Who lacks mesoderm: a pigeon, a dog, a turtle, or a jellyfish? - briefly
Jellyfish lack mesoderm. Pigeons, dogs, and turtles all possess mesoderm as part of their body structure.
Who lacks mesoderm: a pigeon, a dog, a turtle, or a jellyfish? - in detail
Mesoderm is one of the three primary germ layers that form during the early stages of embryonic development in most animals. It gives rise to various tissues and organs, including muscles, bones, cartilage, blood vessels, and parts of the kidneys. Let's examine which among a pigeon, a dog, a turtle, and a jellyfish lack mesoderm.
Pigeons (Columba livia): Pigeons are vertebrates, belonging to the class Aves. Like all vertebrates, pigeons develop from three germ layers: ectoderm, mesoderm, and endoderm. The mesoderm in pigeons gives rise to essential structures such as muscles, bones, and the circulatory system. Therefore, a pigeon does not lack mesoderm.
Dogs (Canis lupus familiaris): Dogs are also vertebrates, belonging to the class Mammalia. Similar to pigeons, dogs develop from all three germ layers, including mesoderm. The mesoderm in dogs is responsible for forming muscles, skeletal tissues, and the cardiovascular system. Consequently, a dog does not lack mesoderm.
Turtles (Testudines): Turtles are reptiles, another group within the vertebrate class. Like other vertebrates, turtles develop from the three primary germ layers: ectoderm, mesoderm, and endoderm. The mesoderm in turtles contributes to the formation of their shell (carapace), muscles, and circulatory system. Thus, a turtle does not lack mesoderm.
Jellyfish (Phylum Cnidaria): Jellyfish are members of the phylum Cnidaria, which includes animals such as corals, sea anemones, and hydroids. Unlike vertebrates, jellyfish do not develop from three germ layers but instead from two: ectoderm and endoderm. The mesoderm is absent in jellyfish, making them diploblastic organisms. This absence of the mesoderm layer distinguishes them from triploblastic animals like vertebrates, which possess all three germ layers. Therefore, a jellyfish lacks mesoderm.
In conclusion, among the listed animals—a pigeon, a dog, a turtle, and a jellyfish—only the jellyfish lacks mesoderm. This difference highlights the evolutionary divergence between diploblastic (two-layer) and triploblastic (three-layer) organisms.