The core is the innermost layer of the earth. It is a very hot, dense center of the earth that is beneath the solid mantle and crust that are cold. It is a solid ball that has about a 3485-kilometer radius.
The core of the earth is very hot regions which are said to be because of radioactive decay of different elements.
To a certain extent, population numbers are self-regulating because deaths increase when a population exceeds its carrying capacity. Disease, competition, predator-prey interaction, resource use and the number of populations in an ecosystem all affect carrying capacity.