Tutor profile: Simon T.

¿Cuándo usas el pretérito y cuándo usas el imperfecto? (When do you use preterite past tense and when do you use the imperfect past tense?)

El imperfecto es usado usualmente para: -acciones que occure por un periodo largo de tiempo (de años or más) -acciones que occure habitualmente -referencias a la edad en el pasado -referencias a las características en el pasado -referencias a los estados físicos y mentales en el pasado -tiempos y datos Por el otro lado, el pretérito es usado para acciones completadas, que tiene un comienzo específico y un final específico. The imperfect is usually used for: -actions that occur over a large period of time (years or more) -actions that occur habitually -past references to age -past references to characteristics -past references to physical and mental states -time and dates On the other hand, the preterite past tense is used for completed actions that have a specfic start and a specific end.

A flame-test experiment involves taking various metal ions in aqueous form and igniting them with a flame to produce a certain colored-flame. For example, dipping a nichrome wire loop in aqueous strontium and then lighting the wiring in a flame, produces a deep red color in the flame. What causes the color change and light emission?

Light is produced from a photon, which is an emission of light when electrons move from a higher energy level back down to their stable ground state. In the flame test, the electrons are continuously moving from higher to lower levels as that nichrome loop remains in the flame. The color of each element corresponds to their own line spectrum. The photons released corresponds to a particular wavelength in the visible light spectrum. As electrons move from level to level, a spectrum of lines will be produced, some of which will be in the visible part of the spectrum. The colour you see will be a combination of all these individual colours.

If you type in "Gummy Bear Genetics" in Reddit, you'll find a photo of a pedigree, jokingly and inaccurately, attempting to portray gene inheritance. Assume the photo is trying to portray Mendelian genetics. Aside from the obvious display of in-breeding, what are some mistakes about the photo if such an assumption were to be made? Is this applicable to other human traits such as skin color?

We have no indication if gummy bear color is determined by only two alleles. There's a red bear and a yellow bear mating; these parents yield one offspring that is completely orange bear and one that is half red half-yellow. This would not happen in Mendelian genetics because Mendel himself did not conduct experiments on incomplete dominance (orange bear) and co-dominance (half red half yellow bear) You cannot apply this photo to many other traits such as skin color. Skin color, for instance, is exhibited by many genes to create one specific tone. Skin color is thus determined by many different alleles and genes, far too complex to be portrayed by the Mendelian model.