Bio1331 Animals - Evolution - Lophotrochozoans (Lecture Four)

Mollusks have a mantle, which is a fold of tissue that covers the organs of the visceral mass and secretes a hard, calcareous shell. The mantle plays a crucial role in protecting the internal organs and producing the shell, which provides support and protection for the mollusk's body. The mantle also helps with locomotion and respiration in some mollusk species.

The correct answer is "Visceral mass." In mollusks, the visceral mass is one of the three main components of their body. It houses the majority of the organism's internal organs, such as the digestive, reproductive, and excretory systems. The visceral mass is protected by the mollusk's hard outer shell and plays a crucial role in the overall functioning and survival of the organism.

The scientific name for flatworms is Platyhelminthes. This name is derived from the Greek words "platys" meaning flat and "helminth" meaning worm. Flatworms are a phylum of invertebrates that have a soft, flattened body shape. They are characterized by their simple body structure and lack of a body cavity. Platyhelminthes include various species such as planarians, tapeworms, and flukes.

The scientific name for segmented worms is "Annelids". Annelids are a phylum of invertebrates that includes earthworms, leeches, and marine worms. They are characterized by their segmented bodies, which allows for flexibility and movement. The term "annelid" is derived from the Latin word "annellus", meaning "little ring", referring to the rings or segments that make up their body structure.

Lophotrochozoans have a unique feature called lophophores, which is one of the two main characteristics that distinguish them from ecdysozoans. The lophophore is a specialized feeding structure found in certain groups of lophotrochozoans, such as brachiopods, bryozoans, and phoronids. It is a horseshoe-shaped or circular organ with ciliated tentacles that surround the mouth, enabling filter feeding and gas exchange. This feature is not present in ecdysozoans, making it a defining characteristic of lophotrochozoans.

The correct answer is "ectoproct". An ectoproct is another name for a Bryozoan, which is a phylum of small aquatic invertebrates. They are colonial animals that form colonies of interconnected individuals called zooids. The zooids have a hard exoskeleton and a ring of tentacles surrounding a mouth-like opening. Ectoproct is the commonly used term to refer to these organisms.

All protostomes are triploblastic because protostomes are a group of animals that develop from a blastopore, which is the opening of the developing embryo. Triploblastic refers to having three germ layers: the ectoderm, mesoderm, and endoderm. All protostomes, including insects, mollusks, and annelids, have these three germ layers during their development. Therefore, it can be concluded that all protostomes are triploblastic.

Spiral cleavage refers to the pattern of cell division in which the cells divide at an angle to the polar axis of the embryo, resulting in a spiral arrangement of cells. Determinate cleavage means that the fate of each cell is already determined early on in development, meaning that if a cell is removed or damaged, it cannot develop into a complete organism. Therefore, the correct pattern of embryonic development for a protostome is spiral cleavage, determinate.

The correct answer is Lophotrochozoans and Ecdysozoans. These are the two clades of protostomes.