The kingdom Animalia has a broad variety of members, such as the earthworm, the lion, and the jellyfish, who belong to different classes and are, therefore, placed all over the spectrum regarding complexity. By comparing the various body systems of these classes, it can be concluded that the Mammalia class is the most advanced.
The earthworm, which is a member of the Clitellata class, is very primitive in regards to its respiratory system. The earthworm does not have a specialized system for respiration, but rather relies on diffusion to absorb oxygen. It does so by keeping its outer layer of skin moist so the oxygen can pass through easily. The jellyfish, a member of the Scyphozoa class, acts similarly and absorbs oxygen easily through its skin. This method, used by both the earthworms and jellyfish, gets oxygen into the body but isn’t always the most efficient way. The lion, a mammal, has a more advanced way of respiration and has an entire
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The lion has internal, sexual reproduction where the male injects sperm into the female in order to fertilize her eggs. This system helps the lions reproduce the best they can in their natural environments and allows the mother to protect her children while they are developing inside her.The earthworm is a hermaphrodite, which means that it contains both male and female reproductive organs. However, two mates are typically required in order to produce offspring. The two earthworms line up next to each other and exchange sperm, and then a cocoon slides off of each one to envelop the eggs and the new sperm. Jellyfish have external reproduction, where they release the egg and the sperm into the water to meet each other. As they mature the fertilized eggs reproduce asexually by cloning themselves. The methods used by the earthworms and jellyfish both offer an opportunity for predators to eat the offspring before they can