Oxygen did.....filling up space
Answer:
Amino acids may be acidic amino acids, or basic amino acids, due to the R group on the amino acids. If the pH is increased, this affects the shape of proteins, by disrupting the bonds in the protein. In the case of fermentation, you say the rate increases when it get's more acidic - when the pH is lower.
Well, a homologous structure is a bone or something else that is present in many different species that could point to a common ancestor. Since you do not have the examples in your question I will just give you some and hope that it helps you:
The arm of a human, the wing<span> of a bird or a bat, the leg of a dog and the flipper of a dolphin or whale.
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I hope this helped! Let me know if it did not!
I hope you have a fantastical day!!XD