What kind of animals are not found on our planet! Some amaze with their size, some surprise with their habits and lifestyle, others are distinguished by their incredible colors.
But the most striking in body structure are still the sea and ocean inhabitants. Their body shape can be very unusual, as it has a special symmetry that is not typical for terrestrial animals. This is radial symmetry.
Types of body symmetry in animals
All animals can be divided into four groups according to the types of body symmetry:
- Animals with bilateral symmetry (bilaterally symmetrical). This group includes most species of terrestrial animals and a significant part of marine ones. The main feature is the arrangement of the body organs symmetrically relative to one plane drawn through it. For example, the left and right parts of the body, the back and the front.
- Radial symmetry of the body (radial symmetry). Characteristic of the ocean depths. The main feature is the structure of the body in such a way that several imaginary lines can be drawn through its central axis, relative to which they will be located symmetrically. For example, the rays of starfish.
- Animals with an asymmetrical body shape. When symmetry is not characteristic at all, the shape constantly changes depending on conditions environment or from the movement of an animal. Typical example -
- Complete lack of symmetry. Such organisms include sponges. They lead an attached lifestyle, can grow across the substrate to different volumes and have absolutely no definite symmetry in their body structure.
Each listed group of organisms derives a certain benefit from its structure. For example, bilateral animals can freely move straight while turning to the sides. Animals with radial symmetry are able to catch prey from different directions. It is convenient for asymmetrical organisms to move around and adapt to environmental conditions.
Radiation symmetry: what is it
Basic distinctive feature animals with radial symmetry is their unusual shape bodies. They are usually dome-shaped, cylindrical, or shaped like a star or ball.
Many axes can be drawn through the body of such organisms; relative to each of them there are two completely symmetrical halves. This device allows them to have a number of advantages:
- They move freely in any direction, controlling all directions around them.
- The hunt takes on a larger scale as the prey is felt around the entire body.
- The unusual shape of the body allows it to adapt to the surrounding landscape, blend into it and become invisible.
Radial symmetry of the body is one of the main adaptations for certain classes of animals in the ocean biocenosis.
Characteristics of radial symmetry of the body
The history of the emergence of such a device as radial symmetry of the body goes back to the ancestors of animals. They were the ones who led a completely sedentary, motionless lifestyle and were attached to the substrate. They benefited from such symmetry, and they gave it a start.
The fact that now many actively swimming animals still have radial symmetry indicates that it has not been reduced in the course of evolution. However, its direct purpose this feature no longer fulfills.
The meaning of radial symmetry
Its main purpose in ancestral forms, as well as in modern ones leading an attached lifestyle, is to provide protection from attacks by predators and to obtain food.
After all, animals with radial symmetry were not able to protect themselves, having run away from a predator, they could not hide. Therefore, the only option for protection was to sense the approach of danger from any side of the body and respond in time with protective mechanisms.
In addition, getting food for yourself when you lead a sedentary lifestyle is quite difficult. And radial symmetry allows it to detect the slightest food sources around the entire body and quickly respond to them.
Thus, the radial symmetry of the body gives extremely important mechanisms self-defense and food for the animals that have it.
Animal examples
There are many examples of animals that have radial symmetry. Their huge species and numerical diversity adorns the sea and ocean bottoms and water columns, allowing people to admire the intricacy of nature and the beauty of the underwater world.
What animals have radial symmetry? For example, such as:
- sea urchins;
- jellyfish;
- holothurians;
- brittle stars;
- dartertails;
- hydra;
- sea stars;
- ctenophores;
- fixed polyps;
- some types of sponges.
These are the most common examples of body radial symmetry in animals. There are other animals, little studied, and perhaps not yet discovered at all, which are characterized by this feature of their physique.
Coelenterates
This type of animal includes three main classes, common feature representatives of which is that they are all animals with radial symmetry. The life cycles are dominated by either the stage of a free-swimming jellyfish or the stage of a polyp attached to the substrate. There is one hole, it performs the functions of the oral, anal and genital. Poisonous substances are used for protection
- Hydroid. Main representatives: hydras, hydrants. They lead an attached lifestyle and, like all coelenterates, have two layers in their body structure: ectoderm and endoderm. The middle layer is a gelatinous substance of a watery composition - mesoglea. The body shape is most often goblet-shaped. The main part of life is spent in the polyp stage.
