Final answer:
Lophophorates, such as flatworms and annelids, have simple excretory systems like flame cells and nephridia, respectively, which function to propel waste out through excretory pores. Insects use Malpighian tubules for waste excretion.
Step-by-step explanation:
Lophophorates are aquatic invertebrates that may possess excretory structures less complex than those found in vertebrates. In lophophorates and other invertebrates, simple excretory organs have evolved, such as flame cells, nephridia, and Malpighian tubules. For instance, flatworms, which belong to the phylum Platyhelminthes, use protonephridia as an excretory mechanism, consisting of a network of tubules with flame cells that propel wastes out through excretory pores. Similarly, earthworms (annelids) use nephridia, which are a bit more evolved and capable of tubular reabsorption before excretion. Some insects excrete metabolic wastes via Malpighian tubules, indicating the diversity and adaptation in excretory systems within different invertebrates.