1) filter feeders of fresh water (for example, toothless, pearl barley) and sea (for example, mussel, oyster, scallop) water bodies;
2) participants in food chains; human food (for example, oyster, mussel, scallop);
3) sources of pearls and mother-of-pearl (for example, pearl barley, pearl mussel);
4) pests of wooden ship bottoms and piles (for example, mussel, ship worm).
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.