Oxygen concentration in our atmosphere is vital to life. Without oxygen, life on earth would cease to exist. Currently, the oxygen concentration in our atmosphere is around 21%, which means that 21% of the molecules that make up our atmosphere are oxygen molecules, and 79% of the molecules in our atmosphere are from other elements (78% nitrogen and <1% other).
Since a lack of oxygen kills life, would an increase in oxygen make life thrive? What would happen to life on earth, if the oxygen concentration in the atmosphere was 50% higher than today? This would mean that oxygen in the atmosphere would make up ±31% of the atmosphere. A research team at Arizona State University1 did a study of insects in an atmosphere at 31% oxygen concentration (a hyperoxia environment), which is a 50% increase in our current oxygen concentration in the atmosphere. The researchers also studied insects in an atmosphere at 12% oxygen concentration (a hypoxia environment).
The results were staggering; most of the insects raised in hyperoxia conditions were larger in size than normal, which clearly demonstrates a thriving life. Only the cockroach remained the same size. However, the cockroach’s internal tracheae (tubes that carry oxygen throughout the body) were smaller than normal as a result of living in a 31% oxygen environment, which allowed other organs and tissues to grow larger. Other tissues that grew larger were muscles, blood vessels, tendons, ligaments, nerves, and more, which means those cockroaches would be faster, stronger, and quicker and have improved endurance and a faster response time. Therefore, all insects in an oxygen-enriched environment would thrive.
In a hyperoxia (31% O2) environment, insects grow larger. And the ones that don’t seem to grow larger (because of an exoskeleton restricts growth) would eventually grow larger in time as they adapted to the increased oxygen concentrations because of the ability to adapt already exists in the DNA. This is called adaptation or “speciealization” (this is not evolution because they are still the same kind of creature). Photo credit: www.asunow.asu.edu/big-insects-provide-big-answers-about-oxygen.
Conversely, the research showed that the insects grown in hypoxia (low oxygen concentration, around 12% oxygen concentration, which is half of today’s value) were
For this study, the limiting factor of insect growth was oxygen, and varying the amount of oxygen results in changes in the size of tracheal tubes.
1. The higher the oxygen concentration in the air, the smaller the tracheal tubes are required to transfer low volumes of air into the body to get the necessary volume of oxygen into the body as needed.
2. The lower the oxygen concentration in the air, the larger the tracheal tubes are required to transfer high volumes of air into the body to get the necessary volume of oxygen into the body as needed.
Review: Experiments show that higher oxygen concentration in the atmosphere equals thriving life. Life will grow larger, faster, and with greater longevity in an environment with higher oxygen concentrations.
Today, we have cockroaches that are about 2.75 inches long, but the fossil record shows cockroaches that grew to 18 inches long. That is 6.5 times larger. Today, we have dragonflies with a wing span of 6 inches, but the fossil record shows dragonflies with wingspans up to 50 inches. That is 8.3 times larger. Today, the chambered nautilus (it looks like a squid in a shell) grows to about 10 inches in diameter, but the fossil record shows that they once grew to 8 feet in diameter. That is 9.6 times larger.
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