Homework SourseWhat are the arguments that all living cells evolved from a
Solution
Answer:
a. The evidence for a universal common ancestor is very strong. Every examined form of life has a genetic code that is identical or ~99 percent identical to the genetic code of every other examined form.
In modern times the differences can be literally counted in the genome. If you take the sequence for, say, hemoglobin, and compare that sequence in multiple species (human, chimp, dog, bear, cow, whale, etc.), you will generate a tree of more and less similar forms. If you then consider another sequence (say, for insulin) you will get the same tree. The number of possible trees between a bunch of organisms quickly grows to be colossal, but the same tree is drawn and redrawn. If this is not a family tree we are being asked to call this a coincidence.
This analysis furthermore applies to the introns, the parts of a gene sequence that are edited out and do not contribute to protein structure. This eliminates concern about accidental resemblance based on convergent evolution.
Evidences that support that all living cells arose from a common ancestor cell are:
i. Cells of all organisms share common metabolic processes, such as cellular respiration.
ii. All organisms cells contain DNA and undergoes transcription and translation.
iii. DNA is sequenced from one species and is inserted into a different species, and codes for the same amino acids.
b. It seems unlikely that the first cell survived to become the primordial founder cell of today’s living world. As evolution is not a directed process with a purposeful progession, it is more likely that there were a vast number of unsuccessful trial cells that replicated for a while and then became extinct because they could not adapt to changes in the environment or could not survive in competition with other types of cells.