- Jellyfish (scyphoid). The main representatives are all types of jellyfish. The body shape is unusual, in the form of a bell or dome. They are also two-layered animals with radial symmetry. The main part of life is spent in the stage of a freely moving jellyfish.
- Corals (polyps). Main representatives: sea anemones, corals. The main feature is the colonial lifestyle. Many corals form entire reefs from their colonies. Single forms also occur, these are different types actinium. The jellyfish stage is not characteristic of these animals at all, only the polyp stage.
In total there are approximately 9,000 species of representatives of this type of animal.
Echinoderms
What other animals have radial symmetry? Of course, everyone knows and very beautiful, unusual and bright echinoderms. This type has about 7 thousand species of these amazing representatives of marine fauna. There are five main classes:
- Holothurians resemble worms, but still have radial symmetry. Brightly colored, they move reluctantly along the seabed.
- Brittle stars - resemble starfish, but are distinguished by higher mobility and poor color - white, milky and beige.
- Sea urchins - may have regular, needle-shaped exoskeleton, or may not have needles. The body shape is almost always close to spherical.
- Starfish are five-, eight-, or twelve-rayed animals with pronounced radial symmetry. They are very beautifully colored, lead a sedentary lifestyle, crawl along the bottom.
- Sea lilies are sessile beautiful animals and have the shape of a radial flower. They can separate from the substrate and move to places richer in food.
The lifestyle can be either mobile or attached (sea lilies). The body is two-layered, the mouth opening serves as the anal and genital openings. Quite durable, limestone, beautifully decorated with colored patterns.
The larvae of these animals have bilateral symmetry of the body, and only adult individuals grow the rays to radiality.
Ctenophores
Most often they are small animals (up to 20 cm), which have an absolutely white, translucent body, decorated with rows of combs. This type of animal is considered one of the most ancient. Ctenophores are predators, eating crustaceans, small fish and even each other. They reproduce very intensively.
In the structure of the body, a third mouth opening appears on the upper part of the body; they lead a free-swimming lifestyle. The most common types are:
- beroe;
- Platyktenidae;
- gastrodes;
- Venus' belt;
- Bolinopsis;
- tjalfiella.
Their radial symmetry, like the radial symmetry of some species of coelenterates, is weakly expressed. The body shape resembles a bag or an oval.
Generalization
Thus, radial symmetry of the body is the prerogative of aquatic animals that lead a sedentary or attached lifestyle and gives its owners a number of advantages in hunting prey and evading predators.
To the question What is radial symmetry? given by the author Katya Chernykh the best answer is Beam (radial) symmetry is a form of symmetry in which a body (or figure) coincides with itself when the object rotates around a certain point or line.
As a rule, in multicellular animals, the two ends (poles) of a single axis of symmetry are unequal (for example, in jellyfish, the mouth is located on one pole (oral), and the tip of the bell is on the opposite (aboral) pole. Such symmetry (a variant of radial symmetry) in comparative anatomy is called uniaxial-heteropole. In a two-dimensional projection, radial symmetry can be preserved if the axis of symmetry is directed perpendicular to the projection plane. In other words, the preservation of radial symmetry depends on the viewing angle.
Radiation symmetry is characteristic mainly of coelenterates. Coelenterates, both sessile and pelagic (jellyfish), are characterized by radial axial symmetry, in which similar parts are located around the axis of rotation, and this symmetry can be of a very different order depending on the angle at which the animal’s body should be rotated in order to the position coincided with the original one. Thus, 4-, 6-, 8-ray symmetry and more can be obtained, up to symmetry of the order of infinity. Radiolarians have radial-axial symmetry with identical poles, or, as they say, homopolar. In coelenterates, there is heteropolar axial symmetry: one pole of symmetry bears the mouth and tentacles (oral), the other (boral) serves for attachment (polyp stage), or in swimming forms carries a sensory organ (ctenophores), or not armed with anything (jellyfish).
