Multicellular organisms: plants and animals

Despite the diversity of unicellular organisms, more complex organisms are much better known to humans. They represent the most numerous group, which includes more than one and a half million species. All multicellular organisms have certain common characteristics, but at the same time are very different. Therefore, it is worthwhile to consider separate kingdoms, and in the case of animals - and classes.

Common Properties

The main feature that separates single-celled and multicellular organisms is the functional difference. It arose in the course of evolution. As a result, cells of a complex body began to specialize, merging into tissues. The simplest ones use only one for all the necessary functions. In this case, plants and fungi are traditionally taken into account separately, since the animals and plant cells also have significant differences. But they should also be taken into account in studying this topic. Unlike the simplest, they always consist of a multitude of cells, many of which have their own functions.

Class of mammals

Of course, the most famous multicellular organisms are animals. Of these, in turn, are mammals. This is a highly organized class of chordates, which includes four and a half thousand species. Its representatives are found in any environment - on land, in soil, in fresh and salt water bodies, in the air. The advantages of multicellular organisms of this type over others in the complex structure of the body. It is divided into the head, neck and trunk, a pair of front and rear extremities, and also a tail. Thanks to the special arrangement of the legs, the body is raised above the ground, which ensures the speed of movement. All of them are distinguished by a thick enough and elastic skin with sweat, greasy, fragrant and mammary glands located in it. Animals have a large skull and complex musculature. There is a special bulging membrane, called the diaphragm. Animal modes of movement include various actions - from walking to climbing. The heart consists of four chambers and supplies arterial blood to all organs and tissues. For breathing, the lungs are used, for allocation - the kidneys. The brain consists of five sections with several large hemispheres and a cerebellum.

Class of birds

Answering which organisms are multicellular, it is impossible not to mention birds. These are highly organized warm-blooded creatures capable of flying. There are more than nine thousand modern species. The importance of a multicellular organism of this class is incredibly great, since they are maximally distributed, and therefore participate in the economic activities of people and play an important role in nature. From other creatures of birds distinguishes several basic properties. They have streamlined bodies with forelimbs, transformed into wings, and rear, which are used as a support. Birds are characterized by dry skin without glands, with horny formations, known as feathers. The skeleton is thin and durable, with air cavities providing its lightness. The muscular system provides the ability for walking, running, jumping, swimming, lasagna and two types of flight - soaring and waving. Most species can travel long distances. The birds have no teeth and there is a goiter, as well as a muscle department, grinding food. The structure of the tongue and beak depends on the specialization of food.

Class of reptiles

It is worth mentioning and this type of creatures, representing multicellular organisms. Animals of this class were the first to become terrestrial vertebrates. At the moment about six thousand species are known. The skin of the reptiles is dry and devoid of glands, it covers the stratum corneum, periodically descending in the process of molting. A strong ossified skeleton is distinguished by strengthened shoulder and pelvic belts, as well as developed ribs and thorax. The digestive tract is long enough and clearly differentiated, the food is captured with the help of jaws with sharp teeth. The respiratory organs are represented by the lungs with a large surface, bronchi and trachea. The heart consists of three chambers. Body temperature is determined by the habitat. The organs of secretion are the kidneys and the bladder. Fertilization is internal, eggs are deposited on land and protected by a leathery or shell shell.

Class of amphibians

Enumerating multicellular organisms, it is worth mentioning amphibians. This group of animals is ubiquitous, especially common in warm and humid climates. They have mastered the terrestrial environment, but have a direct connection with water. There were amphibians from brutal fishes. The body of the amphibian features a flat form and division into the head, trunk and two pairs of limbs with five fingers. Some also have a tail. Thin skin is distinguished by a multitude of mucous glands. The skeleton consists of many cartilages. Muscles allow you to make a variety of movements. Amphibians are predators, food is digested by the stomach. Respiratory organs are the skin and lungs. The larvae use the gills. The heart is three-chambered, with two circles of blood circulation - this system is often distinguished by multicellular organisms. The kidneys are used for excretion. Fertilization is external, occurs in water, development proceeds with metamorphosis.

Class of insects

Unicellular and multicellular organisms are not the least different, and surprising variety. This type includes insects. This is the most numerous class - it includes more than a million species. Insectability is distinguished by the ability to fly and greater mobility, which is provided by the developed musculature with segmented limbs. The body covers the chitinous cuticle, the outer layer of which contains fatty substances that protect the body from drying out, ultraviolet and damage. Different mouthparts reduce the competition of species, which allows us to constantly maintain a high number of individuals. Small sizes become an additional advantage for survival, as well as a wide range of breeding methods - parthenogenetic, bisexual, larval. Some also differ in polyembryony. The respiratory organs provide intensive gas exchange, and the nervous system with perfect sense organs creates complex forms of behavior, conditioned by instincts.

The Kingdom of Plants

Of course, animals are most common. But it is worth mentioning other multicellular organisms - plants. There are about three hundred and fifty thousand species. Their difference from other organisms is the ability to carry out photosynthesis. Plants act as food for many other organisms. Their cells have solid walls of cellulose, and inside it is chlorophyll. The majority are unable to carry out active movements. Lower plants do not have a division into leaves, stem and root. Green algae live in water and can be of different structure and ways of reproduction. Brown perform photosynthesis with fucoxanthin. Red algae occur even at a depth of 200 meters. Lichens are the next sub-kingdom. They are most significant in soil formation, and are also used in medicine, perfumery and the chemical industry. Higher plants are distinguished by the presence of leaves, root system and stems. The most primitive are mosses. The most developed are trees that can be flowered, two- or monocotyled, and also conifers.

The Kingdom of Mushrooms

It is necessary to pass to the latter type, which can be multicellular organisms. Mushrooms combine the features of plants and animals. More than one hundred thousand species are known. The diversity of cells of multicellular organisms is most pronounced in fungi: they are able to reproduce by spores, synthesize vitamins and maintain immobility, but at the same time, like animals, they can eat heterotrophically, do not carry out photosynthesis and have chitin, which also occurs in arthropods.