There are several common characteristics shared by all animals such as a bear, snake, jellyfish, spiders and humans. The animal kingdom consists of multicellular eukaryotes. Animal evolution began 600 million years ago with the primitive creature having a basic lifestyle. Over time, they nat me, embryological development and genetic makeup evolved to a more complex creature. Almost all animals have specialized tissue. Those are similar cells such as nervous tissue, muscle tissue, epithelial and connected tissue. Various tissue form organs and variant organs form an organ system. Animals have specialized connective tissue that provide many functions including transport and structural support. Most animals are more tile at least during some stage of their life. They are also heterotrophs or sap probes. They are dependent on autotrophic organisms such as plants. Most animals reproduce sexually. Usually there are vertebrates that have a backbone. Offspring pass through a series of developmental stages. Animal bodies are composed of diploid cells and in the hemploid cells are only present in reproductive structures such as the egg and sperm. Animals without backbone may have some asexual reproductive processes such as budding and fragmentation. That is, a piece can be separated and it can grow into a new individual. Some fish, amphibians and reptiles may exhibit these processes. In this chart you can see the phylogenetic tree of animal is based on morphological, fossil and genetic... Elements are classified according to morphological and developmental characteristics. The shape of the animal body is determined during developmental stage by a body plan. With the exception of sponges the animal body is symmetrical. Most animals have body parts in two planes. Additionally the presence or absence of an internal body cavity during embryological development contributes to an animal's characteristic. Animal bodies may be asymmetrical, radial or bilateral in plan. Asymmetrical animals have no symmetry and are generally no shape such as seen in animals such as a sponge. Radial symmetry can be seen in a jellyfish or sea anemone. The body can be divided in different planes. Bilateral symmetry is seen in humans as well as goat. A vertical plane will cut from front to back and separate into a mirror image. These animals have a left and right hand side. Earlier I mentioned that animals undergo an embryonic development which dictates its appearance. During embryonic development of a hollow cluster of cells, forms and this reorganizes into germ layers. There are three germ layers in bilateral symmetrical animals and two germ layers in radial symmetrical animals. Each layer develops into a specific set of tissues and organs. The three germ layers are ectoderm, misuderm and endoderm. The ectoderm differentiates into the central nervous system, the epidermis and the her. Endoderm develops organs such as stomach liver, lungs and intestines. The misuderm provides red blood cells and bone tissue. Diplor blasts develop with two germ layers and triple blasts with three germ layers. Internal body cavity called as a sealum is formed from the misuderm. As seen in the images of a flatworm, annelids and the nematode each have a body cavity lined by the misuderm tissue, hence they have a gut and a sealum. Protosomes include roundworms, mullusk and arthropods. Develop the mouth part as first opening to the gut. Dutrazone include animals which develop a second opening on the dorsal surface called as the anus. The majority of the invertebrates are protosomes. Sponges are animals of the phylum or a frow. These multicellular with no symmetry and generally a body full of pores and channels to circulate water. They do not have nervous, digestive or circulatory system. They are generally filter feeders, absorb food and adjust them. They also are hemorrhoid diets, meaning no male and female distinction. They do develop into free, living larvae. Liderians contain animals found only in aquatic environments. Include jellyfish, sea animony and hydroids. They all have tentacles with stingy cells that are used to capture prey. Bloody hellmethis includes simplest animals that are bilateral. First appearance of a trioblastic layer. They are generally unsegmented, however mainly flat in appearance. First appearance of the nervous cords and ganglion along with simple organs are present in this growth. Pymetodes are also called as round worms. They generally are parasitic. They have tapered body and both ends and have a complete digestive system. Chyton is also present in the external surface to give its structural strength. They are usually present on the ocean floor and have a diverse life cycle. Sun can be monoacias that is 1-6 and others can be dioscious, meaning having both sexes. They look like long tube. The arthropods have jointed legs and dominate the animal kingdom. Most arthropods have an exoskeleton and have segmented body. They have a head, thorax and abdomen or the trunk area. They have an open circulatory system in which blood floods the internal organs rather than circulation. They do have a primitive respiratory system with trachea used to transport air throughout the body and opening it to the outside called as sphericals for gas exchange. The most predominant marine animals are the molarsk. They have the soft body and very in body forms. They include snail scallops. There are more than 100,000 species of molarsks. They have presence of gills for gas exchange. Some molars have shells. They have a mantle, the organ that secreats the shell. Phylum analysts are segmented worms found in aquatic and terrestrial habitats. They are segmented however they have a protective cuticle on the external surface. They have a close circulatory system with a primitive heart. They also have a primitive kidney and gas exchange occurs across the body surface. Earthworm and leeches are examples of analysts. Echinoderms are generally spiny and include species such as stars, sea cucumbers and sea urtans. They have a pentaradial symmetry and an endoskeleton. These animals have a true gut, a portion of which is modified in a unique water-maskular system. This system allows for gas exchange, nutrient circulation and locomotion.