Lophotrochozoa - Summary Life on Earth PDF

Preview

Summary

Evolution ...

Description

Lophotrochozoa (clade) composed of two phyla: trochozoand and the lophophores. Trochozoans produce trochophore larvae. They have 2 bands of cilia around the middle. they have apical organ on the top-(sensing), and band or prototroch (band of cilia for swimming and eating) around the middle. Include the Annelida, Nemertea, Mollusca, Sipuncula. Lophophorata are united by the presence of the lophophore. A fan of ciliated tentacles surrounding the mouth.

Trochozoans with the trochophore larvae. Annelids (Oligochaetes=earth worms, leeches) (Myzosotoids-looking at the larval stages!) Characteristics of annelids: Segmented worms. coelomic cavity (formed by the solid masses of mesoderm splitting), like all protostomes. They have spiral cleavage, again, like all protostomes. Trochophore larvae. Molluscs Gastropods: snails, the mantle secretes calcium carbonate to produce a protective shell. Some such as slugs have lost their shell through evolution and produce slime instead. Advantageous in low Calcium environments. Cephalopods: largest invertebrate is the giant squid! Also have v high cognitive development of all invertebrates! Characteristics of Molluscs: radula (rasping tinge, eating). Mantle (epidermal covering “cloak”). Shell secreted by mantle. Gills under the mantle. Muscular foot. Coelomic cavity (mesoderm splits). Spiral cleavage and trochophore larva (like all protostomes!). Both the phyla below lack a coelomic cavity. But use spiral cleavage and do have a trochophore larvae. Nemertean (ribbon worms). Noe coelomic cavity, move by small ripples of muscular contractions by using cilia on the surface. Flat worm: again, lack the large fluid filled coelomic cavity. Parasitic-problem globally! Rotifers shows similarities with the trochophore larvae-ciliated

Lophophorata are united by the presence of the lophophore. Composes two phyla Phoronida. Have the feeding lophophore structure Brachiopods-look like a mollusc but instead have a VENTRAL and DORSAL shell. Inside the shell has the feeding structure of the lophophore ciliated structure. Bryozoans also For a long time, people considered that the lophophore larvae were closely related to DEUTROSTTOMES! But based on molecular data they are protostomes, closely related to the annelids and molluscs. The defining feature of the Lophophorata is the lophophore feeding structure, however they do not have the same larvae as the Trochozoan larvae. The trochophore larvae as stated above are characterised by the presence of the apical cilia and the prototroch. BUT Lophophorata do have larvae of Corse! There are similarities between the Lophophorata larvae and the trochophore larvae: SEGMENTS AND SETAE. There is still much uncertainty regarding the relationship WITHIN the Lophotrochozoa. We know that each of the phyla belong within the Lophotrochozo but how they relate to each other is still hotly debated....