Answer:
Species separated by a physical barrier for a long time, suffer allopatric speciation, so they can not interbreed anymore.
Explanation:
Allopatric speciation consists of the geographic separation of a continuous genetic background giving place to two or more new geographically isolated populations. These separations might be due to migration, extinction of geographically intermediate populations, or geological events. In this speciation, some barriers impede genetic interchange, or genetic flow, as the two new populations that are separated can not get together and mate anymore. These barriers might be geographical or ecological.
Vicariance is the geographical separation of an original population into two or more new groups. Discontinuities in the physical environment like rivers, mountains, water, etc., are physical barriers that impede genetic flow between the separated groups.
The process of allopatric speciation involves different steps:
- The emergence of the barrier.
- Interruption in the genetic interchange
- The occurrence of new mutations and their accumulation in time in each population. Slow and gradual differentiation.
- Genetic divergence by natural selection and reproductive isolation makes it impossible for the two groups to mate even if the barrier disappears.
- Prezigotic isolation mechanisms favored by selection once occurs a secondary contact between the new species in formation.
Answer: Polygenic inheritance
Explanation:
Polygenic inheritance is a phenomenon that explains how a character like skin color show a range of more or less continuous variation due to many genes controlling it. And this is unlike Mendel traits that are controlled by single genes.
So, skin color in an individual is expressed as red hair and pale skin.
RNA and DNA-RNA hybrids are more dense than simply DNA if the density of different nucleic acids is tested using a CsCl gradient.
The primary technique employed in molecular biology is the extraction of DNA, RNA, and protein. Scientists can separate materials according to size, shape, and density by using density gradient centrifugation. Isopycnic centrifugation, a sort of density gradient centrifugation that Meselson and Stahl developed, employed a cesium chloride solution to separate DNA molecules solely on the basis of density. Because DNA has hydrogen bonds between its strands, which makes it less dense than RNA, RNA has a far larger density than DNA. RNA can be obtained at the test tube's bottom using a CsCl density gradient and high centrifugation, whereas DNA can be recovered in the middle layer.
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