Organisms and the Animal Life Cycle
Humans have been animals too, from time immortal. It is amazing how much they have lost over the years from their evolutionary history. Most people don’t realize that what they eat and how they dress actually determines much of what they will be like as an adult. Even animals that are considered to be “tricks” or “costumes” have a lot more going on under the hood than meets the eye.
Humans are multicellular organisms, eukaryotes, in the kingdom Animalia. With the exception of a few plants and animals, all other living things are in a class called Multicellular organisms. In this kingdom, animals are single-celled, breathe air, can multiply, reproduce, and live both in water and on land. The classification of animals is even further divided into a Kingdom of living unicellular organisms and a Kingdom of multicellular organisms.
Each animal has a unique reproductive system, and all reproductive systems have certain characteristics. All animals have a genitalia or “zooid,” including male and female reproductive organs, which are present in both sexes. The genitalia are generally separated by a narrow entrance (hypoplasia) into the body cavity. There is generally a paired penis and a female vulva. The urethra, or tube leading to the outside of the body, is enclosed by the paired labia.
Not all animal species have vocal cords. The most popular among them are marsupials and birds. Dolphins, whales, crocuses, and some placental mammals make sounds that are unique to their species. Birds have the most sophisticated singing mechanisms, producing sounds ranging from a high-pitched squawking to a soft chirping to produce a variety of tones and voices.
A majority of the animals that exist today have evolved from more simple versions of themselves. A few examples of such creatures are fishes, amphibians, and worms. Insects share many of their characteristics with reptiles and arachnids. Most insects are wingless, although some, such as dragonflies, possess fully functioning wings.
The animal kingdom has various taxonomic classifications, with classification based on similarities of anatomy and genetic features between species. Most experts divide the animal kingdom into two major categories: Protista and Bacteria. The first group includes such creatures as fishes, amphibians, crustaceans, mollusks, and insects. The second group consists of bacteria, yeasts, protozoa, other unicellular organisms, plants, fungi, and Archaea. The classification of the animal phylum refers to the class of cells that an organism belongs to.