Which of these three molecules—dna, rna, or proteins—most likely operated in the ancient past prior to the appearance of the other two molecules? explain how this earliest "proto-life" chemical serves more than one function.

RNA

Explanation:

It's important to first acknowledge that in order to sustain life, there needs to exist molecules that can self-propagate. These molecules need to perform essential functions that include:

1) Storing genetic material that can be copied.

2) Be catalysts for processes such as replication and other functions.

Between the 3 molecules, RNA is the only one that has both properties. It is a polynucleotide, meaning that it stores genetic material that can be copied. It can also fold into complex tertiary structures that act as catalysts. Therefore, it is possible that it acted primitively as an autocatalyst making copies of itself, directly or indirectly.

segmentation=endoskeleton=backbone=coelom=tissues

tsd is temerature dependent sex determination.

tsd: it is a type of environmental sex determination in which the temperature experienced during embryonic/ larval development (ambient temperature for development) determine the sex of the offspring.

crocodile displays the tsd where the ambient temperature of the developing egg determines the individual's sex. for example in the american alligator's eggs, incubation at 33 ºc produces mostly males, while incubation at 30 ºc produces mostly females. so if the american alligator's egg will get the ambient temperature (33 degree celcius)during embryonic development from egg, the offspring will be male and same for the female sex determination.