegetables) are the result of selective breeding • E.g., the wild mustard plant has been modified by selective breeding to create many common food crops – including broccoli, Brussel sprouts, and cauliflower

11. Artificial Selection and Food Crops • Plant breeders began modifying the traits over 4,000 years ago in Europe and Asia • Food crops are bred to increase nutritional value and resists drought and pests

12. Consequences of Artificial Selection • English bulldogs are bred for traits such as flat faces – which results in severe respiratory problems • Genetic engineering is a form of artificial selection which have introduced new genetic information to produce organisms that are all similar – thus, plants that are selectively bred as per grower’s requests lack diversity (monoculture)

13. Monoculture • Monoculture: extensive plantings of the same varieties of a species over large expanses of land • Fields are easier to manage when there is only one kind of plant growing • However, if a new disease infests the crop population, most of the individual plants will be affected in the same way and the whole population could be killed or severely damaged

14. Gene Banks • To protect against disasters – gene banks have been established • Gene banks contain populations of early ancestors of modern plants • By preserving these organisms, their genetic diversity is available for introduction into modern plants – if need arises

15. In the lab… • Half the class will research the advantages of Artificial Selection and half the class will research the disadvantages • Students on each “team” will work together to formulate their argument • Each team will have a chance to present their argument and as a class we will make a table on the board to be copied into your notes