They all just formed on top of each other like sedimentary rocks
Natural selection can benefit a species in many ways. One way natural selection benefits a species is by helping a species adapt to constant changing environments and biomes. natural selection can also benefit a species by dying of the weaker links of a species and adapting the mutated species. hope this helped! :)
Answer: 
Explanation:
General representation of an element is given as: 
where,
Z represents Atomic number
A represents Mass number
X represents the symbol of an element
Beta decay : In this process, a neutron gets converted into a proton and an electron releasing a beta-particle. The beta particle released carries a charge of -1 units.

The given reaction would be represented as:

Here are 3 main types of models are ( Physical, Mathematical, and Conceptual. Models have limitations but are useful and can be changed based on a new evidence.