42. What is the driving force for water movement within the plants?

6. A copper rod of mass m rests on two horizontal rails with a distance d apart from each other and carries a current i from one rail to the other as shown in Figure 5. The coefficient of static friction between rod and rails is u. A uniform magnetic field B is applied to the system and puts the rod on the verge of sliding, what is the angle of magnetic field with respect to the direction of tails, if the applied magnetic field is at minimum? 

7. Consider a "four-slit" interference experiment as shown in Figure 6. The distance between the slits is d, while the distance between the slits and the screen is D (D＞＞d). A coherent monochromatic light at a wavelength of λ is directed to the slits. Find the distance between the first dark fringe and the central maximum on the screen. 

8. A relativistic particle of mass M with total energy E decays into a lighter particle of mass m together with some other undetected particles. The particle m also decays afterwards. The proper lifetime of particle M is measured to be T and the proper lifetime of particle m is t. If half of the kinetic energy of particle M has been transmitted to particle m during this process, what are the flight distances of the particle M and of the particle m, from an observer at rest? 

二、簡答題41. What chemical bond results in the cohesion between water molecules?

43. What vascular tissues or cells contain this H³/sucrose symporter?

44. Which photosystem is responsible for water splitting?

 (1) What is the "species richness" in these two communities?

(2) Which community has a higher level of diversity?

46. What is the evolved biological function of the CRISPR/Cas system in bacteria? How does the CRISPR/Cas system work in gene editing? 

47. Allopatric populations of two different Darwin's finches show similar beak morphology. However, there are signs of character displacement in sympatric populations of these two species. What does "character displacement" mean? What is the most likely driving force for character displacement?