Some jellyfish develop a stalk on this aboral side for attachment to underwater objects (Lucernariida). Violation of radial-axial symmetry occurs when the number of tentacles decreases or the shape of the oral cavity, esophagus and branches changes digestive system. The number of tentacles can be reduced to one (Mopobrachium), and then their radial arrangement is replaced by a bilateral one. The pharynx can be flattened, and then bilateral symmetry also results; this is also facilitated by the formation of siphonoglyphs in the pharynx (a groove along the pharynx).
The greatest complication of radial-axial symmetry is observed in ctenophores, where, in addition to 8-ray symmetry, 4-ray and bilateral symmetry is observed in the arrangement of individual parts of the body and organs. This is a very significant point, since most zoologists derive both stems of higher animals, both protostomes and deuterostomes, from ctenophore-like ancestors.
Heteropolar radial-axial symmetry is quite consistent with the lifestyle of coelenterates - a motionless existence in an attached position or slow swimming using jet propulsion.
On the other hand, from complex type radial-axial symmetry of ctenophores, one can move to bilateral symmetry, or, as they say, mirror image symmetry, the only plane of symmetry of three-layered animals, symmetry of rapid movement, with the development of the anterior end of the body, with a central brain cluster and the main sensory organs, dorsal and abdominal , right and left sides of the body.
..more details - . berl. ru/article/nauka/cimmetria_u_givotnyh.htm here (remove about)
When comparing representatives of different systematic groups, it seems that they are unusually diverse. However, the differences between animals are not endless.
As was shown by Charles Darwin, many related groups of animals descended from one ancestral line. “Going down” from the tips of the branches of the animal family tree to the branching nodes and ultimately to the trunks, we perceive the commonality of many organisms in their structural plans. Scientists have established several such plans, which accommodate a large number of options. It should be remembered that the building plan is something common to many groups. Variants are particulars, details that are the first to catch the eye and often mask the animal’s belonging to a certain type. The commonality of structural plans indicates homology - similarity based on the relatedness of organisms.
With few exceptions, animals are distinguished by a symmetrical structure. There are two types of symmetry - radial, or radial, and bilateral, or bilateral. Both of these types are simultaneously found only in invertebrate animals. Vertebrates are always bilateral.
In the body of a radially symmetrical animal (Fig. 1), one can distinguish the main longitudinal axis, around which the organs are located in a radial (radial) order.
The order of radial symmetry depends on the number of repeating organs. If there are 5 identical organs around this imaginary main axis, then the symmetry is called five-ray, if 4 - four-ray, etc. As a result, through the body of the animal (its center) it is possible to draw a strictly defined
the number of planes of symmetry by which the body is divided into two halves, mirror images of each other. Radial symmetry has two varieties: radial-radial and radial-axial symmetry. Radial symmetry is observed in many organisms suspended in water (a number of unicellular organisms, as well as colonial unicellular organisms and some multicellular colonies), in which the habitat is the same on all sides.
Radial-axial symmetry is observed in several groups of invertebrates (coelenterates, echinoderms, etc.), which are characterized by the fact that they lead (or their ancestral forms led) an attached lifestyle. This means that a sedentary lifestyle contributes to the development of radial symmetry (Dogel, 1981). The biological explanation for this structure is as follows. Sessile animals are attached to the substrate with one pole (aboral), while the other pole (oral), on which the mouth opening is located, is free. This pole is placed in identical conditions on all sides in relation to environmental factors. That's why various organs develop equally on radially located parts of the body, and the main axis connects both poles.
Bilateral symmetry of an animal's body is characterized by the fact that only one plane of symmetry can be drawn through its body, dividing it into two equal (mirroring each other) halves - left and right. Bilateral symmetry arose in animals during the transition of their planktonic ancestors to life and movement on the bottom. Moreover, in addition to the anterior and posterior ends of the body, their dorsal (dorsal) and ventral (ventral) sides began to differ. Examples of bilaterally symmetrical animals include worms, arthropods, and all chordates, including humans.
The biological explanation for bilaterality is as follows.
When transitioning to a crawling (at the bottom) lifestyle, two sides of the animal - abdominal and dorsal - fall into different conditions in relation to environmental factors. One end of the body becomes the front and the mouth opening, as well as the sensory organs, move towards it. This is understandable, since when moving, this end is the first to encounter sources of irritation. The main axis of the body runs from the anterior pole, where the mouth is, to the posterior pole, where the anus is located. The side parts are in equal position. A single plane of symmetry can only be drawn by “cutting” the animal into left and right halves along the main axis of the body.
symmetry of similarity;
radial symmetry
Reflection is the most famous and most often found type of symmetry in nature. The mirror reproduces exactly what it “sees,” but the order considered is reversed: your double’s right hand will actually be his left, since the fingers are arranged in the reverse order.
