The most consistent way to obtain information about the evolution of species is to look at the fossil record. Another is to observe the differences between species currently on earth. Another is to use carbon dating.
B. Hydrogen bonds make the positive sides of water molecules stick to each other
The answer to your problem is question 3 i just took that test i got it right
Answer:
Centrioles
Explanation:
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Ventilation maintains a steep concentration gradient, blood at the exchange surface usually has lower O2 and higher CO2 content than the air (of for fish, the water) at the exchange surface. This is what allows for diffusion of O2 into the blood and CO2 out of the blood. Multicellular organisms have a greater number of cells so will have a higher energy demand than single cellular organisms, this demand can only be met by allowing the cells to respire, a ventilation system brings oxygen molecules which are a raw product of respiration into the hemoglobin of the blood to be transported to tissues. As surface area : volume ratio is very low so if there was no ventilation system and the organism instead relied on exchange of materials through the exposed skin it would be very difficult to met the high energy demand as less O2 and CO2 would be able to be exchanged.
