Water was the only type of life on the planet for hundreds of million of years
Stem cells because they are compatible of dividing and renewing themselves after long periods
Answer:
<em>What is the role of alveoli in respiration ⇔ Alveoli are the place where the exchange of gases takes place. The outer part of alveoli has blood vessels. These vessels are carrying Co2 rich blood to exchange at the alveoli. The O2 from the alveoli is diffused into the blood while co2 is sent into the lungs. That O2 rich blood is then carried to heart to pump it to the whole body. and this process continues. </em><em>The alveoli are where the lungs and the blood exchange oxygen and carbon dioxide during the process of breathing in and breathing out.</em>
Explanation:
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Layers of fossils in pillars, the rock covering them is dated and we get an exact time of each layer.
Ribosomes and Endoplasmic Reticulum. Ribosomes are the organelles responsible for protein translation and are composed of ribosomal RNA. So, the answer has to be A and C.