Biology 106 Dr. Dudash

Study Questions Fall 1999

Study Questions Set #3 - Handed out September 20, 1999.

Due: In Lab the following week.

All answers MUST be TYPED unless mathematical computation is needed.

Use no more than 3/4 of a page of single spaced typed text.

Please answer the following questions:

1. Define individual fitness.

The quantity and quality of progeny produced by an individual.

2. What does Mueller's Ratchet help us to understand?

The potential importance of recombination in reducing the number of mutations carried by our gametes from meiosis which could result in a mutation free individual or an individual possessing fewer mutations in their genetic make up. Compare to an organism that can only reproduce asexually and will gradually increase in the number of mutations present without a mechanism to reduce mutational load of an individual.

3. Define natural selection and provide one example.

The nonrandom and differential reproduction of individuals acting to preserve favorable variants and to eliminate less favorable variants in the presence of natural competition OR the differential survival and reproduction of individuals that has a genetic basis. EXAMPLE - many - just make sure that they make sense and demonstrates that the student understands the concept.

4. What was Darwin's evidence for evolution, list 3 components.

1. Artificial selection can canuse large changes across generations.

2. Age of earth - though not uniformly believed by all to be muc older than previously thought..

3. Fossils resemble living animals and fossils in odd areas (ex., sea shells on Mt. tops ~ Macroevolution = changes above the species level.

4. Microevolution - changes among different populations of a species.

5. Define evolution and list two processes that can cause evolution in natural populations.

Evolution is defined as a change in allele frequency at a particular locus within a population over time/ across generations. Processes that can cause evolution are mutation, gene flow, genetic drift, and natural selection.

6 "What Darwin Never Saw" provided us with a unique opportunity to observe Darwin's basic principles in action in the modern day. Please answer the following.

a. How many species of finches were described by Darwin? Do they all exist today?

13, YES

b. Under what conditions and in what direction did they see the medium ground finch evolve in 1977-1978 and in 1983-1984?

1977-78 drought for 18 months, selected for birds with bigger beaks (and body mass) able to crack open very large hard seeded fruit. Starvation occurred in small beaked birds since they had no food source. In next generation the baby birds were found to be 3-4% larger (beak and body) than the grandparents. In 1983 El Nino, it rained for 8 months, population grew from 100 birds to > 1,000 birds. Competition intense by all birds. The medium ground finch that had been selected for because it could crack open those large hard seeded fruits was now suffering because the plant that produced these fruits was shaded from all of the surrounding vegetation which greatly reduced its seed and fruit production ( owing to the extensive rains the plant growth on the island was tremendous). So this group of birds starved during this period owing to competition for the other food resources and there were not enough of the particular plants to feed these birds. The medium ground Finch evolved again and in the opposite direction from 1977-78 towards smaller beak and size (owing to reduced food resources) in the subsequent generation.