Mirror symmetry
can be found everywhere: in the leaves and flowers of plants, architecture, ornaments. The human body, if we talk only about its appearance, has mirror symmetry, although not quite strict. Moreover, mirror symmetry is characteristic of the bodies of almost all living creatures, and such a coincidence is by no means accidental.
Anything that can be divided into two mirror-like halves has mirror symmetry. Each of the halves serves as a mirror image of the other, and the plane separating them is called the plane of mirror reflection, or mirror plane. This plane can be called a symmetry element, and the corresponding operation can be called a symmetry operation.
Rotational symmetry.
The appearance of the pattern will not change if it is rotated at a certain angle around its axis. The symmetry that arises is called rotational symmetry. In many dances, figures are based on rotational movements, often performed only in one direction (i.e. without reflection), for example, round dances.
The leaves and flowers of many plants exhibit radial symmetry. This is a symmetry in which a leaf or flower, turning around the axis of symmetry, turns into itself. On cross sections radial symmetry is clearly visible in the tissues that form the root or stem of a plant. The inflorescences of many flowers also have radial symmetry.
Reflection at the center of symmetry.
An example of an object of the highest symmetry, characterizing this symmetry operation, is a ball. Spherical forms are quite widespread in nature. They are common in the atmosphere (fog droplets, clouds), hydrosphere (various microorganisms), lithosphere and space. Spores and pollen of plants, drops of water released in a state of weightlessness on spaceship. At the metagalactic level, the largest spherical structures are spherical galaxies. The denser a galaxy cluster, the closer it is to a spherical shape. Star clusters are also spherical.
Translation, or transfer of a figure over a distance.
Translation, or parallel transfer of a figure over a distance, is any unlimitedly repeating pattern. It can be one-dimensional, two-dimensional, three-dimensional. Translation in the same or opposite directions forms a one-dimensional pattern. Translation in two non-parallel directions forms a two-dimensional pattern. Parquet floors, wallpaper patterns, lace ribbons, paths paved with bricks or tiles, crystalline figures form patterns that have no natural boundaries.
Screw turns.
Translation can be combined with reflection or rotation, which creates new symmetry operations. Rotation by a certain number of degrees, accompanied by translation to a distance along the axis of rotation, generates helical symmetry - symmetry spiral staircase. An example of helical symmetry is the arrangement of leaves on the stem of many plants.
The sunflower head has shoots arranged in geometric spirals, unwinding from the center outward. The youngest members of the spiral are in the center.
In such systems one can notice two families of spirals unwinding in opposite sides and intersecting at angles close to straight lines.
Following Goethe, who spoke about the tendency of nature towards a spiral, we can assume that this movement is carried out along a logarithmic spiral, each time starting from a central, fixed point and combining translational movement (stretching) with a rotation.
Symmetry of similarity.
To the symmetry operations listed above, we can add the symmetry operation of similarity, which is a kind of analogy of translations, reflections in planes, rotations around axes with the only difference being that they are associated with the simultaneous increase or decrease of similar parts of the figure and the distances between them.
The symmetry of similarity, realized in space and time, is everywhere manifested in nature on everything that grows. It is the growing forms that include the countless figures of plants, animals and crystals. The shape of the tree trunk is conical, highly elongated. The branches are usually located around the trunk in a helical line. This is not a simple helix: it gradually tapers towards the top. And the branches themselves become smaller as they approach the top of the tree. Consequently, here we are dealing with a helical axis of similarity symmetry.
Living nature in all its manifestations reveals the same goal: every living object repeats itself in its own kind. The main task of life is Life, and the accessible form of existence lies in the existence of individual integral organisms.
Radial symmetry in nature.
Taking a close look at the nature around us, you can see the commonality even in the most insignificant things and details. The shape of a tree leaf is not random: it is strictly natural. The sheet seems to be glued together from two more or less identical halves, one of which is located mirror-image relative to the other. The symmetry of a leaf stubbornly repeats itself, be it a caterpillar, a butterfly, a bug, etc.
