These are examples of homologous structures. Homologous structures are similar because they are inherited from a common ancestor, they are examples of organs or structures that appears in different animals, underlining anatomical commonalities which is evident that they have a common ancestor. Analogous structures on the other hand are structures that are similar in unrelated organs.
Well the <span>blood returns from the cardiac tissues to the right atrium because
the blood goes through the tricuspid</span> valve and into the right ventricle then the right ventricle makes the blood go to the lungs and thats where the oxygen is at then the blood goes through organs and tissues then gets to the heart through the veins and a vein named the vena cave has the blood return to the right atrium.
Cyanobacteria had a role in the evolution of eukaryotic cell, more precisely their organelles. It has been shown that chloroplast, cell organelles found in some eukaryotic lineages, which are specialized in performing the photosynthesis evolved from cyanobacteria through the process called endosymbiosis. In this process, photosynthesizing cyanobacteria was engulfed in some ancient eukaryotic cell. Eukaryotic cells have evolved from the endosymbiotic events.
<span>By producing and releasing O2 (as a byproduct of photosynthesis), cyanobacteria are thought to have converted the early oxygen-poor, reducing atmosphere into an oxidizing one. This caused the Great Oxygenation Event which dramatically changed the Earth's life forms and led to the formation of multicellular organisms.</span>
