Million or billion if it's million the answer is false
Natural selection is basically a way for nature to choose what works and what doesn't work. For example, if an animal was born with webs to swim, but most of its food source can be gotten on land, then the animal will die off until it evolves to go on land. That is how evolution works with natural selection. In the past long ago, millions of years back, animals in the water needed oxygen to breath, but the water started to lose it. The land had air, and then the fish slowly grew legs, and their gills would evolve to lungs. Eventually they would be able to roam the land. Because there was so much oxygen with all of the shrubs, trees, and plants, that allowed the bodies of animals to grow big.
The right answer is it can be attributed to similarities among organisms in proteins and nucleic acids (especially in their coding regions in their genome).
Genomes consist of coding regions, which correspond to genes, and non-coding regions. The coding part is the one that gives the proteins that are involved in the structure and metabolism of the individuals. if two individuals have a similar protein-giving genome, then they will probably have the same structure and metabolism.
Pt.I
All living things needs some form of oxygen to live. In talking about a scuba diver, we are talking about a human, who uses their lungs to breathe, and did not develop the ability to breathe under water. Instead, when in a body of water, we tend to hold our breaths until an opportunity arises for us to exchange our carbon dioxide for oxygen.
Take into account the scuba gear. The scuba gear fits the user, and has a number of protection, including the suit counter-balancing any pressure applied by the deep, and the tank providing much needed oxygen to the user during delayed periods within the water.
Pt.II
<u>How does these two systems interact?</u>
Like as a human is breathing on land or even swimming, the human expels carbon dioxide, which forms into "air bubbles" that are then expelled into the water surrounding. The user then draws air from the pressurized air tank, and is able to breathe as such. This allows the user to stay underwater for much longer than just one breathe, and is able to travel farther inside the deep.
Inside this system, the Oxygen is first input into the oxygen tanks, which are then used by the diver. The diver would draw the oxygen from the tank (output), and he will then expel the used air into the surrounding water.
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