Answer:
The evidence suggests that these chloroplast organelles were also once free-living bacteria.
Explanation:
The endosymbiotic event that generated mitochondria must have happened early in the history of eukaryotes, because all eukaryotes have them.
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The one which is responsible for transmitting an impulse across a synapse to another cell is the neurotransmitters. It allows the transmission of signals from one neuron to the next across synapses.
The correct answer among the choices is letter C.
Answer:
The fossils that provide information on the formation of an oxygen-rich atmosphere are the stromatilites from the Precambrian era. These are layered and columnar fossils consisting mainly of cyanobacteria which were the original life form back then. These bacteria took in carbon dioxide and produced oxygen by photosynthesis as early as 2.5 billion years ago (the earth is about 4.5 billion yrs old).
Explanation:
