The living world can be divided into either five or six kingdoms, the five kingdom system being the more widely used. Many of those kingdoms are occupied with creatures you can't see with your naked eye. Kingdoms Monera and Prostita are single-celled organisms. Fungus has its own kingdom, while kingdom Plantae encompasses plants of all kinds. The larger world of creatures that move, breathe and reproduce is called kingdom Animalia.
Other People Are Reading
Some single-celled organisms and even the gametes of some plants are able to move by means of cilia or flagella. There are some creatures in the animal kingdom that use these mechanisms too, but animals are the only ones that have muscles which are described as being based on contractile proteins. For this reason, animalia can move faster and in many more complex ways than any other biological beings.
Members of kingdom Animalia are heterotrophs, which means that they get their nourishment through other organisms, either directly or indirectly. This is in contrast to kingdom Monera, whose members absorb nutrients from the water around them, and plant life, which get their nutrients through photosynthesis. The presence of an digestive tract is distinctive to animals.
The reproduction of creatures in the animal kingdom is usually done sexually, with differentiated sperm and eggs which form inside the bodies of the mature creatures. They develop, with a few exceptions, in similar stages. After cell division, a zygote forms, followed by a blastula and gastrula. The cells of animals are diploid, which means that they contain two copies of genetic material.
While kingdom Animalia is set apart from kingdoms Monera and Prostita by the fact that they are multicellular, they are set apart from kingdoms Fungi and Plantae because they do not have rigid cell walls. Their cells have organelles and a nucleus but do not have chloroplasts. Animalia are also distinctive because they grow---increase their cell numbers--up until a certain point and then cease to grow anymore.
There are an estimated 9 or 10 million species of animalia on Earth. They range from tiny creatures of only a few cells to massive multi-ton organisms like blue whales, elephants and giant squids. The most prolific members of the animal kingdom are insects. There are far more species of insects than there are species of vertebrates, a group which includes mammals, reptiles, fish, birds and others. Nematodes and mollusks also are extremely numerous.
- 20 of the funniest online reviews ever
- 14 Biggest lies people tell in online dating sites
- Hilarious things Google thinks you're trying to search for