The index fossils are the fossils that come in very handy for the geologists when it comes to identifying or dating rock samples or other fossils. The reason for this is that the index fossils have already been dated. They are fossils that are very commonly found, wide dispersed, are easy to be identified, and are limited to only a certain geological period. These characteristics make them an excellent indicator for the dating of the rock layers in which they are found, or the fossils found in the same layers with them, without conducting further examinations.
According to the question, mating between two populations of Rhagoletis produce hybrid flies.
This means that the two population is present in the same habitat or locality, hence they are capable of coming in contact with each other and mate. Hence, the answer cannot be Habitat Isolation.
Mating produces hybrid flies. This is possible when the gametes (egg and sperm) of the two different populations are capable of capable of coming close to each other and undergoing fusion (fertilization). Hence, there is no Mechanical Isolation.
The zygote formed by the above fertilization is capable of developing into healthy hybrid flies with normal life span. Hence, Pre-zygotic Isolation is absent.
But the hybrid flies formed are sterile and not fertile, that is, they are incapable of producing viable gametes which can undergo fertilization and produce a new offspring.Therefore, the eggs laid by the hybrid flies hatch less often. Hence, there is existence of Reduced hybrid fertility.
You know that there is a difference between plant cells and animals cells. The plant cells have a cytoplasm while the animal cells do not. Therefore the answer must be C.
