EvoLution -BIO402 Group 6

1. How might differential expression and regulation by HOx genes contribute to mosaic evolution in which different segments of an animal body plan evolve different morphology?
2. If mutations such as those of the Ubx gene can drastically change morphology in a single step, why should most evolutionary biologists maintain that evolution has generally proceeded by successive small steps?
3. Describe how convergent evolution of similar morphology in two different lineages might involve DNA sequence evolution in different parts of the same developmental gene.
4. Would you predict that novel structures that require complex morphogenetic processes are more often gained or lost in evolution? How might you address this question given a group of organisms with known phylogenetic relationships that vary with respect to the presence or absence of a complex structure such as eyespot or a pair of appendages modified for feeding?
5. How might regulatory DNA sequences underlying a heterochronic change (e.g. an increase in the developmental rate of the larval stage of an insect, resulting in a shorter larval period) differ from those responsible for an evolutionary novelty in a particular body segment (e.g., a novel wing pigmentation spot)? What spatio-temporal components of the development system would you expect to be acting in these two cases, and what sorts of genes (encoding transcription factors, signaling proteins, hormones) would you look for as a candidate genes underlying these two types of evolutionary change?

6. Development of a morphological structure involves many different types of gene products, including transcription factors, signaling proteins, and "effector" genes such as enzymes. When a morphological change occurs in a single mutation step, which of these types might be more or less likely to ve involved? Within a gene, would such single-step events be more likely to involve coding or non-coding sequences, and what characteristics of the gene's function might affect this likelihood?

7. When a lineage loses an ancestral character (such as the loss of wings in the ancestor of the Phasmatodea), how do you think a derived lineage, such as the stick insect, might regain the lost trait? What ecological or population-level factors might act to cause the disappearance of the trait, and what factors might be involved in regaining or maintaining the developmental pathway needed for morphogenesis of that trait?

8. Researchers have used artificial selection (see Chapter 9) to alter many traits in Drosophila melanogaster, such as phototactic behavior and wing length. No one has selected Drosophila (about 2 mm long) to be as large (ca. 30mm) as bumblebees. Can it be done?

9. Suppose you are discussing the evidence for evolution with someone who does not believe in evolution. What evidence would you present to show that different lineages (e.g humans and chimpanzees) have evolved from a common ancestor?