There is quite a lot, but the fact that both mitochondria and chloroplasts have their own circular DNAis what I would call "key" evidence. That is, these organelles are not "manufactured" by the cell (i.e., there are no "genes for mitochondria" in eukaryote genomes): like their ancestral bacteria, they reproduce by binary fission.
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The transfer of antibodies from a mother to the fetus. This occurs naturally, and since it is the transfer of antibodies, it is passive immunity.
We group artworks with similar characteristics into periods or styles because it is easiest to do it that way - this way we can find common characteristics in these literary/artistic eras, and name them. For example, the Renaissance had a distinct style, which differs greatly from that of Romanticism.
Making rough estimate of physical quantities is useful because it allow us to have an idea of how big or small a quantity is, it gives us the near result of the real quantity a matter contains. The approximate quantity obtained will give us information about the size of the quantity.
