In our article we will consider the characteristics of the animal kingdom. Representatives of this systematic unit are very diverse and widespread in nature. These include more than 5 million species, including humans.
The animal kingdom: general characteristics and diversity
By what signs can you determine whether the body belongs to animals? First of all, this is a heterotrophic mode of nutrition, active movement in space, a developed nervous system, a pronounced reaction to a stimulus. These are the main characteristics of the animal kingdom.
The number of species of these representatives of the organic world is several times higher than combined plants and mushrooms. Among animals, there are microscopic unicellular organisms, as well as real giants. For example, a humpback whale, whose body length approaches 15 meters.
Habitat
In nature, animals can be found absolutely everywhere. Their main habitat is ground-air. They run on the ground, fly, crawl in a wide variety of conditions: from hot deserts to the cold tundra. A large number of animals live in water bodies. These are fish, whales and dolphins. In some species, life is only partially related to water: walruses, seals, elephants, seals. Soil inhabitants are traditionally considered many types of worms. But mole rats and moles also live here. Their organs of vision are underdeveloped due to their adaptability to the lack of sunlight.
The characterization of the animal kingdom (Grade 7 studies this topic in detail in a zoological course) would be incomplete without representatives whose habitat are other organisms. They are characterized by a parasitic lifestyle and high fecundity. These are flukes, tapeworms, echinococcus, roundworm, trichinella, pinworm and other types of worms.
Food
The consumption of prepared organic substances is the main characteristic of the animal kingdom. This feature is decisive in matters of classification. For example, the unicellular organism of chlamydomonas actively moves with the help of flagella and a photosensitive eye. But he is a representative of the plant world, as he is capable of photosynthesis.
According to the type of heterotrophic nutrition among animals, the following groups are distinguished:
- Predators - lurk and attack their victims.
- Parasites - eat at the expense of other organisms.
- Saprotrophs - consume residues or waste products of other species.
- Phytophages - prefer only products of plant origin.
Motion
Active movement of the body in space is another important characteristic of the animal kingdom. Unicellular species carry it out using special structures. They are called organelles of movement. In ciliates, these are numerous cilia, in green euglena - flagellum. But the amoeba protea does not have a constant body shape. Its cytoplasm constantly forms temporary protrusions - pseudopods, or pseudopodia.
In multicellular organisms, movement is carried out by more complex structures. So, the intestinal cells have skin-muscle cells. Reducing, they change the shape and position of the body in space. The covers of the worms are represented by a skin-muscle bag. It consists of integumentary epithelium, as well as one or more layers of muscles. Highly organized animals have a musculoskeletal system. This is a combination of the skeleton and muscles. Differentiation of the latter allows animals to carry out the most complex movements.
Height
The increase in body size of most animals occurs only during a certain time of their life. Such growth is called limited. For example, the formation of a person ceases by about 25 years. Unlimited growth is also a characteristic of some representatives of the animal kingdom. It is characteristic of crocodiles, turtles, some species of fish.
In insects, crustaceans and reptiles, growth is accompanied by molting. The fact is that their covers are not capable of stretching. And only dropping the cuticle and chitin allows the body to increase in size.
Reproduction Methods and Development
Most animals are characterized by sexual reproduction. It occurs with the participation of germ cells - eggs and sperm. The process of their merger is called fertilization. Depending on the place in which it occurs, fertilization can be external or internal.
In the first case, the germ cells merge outside the body of the female. This feature is characteristic of amphibians and fish. Since fertilized eggs are not protected from adverse environmental conditions, females throw thousands of eggs into the water. In the second case, both fertilization and subsequent development are carried out inside the female body. Therefore, such individuals are more likely to survive, and their number is less.
In rare cases, animals can breed by budding. For example, freshwater hydra. First, a small protrusion forms on her body, it increases in size, acquires the features of an adult body, and then goes on to independent existence. Some species of crustaceans breed parthenogenetically. This is the development of an organism from an unfertilized egg.
The way of individual development is another characteristic of the animal kingdom. These are qualitative changes in organisms. With direct development, an animal is born, which is a copy of the adult body. It is characteristic of birds, reptiles, mammals.
If an individual appears that is significantly different from an adult, then this method of development is called indirect. For example, frog larvae resemble fish fry and actively swim in water. The same can be said of butterflies. Their larvae, called caterpillars, eat the leaves of plants, and adults - the nectar of flowers.
The best
A brief description of the animal kingdom would be incomplete without getting to know the most unusual of them. The record holder in size is a blue whale, reaching a length of more than 30 meters. The weight of this giant is also impressive - 190 tons. And which animal is the tallest? Even the student will answer that it is a giraffe. The most surprising is the fact that with a growth of about 6 meters in its cervical region there are only 7 vertebrae. The field mouse and chinchilla have the same amount.
The title of the fastest on the planet is rightfully occupied by a cheetah, antelope, killer whale, peregrine falcon bird and sailfish. In their habitat no one will steal them. Among the strongmen, the rhinoceros beetle is in the lead, which is capable of lifting weight 850 times its own mass.
So, the main characteristics of the representatives of the animal kingdom are:
- distribution in all habitats;
- heterotrophic nutrition;
- active movement in space;
- development of the musculoskeletal and nervous systems;
- limited growth.