If an index fossil whose absolute age is used as a reference for other fossils, it was determined only by radioactive dating or another absolute method.
Cancers are classified according to the type of tissue in which the cancer arises, <span><span>according to the International Classification of Diseases for Oncology.</span>
</span>
Most autotrophs make their "food" through photosynthesis using the energy of the sun. Heterotrophs cannot make their own food, so they must eat or absorb it. Chemosynthesis is used to produce food using the chemical energy stored in inorganic molecules
The levels of energy are the sun that our main energy source