>The reason why Arthropleura and other Arthropoda could get to such huge sizes compared with the small sizes for this category of animals nowadays, is that oxygen levels were higher in the Permian. Insects breathe by diffusion through a tracheal system, they don't have lungs, so their size is limited by this. There are other theories regarding why insects became smaller, including the appearance of birds as predators of insects, particularly flying insects.
>Regarding the size of dinosaurs, it is speculated that herbivorous dinosaurs got larger because the increased CO2 in the atmosphere allowed for a superabundance of plants that were increasingly larger as well. The carnivores had to follow suit in order to prey on the herbivorous behemoths. The biggest land animal of all times was Dreadnoughtus, which weighed in at about 65 tons, as big as a 747. The biggest land animal today, the African elephant, is 5 tons.
>Interestingly, the biggest animal of all times is the existing blue whale, which weighs about 100 tons. The oceans and other large bodies of water can support the existence of very large animals, because water buoyancy counteracts the gravitational pull. The blue whale can get as huge, because it eats krill, which is one of the most abundant foods on the planet. There is no fossil marine animal that got as big as the blue whale, so perhaps the exceptional gigantism phenomenon observed during the time of the dinosaurs only applied to land animals.
During the Carboniferous and Permian periods, atmospheric oxygen concentrations were significantly higher than they are today. Prehistoric insects breathed air that was 31-35% oxygen, as compared to just 21% oxygen in the air you're breathing as you read this.
Atmospheric oxygen is the single most limiting factor on insect size.
The cells in your body get the oxygen they need to survive via your circulatory system. Oxygen is carried by the blood, through your arteries and capillaries, to each and every cell in your body. In insects, respiration occurs by simple diffusion through the cell walls.
Insects take in atmospheric oxygen through spiracles, openings in the cuticle through which gases enter and exit the body. Oxygen molecules travel via the tracheal system. Each tracheal tube ends with a tracheole, where the oxygen dissolves into the tracheole fluid. The O2 then diffuses into the cells.
When oxygen levels were higher, as in the prehistoric era of giant insects, this diffusion-limited respiratory system could supply sufficient oxygen to meet the metabolic needs of a larger insect.
Oxygen could reach cells deep within the insect's body, even when that insect measured several feet long. As atmospheric oxygen decreased over evolutionary time, these innermost cells could not be adequately supplied with oxygen. Smaller insects were better equipped to function in a hypoxic environment.
And so, insects evolved into smaller versions of their prehistoric ancestors.
>>53559807 it depends actually free radical oxygen is very very bad it destroys cell-lining so we will live shorter lives
there is no immediate height growth but our hearts will pump slower since our bodies would get enough per pump thus the extra energy is stored, only over a long time maybe the body increase in usage but divided in relation to parts of the body that uses energy the most like brain and hands so "we" may not get like 30 meters tall.
dinosaurs did because they were in a pretty "simple" hunter/hunted dynamic
>>53558330 food Earth had much bigger trees back then and plant life. Big herbivores mean big carnivores. I recommend reading on multiple massive extinctions of life on Earth, and how it made good fuel for new life to develop. >can;t wait to become fuel for some awesome plant
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