One big reason for this is because individuals of the same species often have to fight over shared resources (this means shared food and shared environment).
Because they fight over a limited amount of space and food, competition between individuals within one species can be present and very tough.
On the other hand, having members of different species also possibly means different territories and different food sources. A lion has no quarrel with dolphins, while it can have a lot of fights with lions from different prides (large group of lions).
Earth's crust is generally divided into older, thicker continental crust and younger, denser oceanic crust..The crust is made of solid rocks and minerals.
The mantle lies between Earth's dense, super-heated core and its thin outer layer, the crust. The mantle is about 2,900 kilometers (1,802 miles) thick, and makes up 84% of Earth's total volume.
The core lies beneath the cool, brittle crust and the mostly-solid mantle. ... Earth's core is the very hot, very dense center of our planet. The ball-shaped core lies beneath the cool, brittle crust and the mostly-solid mantle.1
I have a question are you asking what are the molecules of a shark or something
True, muscle tension can make the muscle sore or it can even pull it. Muscle fatigue is the first step for pulling a muscle.