Flowers, mushrooms, trees, and fountains have radial symmetry. Here it can be noted that on unpicked flowers and mushrooms, growing trees, a gushing fountain or a column of vapor, the planes of symmetry are always oriented vertically.
Thus, we can formulate in a somewhat simplified and schematized form common law, clearly and everywhere manifested in nature: everything that grows or moves vertically, i.e. up or down relative to the earth's surface, is subject to radial symmetry in the form of a fan of intersecting symmetry planes. Everything that grows and moves horizontally or obliquely in relation to the earth's surface is subject to bilateral symmetry, the symmetry of a leaf. Not only flowers, animals, easily moving liquids and gases, but also stones are subject to this universal law. This law affects the changing shapes of clouds. On a windless day, they have a dome-shaped shape with more or less clearly defined radial symmetry.
Ryzhov Ilya
During execution, I established a mathematical connection natural phenomena, found out that the human eye is much more pleasant to look at symmetrical things. After doing research various sources information about symmetry, came to the conclusion that nature is arranged in accordance with the laws of symmetry. All living things in nature have the property of symmetry. Symmetry can be seen among flowers and on the leaves of trees. Man used the property of symmetry inherent in living nature in his achievements: he invented the airplane, created unique architectural buildings. And the man himself is a symmetrical figure
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I would like to present to your attention my design and research work on the topic “Symmetry in living nature” (slide No. 1)
The purpose of my work:Show the connection between symmetry and nature, consider what types of symmetry are found in animals and flora. (slide No. 2) Tasks: Give an idea of symmetry in nature; through the concept of “symmetry” to reveal the most important connections between the phenomena of symmetry and living nature; to prove that we are really surrounded symmetrical objects; show the significant role of symmetry in living nature (slide No. 3) To solve the problems, I conducted my own research, studying material from the media, the Internet, specialized literature, analyzing appearance insects, plants, birds, animals, humans. Nominated hypothesis : Is symmetry really found in living nature and what role does it play? (slide No. 4)
Subject of study(slide No. 5)
Symmetry as a pattern.
Object of study
Definition of the concept and types of symmetry, symmetry and its role in the life of plants, animals and humans.
Relevance of the projectis due to the fact that symmetry surrounds a person, finding its manifestation in both living and inanimate nature. An explanation of the laws of symmetry is important for understanding beauty, harmony, and life. The results of the project will be of interest to middle and primary school students. (slide No. 6)
Exists a large number of definitions of the concept “symmetry”, but I chose this one. (slide No. 7)
SYMMETRY - proportionality, proportionality, uniformity in the arrangement of parts
What role does symmetry play in the world around us? (slide number 8)
Symmetry pleases the eye and inspires poets; it allows living organisms to better adapt to their environment and simply survive.
In mathematics are considered different kinds symmetry.
Types of symmetry (slide No. 9)
A) Bilateral (two-sided) axial symmetry
(Latin bi - two, two, lateralis - side).
b)Radiation symmetry(= radiant, radial)
V) Central symmetry
G) Mirror symmetry
Nature is an amazing creator and master. All living things in nature have the property of symmetry. (slide No. 10,11)
Symmetry characteristic of representatives of the animal world is called bilateral symmetry
If you look at any insect from above and mentally draw a straight line (plane) in the middle, then the left and right halves of the insects will be the same in location, size, and color. After all, we have never seen that a beetle or a dragonfly, or any other insect, had paws on the left that were closer to the head than on the right, and the right wing of a butterfly or ladybug would be more than the left. This does not happen in nature, otherwise insects would not be able to fly.
Bilateral symmetry is characteristic of most multicellular animals and arose in connection with active locomotion. Insects and some plants also have bilateral symmetry. For example, (slide No. 12) the shape of a leaf is not random, it is strictly natural. It’s like it’s glued together from two more or less identical halves. One of these halves is located in a mirror image relative to the other. Botanists call this symmetry bilateral or double lateral. But it is not only the tree leaf that has such symmetry. Mentally, you can cut an ordinary caterpillar into two mirror-like equal parts. A beautiful butterfly with bright colors flew by. It also consists of two identical halves. Even the spotted pattern on its wings obeys this geometry. And a bug peeking out from the grass, a flashing midge, a torn branch - everything obeys the symmetry of the leaf. Everything that grows and moves horizontally or obliquely in relation to the earth's surface is subject to bilateral symmetry, i.e. axial. The same symmetry is preserved in organisms that have the ability to move. Although without a specific direction. Such creatures include starfish and urchins.
