Short-Answer Please read the question carefully and supply the requested information in the space provided. Please answer 12 of the 14 questions.

1. Explain why pyranosyl RNA (pRNA) is of interest in models of the origin of life.

Pyranosyl RNA shows complementary pairing as does typical RNA but strands are not twisted so this makes replication easier in a world without highly developed enzymes

2. Explain why the rate of transmission of a disease organism is important in understanding the evolution of virulence.

Increased disease transmission has the effect of increasing the frequency of infection within individuals and thereby causing conditions for increased competition among infected individuals. With increased competition there is selection for increased reproduction/virulence. With high infection rates high virulence is less costly because it becomes less important for the success of the pathogen for hosts to live long so as to enable transmission.

3. What is parsimony? Discuss its role in evaluating phylogenies remembering to describe how it is useful but also problems with using it.

The principle of parsimony states that simpler is more likely correct. When attempting to assess which of a series of phylogenies is more likely to be correct parsimony is applied and it is used to select the phylogeny that requires the fewest hypothesized evolutionary changes. Parsimony represent only a best guess and there is no guarantee that it is correct.

4. What is the endosymbyont (or symbiotic) hypothesis and why is it important in the evolution of eukaryots?

The endosymbyont hypothesis argues that organelles such as mitochondria and chloroplasts were originally prokaryote cells that have been incorporated by eukaryots host and which are passed down through generations when the host cell replicates. This cooption of the capabilities of these prokaryote lineages gives eukaryots important capabilities (e.g. aerobic respiration and photosynthesis) that they would otherwise not have.

5. Why has uniparental inheritance of organelles evolved?

Uniparental inheritance of organelles has evolved as a mechanism for reducing reproductive conflict between organelles in the host. With multiple transfer (infection) there is selection for organelles that reproduce at a faster rate because better reproducers are more likely to end up in cells in the next generation. The host loses from this competition so by reducing infection rates it reduces the opportunity for this competition and potential; losses resulting from it.

6. Give three reasons (and explain) why complex life cycles start from a single cell?

Starting from a single cell means:

High relatedness that allows cells to find indirect reproduction a reasonable alternative to direct reproduction. That there can be complex development using a single set of instructions. Starting from different bits of tissues complicates the issue of how to replace missing parts.

There can be sex at a regular time in the life cycle preceding large scale development.

7. Why are plants often monoecious?

Two nonexclusive issues were discussed. First, local biases in sex ratio causes dioecious individuals to have lowered reproduction. Individuals who can be both sexes are always producing some of the rare sex so they suffer less and reduce local biases. Second, males in dioecious species have more limited reproductive options after pollination than monoecious individuals because after pollination the have the opportunity to invest in ovules.

8. Describe two differences between prokaryotes and advanced eukaryot cells and explain how they might be preadaptations for multicellularity.

There might be many answers here. Two I like are:

Distinct chromosomes- can carry more genetic information for complex development also allows for crossing over and genetic diversity

Organelles - Chloroplasts and Mitochondria — allow for efficient fixation of carbon and aerobic metabolism, both of which contribute to rapid growth of complex organisms

9. How does being a heterotroph affect the morphology (form) of individuals differently than being an autotroph?

Heterotrophs cannot produce their own food need to find food sources and they can be obtained in different roles including pursuing prey. Where as autotrophs (especially large multicellular ones) are often sedentary and have well-developed root systems heterotrophs have adaptations for collecting food including a digestive system. Many are very mobile to catch prey and this has led to bilateral symmetry, cephalization including a brain, eyes, and mouth on the head., and limbs. Filter feeders may have a radial symmetry like autotrophs but may have other adaptations for feeding such as pneumatocysts.

10 Draw a cladogram (family tree) showing the evolutionary relationships for all classes of vertebrates.

See notes

11. Name two benefits of diploidy that are main effects and two that are side effects and explain why they are classified that way.

Direct benefits are : Heterozygote advantage, masking of deleterious recessives, and greater genetic variation.

Side effects come from higher genetic diversity in the population: greater evolvability and reduced likelihood of extinction. These are populational effects that are not likely to be the result of selection of individuals.

12. If life were replayed from the Cambrian would it look the same or different? Explain.

Two answers are possible here either the Gould answer or my alternative and each is acceptable if it is supported. The anti-Gould view. Life will replay in a generally similar way although exact patterns are unlikely. There are consistent pressures on organisms to conform to environmental pressures that are unlikely to change. For example, plants will need to have roots and this should impose a sedentary life style and radial symmetry. Heterotrophs will have to move after prey and have a digestive system, cephalization and bilateral symmetry.

13. Draw a typical pattern of alternation of generations in plants (e.g. a bryophyte). Please include reproductive structures/propagules, the terms used to characterize the respective stages, when meiosis occurs, and levels of ploidy.

See notes

 

14. Explain why there may be a conflict between chromosomes and the parent individual during meiosis, and describe how this conflict is related to the concept of ‘selfish genes’.

During meiosis when eggs are produced it is common for only one of the four chromatids to go into the ova and the others are shunted into the polar bodies. There is a potential conflict between the individual chromatid and the interests of the rest of the cell. By going into the polar body the chromatid is sacrificing itself and as a selfish gene it should resist this sacrifice.

True/False Questions : Please answer all questions with a clear True of False

1. _T____Variation in the genetic material used by different viruses suggests that there is no single key molecule of life, but that the ability to transfer genetic code is the overriding factor.

2. __T___Iridium associated with the K-T extinction event could have come from either meteor impact or volcanoes thus making it difficult to determine whether the Alvarez or intrinsic gradualist hypothesis is a better explanation.

3. ___F__Angiosperms and gymnosperms are similar in having seeds and flowers.

4. __T___Protostomes differ from deuterostomes by having radial cleavage, a blastopore that becomes a mouth and the loss of cell capability for developing into the full range of cell types.

5. __F___Crustacea and Echinoderms are deuterostomes while Annelids and Mollusks are protostomes.

6. __F___Bryophytes that were dominant during the carboniferous are the main constituents of coal.

7. __T____All chordates have notochords, dorsal nerve cords and pharyngeal gill slits at some time in their life.

8. __F___Three unique characteristics of mammals are a complex jaw articulation (allowing sideways chewing), warm bloodedness, and the live bearing of young.

9. __F____Preadaptations evolve because they permit important future evolutionary changes.

10. __F___The algae Clamydomonomas reinhardi uses restriction enzymes to destroy organellar and nuclear DNA as zygotes form allowing them to maintain constant level of ploidy.

11. __F___The nuclear winter hypothesis explains the evolution of heterotrophs because they can survive without sunlight.

12. ___T__Radial symmetry common in sponges and echinoderms is more likely associated with a sedentary or slow moving lifestyle.

13. __T___Homoplasey refers to characters that are similar because of convergence and these characters are not helpful in developing a cladograms.

14. ___F___The Miller-Urey experiment created nucleic and amino acids and thus was able to resolve the paradox of chemical evolution.

15. __F___Coelomates include annelid worms such as earthworms and pseudocoelmates include flatworms. The mesoderm that splits to form the annelid body cavity arises from cells near the blastopore.