1) Algae belong to the Plant Kingdom, because these are autotrophic photosynthetic organisms with a characteristic cellular structure: the presence of chloroplasts, vacuoles and a cell wall. 2) Algae are lower plants, because they have no organs (no roots, no stems, no leaves), their vegetative body is a thallus, or thallus. They have unicellular gametangia. 3) Algae, like lower plants, do not have tissues (or, there is no differentiation of the body into tissues).
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.