Kingdom Animalia

Description: Animals are a group of complex, motile eukaryotic organisms that populate many areas of the earth. They are very diverse in form and ecological niche. As animals grow, their body plans become fixed until they no longer mature physically, unlike many other kingdoms of organisms.

Body Plan: All animals are multicellular organisms, with highly differentiated tissues that become more complex as the animal matures from the embryonic stage to maturity.

Divergent Event: Animals most likely evolved from a flagellated eukaryotic organism, which became differentiated from organisms similar to it due to the position of its flagellum, and became more complex over millions of years, eventually forming the first sponges, which are a primitive type of animal organism.

Metabolism: All animals are heterotrophs, and ingest other organisms to gain sustenance. Specifically, carbon compounds are digested through cellular respiration, which takes in oxygen and releases carbon dioxide.

Digestion: Some animals possess intracellular digestion, such as jellyfish, hydra and corals. Extracellular digestion takes place in animals such as humans, who use enzymes to digest materials and then absorb them directly into the body's cells.

Circulation: Animals that are vertebrates possess a closed circulatory system, in which blood circulates throughout the body. An animal’s heart is a chunk of muscular tissue that expands and contracts to pump blood through its veins.

Respiration: Different types of animals possess different types of respiratory systems. Aquatic animals possess gills, while land animals possess lungs, and still others possess both. Furthermore, all animals undergo cellular respiration to release carbon dioxide and produce ATP.

Nervous: Animals possess both a brain and ganglia that accompany it, which make up their nervous systems. Common parts of animal brains include the cerebellum, prefrontal cortex, and the hippocampus.

Reproduction: Animals engage in both sexual and asexual reproduction. Dogs, for example, are bred through sexual reproduction, but there are also some species that undergo parthogenesis (self-fertilization of egg cells by a female), such as the whiptail lizard, a species entirely composes of females.

Examples: Humans, or Homo sapiens, are a prime example of animals. We are complex, two legged vertebrates that consume other organisms to gain energy, like other animals.

A green sea turtle, or Chelonia mydas, is also an example of an animal, albeit one that swims underwater. As reptiles, turtles are cold blooded and lay eggs to reproduce. Despite their relative dissimilarity from humans, however, both are certainly animals