1. Artificial Selection & Natural Selection

2. What is Artificial Selection? Artificial selection is the process of breeding plants and animals for particular traits. It is also called “selective breeding”. This selection process is "artificial" when human preferences for specific traits have a significant effect on the changes in a particular population or species.

3. Selective breeding tries to establish certain traits that animals will pass to the next generation. These are traits that humans find desirable in domesticated species such as disease resistance, strength, calmness, more lean meat, endurance, etc. Advantages of Selective Breeding

4. Breeding from too small a gene pool can lead to the passing on of undesirable characteristics or even a collapse of a breed population due to inbreeding. Breeding for only one trait, over all others, can cause associated problems. Example 1: Certain roosters bred for fast growth or heavy muscles did not know how to perform the typical rooster courtship dance. The dance bonds the roosters to the hens. No mating dance led the roosters to kill the hens after reproducing with them. Example 2: Many “purebred” dog breeds inherit physical problems that are common to their breed (hip displasia in German Shepherds, respiratory problems in Pugs, etc.) Disadvantages of Selective Breeding

5. What is Natural Selection? Natural selection is the process organisms better adapted to their environment tend to survive and produce more offspring. This is observable.

6. “The Struggle for Existnce” and “Survival of the Fittest” The Struggle for Existence: members of each species have to compete for food, shelter, and other life necessities. Survival of the Fittest: Some individuals with certain traits better suited for the environment and will survive to reproduce the next generation.

7. What is the difference between natural selection & mutations? Mutation= A random change in an organism’s DNA. Can be inherited – passed down from a parent to their offspring Can be caused by carcinogens (cancer causing agents in the environment) EXTREMELY RARE!

8. Mutation = a random change in an organism’s DNA

9. Negative mutations hurt the organism’s chances for survival Mutated blood cell (person with sickle cell anemia) Normal red blood cell Most mutations are NEGATIVE (harmful)

10. Neutral mutations do not affect the organism’s survival (the mutation does not help or hurt the organism) Some mutations are NEUTRAL (not harmful, not helpful) syndactyly bright green feather mutation Normal (dark green feathers)

11. Very few mutations are POSITIVE (helpful) Helpful mutations provide an advantage which helps the organism survive In bacteria, a wide range of mutations can be shown to provide a beneficial phenotype to the cell. These benefits are often of sufficient phenotypic affect that they can undergo strong positive selection. But the benefits are generally temporary and limited. Some common examples of beneficial mutations are those involved in bacterial antibiotic resistance. These mutations potentially enable the bacterium to survive exposure to various antibiotics, but the resistance results from loss or reduction of pre-existing activities such as enzymatic, regulatory, or transport systems.

12. Very few mutations are helpful Most mutations harmful Some mutations can have no effect (NEUTRAL)

13. Darwin’s Theory of Evolution by Natural Selection The Theory of Evolution is the process by which different kinds of living organisms are thought to have developed and changed from earlier forms during the history of the earth. Microevolution (natural selection; changes within species) Macroevolution (one species changes to another species) A theory is an idea or set of ideas that is intended to explain facts or events.

14. Darwin’s Reasoning Observed that a population can outgrow its resources which would lead to competition for existence among offspring. Observed that certain variations are more likely to survive and reproduce (“natural selection”). Assumed that the earth was very old. Assumed that small changes over time can eventually lead to larger changes over a long enough period of time (one species changes into something different = “evolution”). Evolutionary Terminology: Descent with Modification: each living organism has descended, with changes from other species over time. Common Descent: all organisms are come from a single common ancestor

15. Common Descent & Descent with Modification

16. Giraffe Theory = An evolutionary explanation why giraffes have long necks. Giraffes with longer necks had an advantage. They could reach leaves other giraffes could not. Therefore, the long-necked giraffes were more likely to survive and reproduce (greater fitness_. These giraffes passed the long-neck trait to their offspring. Each generation, the population contained more long-necked giraffes. Eventually, all giraffes had long necks.

17. Giraffe Theory – HOWEVER… Female giraffe necks are 2 feet shorter than males. If longer necks were needed to reach above the forage line, then females would have starved to death. NO EVIDENCE in the fossil record of gradual increase the neck. Giraffe “adaptational package”: exceptionally large heart (3 x’s man’s heart); blood pressure control; oversized lungs; respiratory rate 1/3 of humans; capillaries are very internal and 1/3 the size of humans.

18. “Darwin’s Finches” Darwin's finches are 13-14 different species of finches living on the Galapagos Islands (considered an icon of evolution). Each island has its own variety of finch, with the most importance difference being the size and shape of their beaks used for different diets and lifestyles.

19. “Darwin’s Finches” Some had large beaks used for cracking nuts and seeds, while others had slender beaks suited for catching insects etc. The explanation for this given by Darwin was that all the finches on the islands came from one original pair of finches, and that natural selection is responsible for the differences. Because of the variations in the finches he inferred that all species on earth had evolved from this process over billions of years.

20. Current Research Researchers are now discovering that organisms can robustly adapt to different ecological niches without major changes in their DNA sequence. A team of Princeton scientists have won a prestigious award for 20 years of study of the finch's beaks. Just what was found? The two scholars, Drs. Peter and Rosemary Grant observed how, under drought (dry) conditions, birds with larger beaks were better adapted than others, thus their numbers increased. But this trend reversed when the conditions reversed and it became wet again. Furthermore, in times of drought, the normally separate species were observed to cross- breed. They are related after all. But is this really evolution? Even after the changes there is still the same array of beak sizes and shapes. This is variation and adaptation, not evolution. Actually, de-evolution has occurred; the observation is that there are larger groupings of species into what may be more reminiscent of the original kind. INTERPRETATION OF THE DATA IS KEY.