Kingdom Animalia is also known as Metazoa. This kingdom does not contain prokaryotes and all the members of this kingdom are multicellular eukaryotes. They are heterotrophs and they depend on other organisms directly or indirectly for food. Most of the animals ingest food and digest in the internal cavity. Most of the organisms are motile which means they can move independently and spontaneously.
There are around 9 to 10 million species of animals, and about 800,000 species are identified.
Characteristics of the kingdom Animalia
- Complex Eukaryotic cells
- Animals are made up of organised eukaryotic cells from the zygote stage. Cells then gradually differentiate into different tissues to provide specialised structure or functions.
- Tissue Specialisations
- Animals are multi-cellular. Various tissue and organ systems are constructed to provide specialised functions for day-to-day survival of the species.
- Animals are Aerobic
- Aerobic metabolism is the means where animals break down food and acquire energy needed for their functions.
- Sexual reproduction
- The survival of most animal species is accomplished through sexual reproduction.
- Most animals are capable of movement – this property of motion is highly dependent upon the development of a stimulable skeletal-muscular system.
- Varies in Size
- The sizes of animals ranges from a few celled organism to animals weighing many tons.
- Respiration is a gaseous exchange of taking in oxygen and giving out carbon dioxide. This process takes place in organs of respiration.
- Animals ingest food, and digestion takes place in the internal cavity like the digestive system in animals, in primitive animals vacuoles are for digestion.
- Nervous system
- Sensory mechanism and the coordination of the organ systems is carried on by the nervous system. In animals the nervous system comprises of nerve ganglions, or brain, spinal cords and nerves.
- Circulatory system
- The distribution of nutrients, exchange of gases and removal of wastes takes place in the circulatory system. This system comprises of the heart, blood vessels and the blood.
- Excretory system
- Removal of wastes from kidneys.
- Skeletal system
- The skeletal system supports the animal, and provides protection.