2) Most of our organs are directly innervated by the sympathetic nervo.docx
- 1. 2) Most of our organs are directly innervated by the sympathetic nervous system that can affect their functioning through neurotransmitters. A particularly striking example we discussed is the direct involvement of the brain in the regulation of stem cell differentiation in your hair follicles. Speeded up differentiation of these stem cells by the brain leads to the loss of pigmentation and you turn gray as a result of stressful experiences. Give one adaptive (having current function) and one neutral (having no current function) explanation for this phenomenon. Note that you are asked why it works, not how. 3) In physical sciences, a set of all possible states around an entity that can be reached in the next time step (called "adjacent possible") is usually a point (think of predicting the location of a falling rock of known mass at each time step). In biology, the "adjacent possible" is typically a very large space. Give and explain two reasons for this. Write in complete sentences. 4) Life has two seemingly opposite defining properties: 1) faithful self-replication (e.g. "dogs produce dogs") and 2) continuous evolutionary change. Propose two hypotheses for reconciling these properties (constancy vs. change). Propose a test for each of these hypotheses. 4 sentinces each 5) (a) Give four hypothetical explanations for the hourglass shape of development where early and late stages diverge across species more than a phylotypic stage in the middle. (b) Explain why evolutionary transitions (from adaptation to adaptation) also appear to follow the hourglass shape, i.e., go through a shared bottleneck. 2 setence each