Answer:
The placement of fossils throughout the surface layers of Earth made the geologists decide where one division of the geologic time scale ends and the next begins.
Explanation:
Fossils play a major role in identifying or deciding the geologic time scale eras or eons. Fossils are the only evidence in the form of specimen remains like bones, leaves, shells, teeth, or burrows, tracks etc all of which provide information about life on Earth during a particular time.
Fossil placement on earth’s surface creates fossil records. On the earth’s surface like rocks, a younger fossil will be buried on a layer above the older fossil layer. Each layer will represent a unique life form that existed during a time period and determines the division of geologic time scale.
In fact each of the eras like Paleozoic, Mesozoic, or Cenozoic ends with the suffix zoic since the time change of these eras is based on the evolution of animal life during that period
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Answer:
C. When air temperatures are cool and the ground is wet
Embryologist study embryos because Embryology is central to evolutionary developmental biology ("evo-devo"), which studies the genetic control of the development process (e.g. morphogens), its link to cell signalling, its roles in certain diseases and mutations, and its links to stem cell research.
Answer:
d. a single nucleotide insertion downstream of, and close to, the start of the coding sequence.
Explanation:
A <u>single nucleotide insertion downstream and close to the start of coding sequence will produce the most harmful effect</u> among all these given options because it will cause the <u>entire reading frame to shift in the beginning itself leading to insertion of wrong amino acids in the entire polypeptide chain</u>, hence the entire protein will have extremely different amino acids than the original protein was supposed to have and such <u>protein will be dysfunctional. </u>
In option (a), it is given that the three nucleotides near the middle of the gene will be deleted. This scenario will produce comparatively less harmful effect because in this case only one amino acid which is coded by this deleted triplet codon will be absent in the polypeptide.
In option (b), a single nucleotide deletion has occurred that too in an intron. It will produce <u>no harmful effect in case of eukaryotes</u> because introns are ultimately removed before translation so the amino acids in the polypeptide will remain the same. In case of prokaryotes such deletion may cause some harmful effect in case of mRNA only because introns in prokaryotic mRNA are not removed. But, if the mRNA is for <u>prokaryotic tRNA and rRNA </u>then there will be no harmful effect because they undergo processing in which introns are removed.
In option (c) also there will be very less harmful effect because deletion is occurring near the end of coding sequence which will lead to insertion of wrong amino acid in the polypeptide at the end of polypeptide chain that means very less abnormal amino acids will be present so effect will be less harmful.
