aquatic animals

3. Tiny hair-like structures used for locomotion in flatworms.
4. Having separate sexes in a population.
7. Protective structure produced by some annelids and leeches for egg deposition.
11. A form of asexual reproduction where eggs develop without fertilization.
12. where one organism (parasite) benefits at the expense of another (host).
15. Phylum of segmented worms, including oligochaetes, polychaetes, and leeches.
17. Elongated feeding structure, often seen in nemerteans for capturing prey.
18. Organism that feeds on dead and decaying organic matter.
19. The ability of an organism to regrow lost body parts.
20. Parasite that lives on the external surface of its host organism.

1. Wave-like muscular contractions used for movement, often seen in nemerteans
2. A close, long-term relationship between two different species, often mutually beneficial.
5. Reproductive organs that produce gametes (sperm and eggs).
6. Phylum of flatworms, including free-living and parasitic species.
8. Possessing both male and female reproductive organs in the same individual.
9. A method of asexual reproduction where an organism splits into two or more individuals.
10. The disturbance of sediments by living organisms, important in nutrient cycling.
13. Phylum of roundworms, with a cylindrical body and a tough cuticle.
14. Internal partitions separating segments in the body of annelids.
16. Phylum of ribbon worms with elongated, flexible bodies.