I’m pretty sure the answer is A but if you already ruled that out try B
Answer: (B) Pre-zygotic; post-zygotic.
Explanation:
Prezygotic isolation occurs before fertilization of eggs. It occurs between the two sex gametes and deter sexual reproduction between different species.
However, individuals are considered to be diverge on the phylogeny tree and different species, when they cannot reproduce.
Mechanisms of prezygotic isolation include habitat isolation, gamete isolation, mechanical isolation, behavioral isolation, and mating seasons.
Whereas, postzygotic isolation prevents the formation of fertile offspring. This phenomenon leads to production of an hybrid offspring from different species and this is a form of speciation in nature.
Mechanisms of postzygotic isolation include hybrid inviability, hybrid breakdown, and hybrid sterility.
G1 phase, S phase, and G2 phase
In most mammals, hemoglobin consists of 4 distinct subunits. These subunits consist of an aminoacid chain (aminoacids are the building blocks of proteins) and a heme group. 2 of the subunits have a protein chain with a-structure and 2 have a protein chain with beta structure. The heme groups give hemoglobin and thus blood its red color. Each of these groups has a positively charged iron ion in its core. Iron is necessary so that hemoglobin can bind oxygen and transfer it through the blood flow to the tissues. Given the above exposition, the correct answers are: 4, alpha proteins, heme, iron, oxygen.
Bonus: Hemoglobin is an important example of protein structure since it shows that not only aminoacid order (secondary structure) and configuration of protein chains (tertiary structure) are crucial to the function of a protein; how the multiple chains bind to each other is equally critical (quaternary structure).
The answer is coexistence.
When two organisms are found in the same niche they can not generally coexist in the long term. But it is possible that one of the two organisms adapts to the lifestyle of the second organism, or one of the two organisms disappears (by extinction or by migration).
