Bio1331 Animals - Evolution - Deuterostomes And The Evolution Of Chordates (Lecture Six)

Sea stars have the ability to regenerate lost body parts, including their arms. When a sea star loses an arm, it can grow a new one through a process called regeneration. This is possible because sea stars have specialized cells in their arms called pluripotent cells, which have the ability to develop into any type of cell needed for regeneration. These cells can divide and differentiate into the necessary tissues and structures to form a new arm. Therefore, the statement "Sea stars can undergo regeneration if they lose an arm" is true.

The notochord in Chordates provides skeletal support. This structure is a flexible rod-like structure that runs along the length of the body, providing support and rigidity. It serves as a precursor to the vertebral column in vertebrates, forming the basis for the development of the backbone. The notochord also plays a role in signaling during embryonic development, guiding the formation of the central nervous system. However, its primary function is to provide support to the body.

One of the three major clades of deuterostomes is echinoderms. Echinoderms are a group of marine animals that include starfish, sea urchins, and sea cucumbers. They are characterized by their radial symmetry and unique water vascular system.

All chordates have a notochord, which is a flexible rod-like structure that provides support and serves as the basis for the development of the backbone in vertebrates. This characteristic is a defining feature of chordates, which include animals such as fish, reptiles, birds, and mammals. The notochord is present in the early stages of development in all chordates, although it may be replaced by the vertebral column in some species as they mature. Therefore, it is correct to say that all chordates have a notochord.

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Sea urchins and humans share a common ancestor, so they have some genes in common. Out of the 23,000 genes in sea urchins, 7,707 of them are shared with humans. This suggests that there are certain genetic similarities and evolutionary relationships between sea urchins and humans.

The correct developmental pattern of a deuterostome is radial cleavage, indeterminate. Radial cleavage refers to the pattern of cell division in which the cells divide parallel or perpendicular to the polar axis, resulting in a radial arrangement of cells. Indeterminate cleavage means that each cell produced by cleavage has the potential to develop into a complete organism. In deuterostomes, such as echinoderms and chordates, the early embryonic cells are totipotent, meaning they have the ability to develop into any cell type in the organism. Therefore, the correct answer is radial cleavage, indeterminate.

Echinoderms are bilaterally symmetrical as larvae.