Amino acids are required for the synthesis of proteins. Living cells typically have biosynthetic pathways to synthesize at least some of the amino acids used in making proteins. Some strains of E. coli, a prokaryote, can synthesize the amino acid tryptophan, while other E. coli strains cannot. Similarly, some strains of the yeast S. cerevisiae, a eukaryote, can synthesize tryptophan, while other S. cerevisiae strains cannot. Similarly, some strains of the yeast S. cerevisiae, a eukaryote, can synthesize trypotphan, while other strains cannot.
Which of the following describes the most likely source of genetic variation found in the trytophan synthesis pathways of both species?
a. Exchange of genetic information occurs through crossing over
b. Viral transmission of genetic information required to synthesize tryptophan occurs
c. Random assortment of chromosomes leads to genetic variation
d. Errors in DNA replication lead to genetic variation

Answer is option"b"

Explanation:

Sequencing a large number of prokaryotic genomes from an assortment of phyla and classes has offered new chances to contemplate prokaryotic evolution. There are a few techniques to contemplate the atomic  evolution of genomes through quality exchanges. The ordinarily utilized one is through looking for grouping closeness utilizing phylogenetic models, however various different methodologies incorporate recognizable proof of codon use designs, base organization (GC content) investigation, and nucleotide-design properties inside genomes that vary from the genomic standard, as these are probably going to speak to obtained successions.  Pathway evolution has been contemplated from the "starting point of life" setting, and two speculations have been advanced to clarify the advancement of the arrangement of steps in a pathway. Right now, endeavor to contemplate pathway evolution from an alternate point of view. Intracellular biosynthetic pathways comprise different response steps catalyzed by proteins, whose qualities for the most part structure a gathering (operon) in microorganisms.Hence, the right answer is option b" Viral transmission of genetic information required to synthesize tryptophan occurs.

Mantle convection  is the slow  creepingmotion of earth's solid silicate  mantle  caused by  convection  currents carrying  heat from the interior  to the planet's surface.[1][2]  the earth's surface  lithosphere, which rides atop the  asthenosphere  (the two components of the  upper mantle), is divided into a number of  plates  that are continuously being created and consumed at their opposite  plate boundaries. accretion occurs as mantle is added to the growing edges of a plate, associated with  seafloor spreading. this hot added material cools down by  conduction  and  convection  of heat. at the consumption edges of the plate, the material has thermally contracted to become dense, and it sinks under its own weight in the process of  subduction  usually at an  ocean trench.[3]this subducted material sinks through the earth's interior. some subducted material appears to reach the lower mantle,[4]  while in other regions, this material is impeded from sinking further, possibly due to a phase transition from  spinel  to  silicate perovskiteand  magnesiowustite, an  endothermic reaction.[5]the subducted oceanic crust triggers  volcanism, although the basic mechanisms are varied. volcanism may occur due to processes that add buoyancy to partially melted mantle causing an upward flow due to a decrease in density of the partial melt.secondary forms of convection that may result in surface volcanism are postulated to occur as a consequence of intraplate extension[6]  and  mantle plumes.[7]it is because the mantle can convect that the  tectonic plates  are able to move around the earth's surface.[8]mantle convection seems to have been much more active during the  hadean  period, resulting in gravitational sorting of heavier molten  iron, and  nickel  elements and  sulphides  in the core, and lighter  silicate minerals  in the  mantle.

D. china is one of the most active places, which could quite possibly mean more agriculture will happen.. and more war machi-    best of luck comrade.