Animals which arise from cells arranged in two germ layers
Cnidarian animals like jellyfish and hydra show the presence of two germ layers, and are hence called diploblasts. They show true tissue development and radial symmetry.
Animals that arise from cells arranged in two germ layers are known as diploblastic animals. These animals have two germ layers during early embryonic development, which are the ectoderm and endoderm. The ectoderm gives rise to the outer covering and nervous system, while the endoderm forms the inner lining of the gut and other internal organs. Diploblastic animals lack a middle germ layer called the mesoderm, which gives rise to muscles, connective tissues, and other structures in triploblastic animals. Examples of diploblastic animals include cnidarians (jellyfish, corals, and sea anemones) and ctenophores (comb jellies).
Animals that arise from cells arranged in two germ layers are called diploblastic animals. These animals have two primary germ layers during development: the ectoderm and the endoderm.
The ectoderm is the outermost germ layer, which gives rise to structures like the skin, nervous system, and sensory organs of the animal. It is responsible for forming the protective covering and nervous tissues.
The endoderm, on the other hand, is the innermost germ layer, which gives rise to the digestive tract and associated organs like the liver, pancreas, and lungs. It is responsible for forming the lining of the digestive system and certain internal organs.
Unlike diploblastic animals, most animals, known as triploblastic animals, have three germ layers. These additional layers, called the mesoderm, are located between the ectoderm and endoderm. The mesoderm gives rise to structures like muscles, bones, blood vessels, and reproductive organs.
To determine if a particular animal is diploblastic or triploblastic, you would need to study its embryonic development. This involves careful observation of the early stages of the animal's development, typically under a microscope. By tracking the formation and organization of cells, one can identify if the animal has two germ layers (diploblastic) or three germ layers (triploblastic).