Why were ancient or prehistoric animals got so big?
Have you ever thought why ancient or prehistoric animals were so enormous and huge than today? Ancient animals like Sauropods,the biggest Dinosaur ever discovered were so big? Turtles were in the size of a car,50 foot long snake,Dragon files were in the size of big stone! So why and how this animals got so big? Why modern animals were so little compared to ancient animals? So, lets take a laconic [not absolutely] look at this topic.
Once 300 million years ago, Meganeura, ancient dragon files were in the size of dolphins ! May files were 18 to 20 inches long! Ancient scorpions were 8 inches long! So, finally why they were big? About 300 million years ago, there was a age named Carboniferous period. In that period, the oxygen levels in the air were significantly higher than today,about 30 to 35% of oxygen compared to 21% of oxygen today. Infact more oxygen levels in insects caused disability in regulating their oxygen intake, thus forming oxygen toxicity. So to regulate this oxygen intake, insects grew larger to adapt the oxygen level. In a conceptual term, we can say, bigger the body - larger the oxygen intake, smaller the body -smaller the oxygen intake. Thus, in this way, insects grew huger once millions of years ago.
About 200 million years ago, Reptiles got so huge and enormous. Mostly, Reptiles were cold blooded creatures [Poikilothermic creatures]. About 250 to 66 million years ago, there was a era named mesozoic, the stage was so warm and hot than today's condition. As reptiles were poikilothermic animals, these animals became larger to adapt the warm temperature for their cold body. In tertiary stage, about 66 to 1.8 million years ago, reptiles shrunk to adapt the cold temperature of the tertiary stage. That is the reason, why reptiles became huge. Today's larger reptiles like Komodo dragon lives in hotter dessert to adapt the temperature!
You know Mammals are warm blooded animals [Homeothermic animals]. They generate heat inside the body. In the ice ages, mammals need to become big and huge to adapt the cold climate. In a conceptual way, we can say Colder temperature - bigger the body, Warmer temperature - smaller body. During ice age period, larger mammals evolved. Some of the ice age mammals include woolly mammoths, Sabertooth tigers.
Competition among animals for prey, food, shelter also caused significant role in changes of animals' size. Even competition played a major role in the extinction of animals.
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