By decomposing living material.
Answer: 43 x 10^6 CFU.
Explanation:
Plate count is a method used to determine the number of viable microorganisms in a sample. When the bacterial concentration is high, serial dilutions are carried out in a 1:10 sequence. <u>Then, the dilutions are successive dilutions keeping the dilution factor constant at each step</u>. Small aliquots of these dilutions are seeded in medium contained in a Petri dish where the bacteria grow forming colonies. Then the plates are incubated and colonies develop both within the agar and on the surface.
If the concentration of the seeded aliquot is too high, the bacteria will grow too much and it will not be possible to distinguish the colonies. <u>However, if the concentration is very low, the number of colony forming units (CFU) may be very low and thus can be counted</u>.
Colony forming units are calculated:
CFU = Number of colonies / (volume seeded on the plate * dilution).
The dilution is 10^-6, the number of colonies counted is 43, and usually the volume plated is 0.1 mL, so we replace that in the equation:
CFU= 43 / (0.1 mL * 10^-6)
CFU= 43000000 = 43 x 10^6
The correct option is this: TWO DRAGONFLY SPECIES REGULARLY MATE BUT THEIR GAMETES ARE INCOMPATIBLE.
In biology, there are different types of reproductive barriers, one of these is prezygotic barrier. A prezygotic barrier is a kind of mechanism that prevent reproduction from occurring by blocking fertilization. In this case, the concerned species will be mating together, but their gametes will not be compatible and thus, zygote will not be formed.
A postzygotic barrier on the other hand is said to occur when the reproduction process is blocked after the formation of zygote or after fertilization has taken place. A good example of this is an hybrid mule that is sterile and can not reproduce.
