Animals are organisms that make up the kingdom Animalia in Biology. Characteristics that distinguish it from other creatures that are eukaryotic (have a nuclear membrane) and multicellular. There are 2 types of animals, namely vertebrates and invertebrates. Almost all animals reproduce sexually, but some reproduce asexually such as Hydra and Cnidaria. Animals are categorized into ecological groups depending on how they obtain or consume organic matter, including carnivores, herbivores, omnivores, detritivores, and parasites.