The bottom line: Yes. Without a will, Tennessee law decides who gets your dog, your car, and everything else you leave behind.
If you die without a will, the state of Tennessee, using the law of intestacy, will determine who inherits your property. If you have no spouse or children, your property will be divided equally between your parents. If your parents die before you, then your property passes to your brothers and sisters.
The law of intestacy will not benefit your fiancée, friend, long-time partner, church, or anyone that is not legally related to you. If you want your property to pass to someone other than what the law provides, then you need a will.
A will is just one part of a good estate plan; your estate planning should include documents that determine who will take care of your financial affairs (such as bill paying) if you are incapacitated and who will make medical decisions for you if you are unable to do so yourself.
There are also ways other than a will that your property can pass after your death. For example, insurance policies and retirement accounts have beneficiaries that you name on the policy or account. A trust is a good option in some circumstances. When you review your assets with your estate planning attorney, she can advise you as to the best way to benefit the people or organizations you care about.