Final answer:
Lophophorates, part of the Lophotrochozoa superphylum, have a closed circulatory system, excretory system with tubular nephridia, complete digestive system, and a brain. These features, along with molecular evidence, define them as a clade of protostomes closely related to annelids and mollusks.
Step-by-step explanation:
The student is asking about the internal systems present in lophophorates, which are part of the superphylum Lophotrochozoa. Lophophorates include organisms that have either a lophophore feeding structure or exhibit a trochophore larvae stage. The lophophore is a set of ciliated tentacles around the mouth used for feeding, while trochophore larvae are free-swimming and characterized by two bands of cilia. Organisms placed within this group demonstrate various internal systems, such as:
- A closed circulatory system, which is seen in some advanced lophotrochozoans like cephalopods.
- An excretory system consisting of tubular nephridia, which serve to filter waste from the body fluids.
- A complete digestive system that separates the mouth from the anus, unlike the simpler gastrovascular cavities found in creatures like flatworms and jellyfish.
- A brain and associated nervous system, which is indicative of cephalization and more complex behaviors.
Lophotrochozoa is a clade of protostomes, evident through molecular studies such as analysis of rRNA and protein sequences. These studies have helped clarify the evolutionary relationships within this group, confirming that lophophorates are more closely related to annelids and mollusks, rather than deuterostomes as previously thought.