The human body is built on the principle of bilateral symmetry. (slide number 13) Most of us view the brain as a single structure; in reality, it is divided into two halves. These two parts - two hemispheres - fit tightly to each other. The left hemisphere controls the right side of the brain, and the right hemisphere controls the left side. Physical symmetry of the body and brain does not mean that the right side and the left are equal in all respects. It is enough to pay attention to the actions of our hands to see the initial signs of functional symmetry.
Our own mirror symmetry is very convenient for us, it allows us to move straight and turn right and left with equal ease.Everything that grows and moves horizontally or obliquely in relation to the earth's surface is subject to bilateral symmetry.
Another type of symmetry: (slide 14,15)
Radial or radial (in mathematical language this symmetry is called rotational symmetry)
Radial symmetry is characteristic, as a rule, of animals leading an attached lifestyle. Such animals include hydra. If you draw an axis along the body of the hydra, then its tentacles will diverge from this axis in all directions, like rays. If you look at the petals of a chamomile, you can see that they also have a plane of symmetry. Thus, we can conclude that everything that grows or moves vertically down or up relative to the earth’s surface is subject to radial symmetry.
From everything we have studied, we can formulate a general law that is clearly and universally manifested in nature. Everything that grows or moves vertically, that is, up or down relative to the earth's surface, is subject to radial symmetry. Interestingly, the human eye also has radial symmetry. (Slide No. 16) The next type of symmetry is central (slide No. 17)
There is no concept of a center of symmetry in Euclid’s Elements, but the 38th sentence of Book XI contains the concept of a spatial axis of symmetry. The concept of a center of symmetry was first encountered in the 16th century.
Another type of symmetry is mirror (slide No. 18)
Mirror symmetryis well known to every person from everyday observation. As the name itself indicates, mirror symmetry connects any object and its reflection in a plane mirror. One figure (or body) is said to be mirror symmetrical to another if together they form a mirror symmetrical figure (or body). It is important to note that two bodies that are symmetrical to each other cannot be nested or superimposed on each other. So glove right hand cannot be worn on left hand. Symmetrically mirrored figures, for all their similarities, differ significantly from each other. To verify this, just hold a sheet of paper up to the mirror and try to read a few words printed on it; the letters and words will simply be flipped from right to left. For this reason, symmetrical objects cannot be called equal, so they are called mirror equal. I carried out research, the purpose of which is to find out the reasons that determine symmetry in the plant kingdom. I placed the bean sprouts in two clear tubes. I placed one tube in a horizontal position and the other in a vertical position. A week later I discovered that as soon as the root and stem grew beyond the horizontal tube, the root began to grow straight down and the stem upward. I believe that the downward growth of the root is due to gravity; upward growth of the stem is influenced by light. Experiments carried out by astronauts on board orbital station under conditions of weightlessness, showed that in the absence of gravity, the usual spatial orientation of seedlings is disrupted. Consequently, in conditions of gravity, the presence of symmetry allows plants to take a stable position. Studying popular science literature, in order to identify symmetry in some of the studied plants and animals, I received: (slide No. 20)
This research topic helps to understand the connection between mathematics and biology and the world around us. (slide No. 21) I established a mathematical connection between natural phenomena and found out that it is much more pleasant for the human eye to look at symmetrical things. After researching various sources of information about symmetry, I came to the conclusion that nature is arranged in accordance with the laws of symmetry. All living things in nature have the property of symmetry. Symmetry can be seen among flowers and on the leaves of trees. Man used the property of symmetry inherent in living nature in his achievements: he invented the airplane, created unique architectural buildings. And the man himself is a symmetrical figure.Therefore, symmetry did not arise by chance - perhaps symmetrical objects are easier to perceive for living beings.
While working on the project, I touched the mysterious mathematical beauty. Mathematics is a language, the language of nature. Without knowing the language, you cannot understand the beauty of the world around you