The element found in period 4, group 2 is zirconium, Zr
Answer:
Scientists believe that the different types we know emerged as early humans adapted to infectious diseases.
Explanation:
Different human blood types probably emerged to ward off infectious diseases. The incompatibility of some blood types, however, is only an "accident" of evolution. But this is a relatively recent problem, since blood transfusion has been around for only a few hundred years.
There are four main blood types. The oldest is B, which must have originated about 3.5 million years ago - it existed even before the human species evolved from its hominid ancestors, from a genetic mutation that modified one of the sugars in the surface of red blood cells.
Approximately 2.5 million years ago, mutations inactivated sugar, resulting in type O blood, which has neither type A nor B. sugar. AB blood, as it is easy to suppose, is covered by both sugar A and sugar by B.
Answer:
Homologous
Explanation:
If two or more species share a unique physical feature, such as a complex bone structure or a body plan, they may all have inherited this feature from a common ancestor. Physical features shared due to evolutionary history (a common ancestor) are said to be homologous.
The probable reason for the case would be that the sea floor 200 million years ago is now above the sea level.
The ocean floor is the eventual recycling center. While the Earth's continental crust can prevail for billions of years, the movement of tectonic plates results in subduction, that is when the crust of the ocean is pushed down into the present mantle. So, the ocean floor hardly endures longer than 200 million years.
