Can a species consist of one population?

They can and exist. But without human protection, such species are doomed. For example, blue fox, Iranian fallow deer or California condor. These are the rarest species subject to international protection.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.