Phenomena is a fact or situation that is observed to exist or happen, especially one whose cause or explanation is in question. Physical phenomena is a natural phenomenon involving the physics of matter and energy.
Patent law classifies physical phenomena as products of nature and if your invention occurs in nature, it cannot be patented. If your invention is a product of nature, it falls under excluded subject matter but if your invention does not occur naturally and can only exist through human work, you might be able to patent it. Identifying a product of nature (discovery) will not be enough to get you a patent, but if you are able to modify that product, it might be patentable.
Genes, hormones, and chemicals that are products of nature, but can’t exist naturally in it’s isolated form and need to be isolated, purified, or somehow altered, might be patentable. You cannot patent a species of animal or a combination of bacteria that occurs by itself in nature. You can patent a genetically engineered mouse or a species of bacteria that you genetically altered.