A soul is a soul, whether that of a bee or a donkey or a snake or human (for those who believe so, I don't). Most Hindus will define it as a part of the Supreme Soul. What is supposed to happen is that the soul suffers for the evil deeds of the living being and is rewarded for the good deeds. The form that it will assume in the next life also depends on the deeds. (Hindus and Sikhs believe in 8,400,000 life forms - Lakh Chaurasi - 84 hundred thousand, which is close to current scientific guess of about 8.7 million).
Humans are considered to be the best form and those with evil deeds cannot hope to get a human form. Furthermore, it is possible to attain 'moksha', 'nirvana', 'deliverance', 'enlightenment', 'jnana', 'understanding', only in human form. Therefore, people are advised to make the best use of human form and engage in good deeds. Because otherwise they may not get human form again. It is considered a golden chance.
A famous hymn by Kabir Das (an orphan and a saint highly respected in all Indian religions though raised by a Muslim couple) says:
"Tune rāt gawāyi soye ke, diwas gawāyā khāy ke, hirā janam amol thā, kaudi badle jāy."
(You wasted nights in sleeping, and wasted days in eating; your life was as valuable as a diamond and you exchanged it for cowrie shells)