Plant Physiology: 1. Plant Hormone signal transduction is an exciting field and the mode of signaling for various hormones in the cellular context have been elucidated. Compare and contrast the plant hormone Auxin and ethylene signal transductions mechanisms. (Hint. Begin at the Receptor level) 2. To cope with drought conditions, plants employ a very common mechanism of synthesizing solutes for osmotic adjustment. Describe how solutes help plant cells to cope with drought conditions. 3. Carotenoids comprise a family of orange and yellow pigments present in most photosynthetic organisms. Describe the different types of carotenoids found in photosynthetic organisms pointing to their chemical characteristics and functions. 4. ATP synthesis in chloroplast is based on the stepwise conservation of energy. Trace the conservation of energy from the initial absorption of light by the chlorophyll molecule to the final formation of a molecule of ATP. 5. Trace the path of carbon in a typical C4 type of plants- from its entry through stomata to its export in the vascular tissue. How does this differ from C3 pathway? Ecology: 1. Answer the following questions to describe interaction between the biosphere and the atmosphere: Discuss the origin of oxygen in the atmosphere. Discuss why oxygen is essential for energy production in most forms of life on earth. Discuss the origin of ozone in the atmosphere and the impact of ozone (in stratosphere and troposphere) in maintaining healthy life on earth. Why is nitrogenase enzyme essential to maintaining the biosphere? 2. Answer the following questions to explain the greenhouse effect in detail: Why was the greenhouse effect important for the evolution of life on earth prior to humans? What are the two most important greenhouse gases? Define and explain the concept of albedo. Define aerosols and explain how aerosols affect warming due to changes in albedo. Explain the positive feedback relationship between warming and albedo in polar regions. 3. Answer the following questions to explain how life histories have evolved as suites of traits that increase evolutionary fitness in different environmental conditions: (1) Name the three principal directions for allocation of limited resources in the life history of any organism. Answer the following questions to compare the life history of an oak tree with the life history of crabgrass (an annual weed). (2) How does seed size and seed dispersal ability differ in these two species, and how do these differences reflect different evolutionary pressures? (3) How