What is an animal?

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What is an animal?

Animal: The animal is every eukaryotic organism belonging to the animal kingdom. Animals are expendable beings that can not make their own food. There are between 9-10 million species of which only 800,000 species are identified, Animals are in the sea, some are in fresh water. Land contains the smallest number of animals. The animals vary in size. There are tiny animals, whose bodies are made up of a few cells, and there are animals that weigh many tons, such as the blue whale. Most animals are side-by-side, few are radically similar, and primitive animals are asymmetric. [1]

The internal structure of animal bodies: The animal's body consists of cells, similar cells form tissue, and tissues that perform similar functions form members, consisting of different body organs, including: [2]

*** Structural device: Provides support and protection of the body, consisting of either bones, cartilage, or pores
Gastrointestinal system: Digests digestion of food, and different digestive systems different types of animals, for example, their digestive system consists of mouth, salivary duct, esophagus, stomach, intestines and large intestine, pancreas, liver and rectum, The amoeba, its digestive system is just a food gap on the cell membrane, and sponge has special structures to remove plankton from water.The circulatory system distributes oxygen and food to all parts of the body, and saves it from waste. It consists of the heart, blood vessels, blood, and some animals have an open circulation device, ie the exchange of materials and the disposal of waste is carried through cell membranes. The circulatory system is closed and is more efficient; for the presence of special organs to remove blood from waste, such as liver, kidney, and some animals consists of the heart of two rooms like birds, and the heart of mammals consists of four rooms.Respiratory system: In animals, gases are exchanged by the lungs in animals that live on land, such as mammals. Air passes through the nose and mouth to the alveoli. Breathe by gills.

*** Output device: The kidneys that rid the body of waste.

*** Immune system: protects the body from pathogenic organisms, and consists of skin, glands, and blood cells.

*** Reproductive system: It is the organ responsible for reproduction, and consists of ovaries in females, and testes in males.

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