Chromosomes are thread-like structures in which DNA is tightly packaged within the nucleus.
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).
A molecule is a carbohydrate if it contains carbon and water
All isotopes of hydrogen will always contain one proton, as a change in the amount of protons will change the substance. Assuming all isotopes aren’t ions and therefore don’t have a charge, then each of these isotopes has one electron. The only difference between them is the amount of neutrons to account for the different atomic masses.
H1
one proton
one electron
zero neutrons
H2
one proton
one electron
one neutron
H3
one proton
one electron
two neutron