Variability in biology is called nothing more than the properties of organisms to acquire new features that would differ from their ancestors, as well as individual states of parental organisms compared to descendants during the period of development of an individual organism. The diversity of traits among members of the same species is also called variability.
Types of variability
The following types of variability are distinguished:
- Non-hereditary and hereditary. In other words, modification and genetic.
- Individual, which is the difference between individual individuals, and group. The latter consists in changes between entire groups of individuals. It can be, for example, populations of animals of the same species. It should be understood that group variability is a derivative of individual and is also a property of living things.organisms acquire new traits.
- Distinguish between non-directional and directional variability.
- Quantitative and qualitative.
Due to the properties of organisms to acquire new features, fundamentally new states arise, which serves as a prerequisite for the subsequent speciation and evolution of the biosphere as a whole. Variability is studied by such a science as genetics. But before proceeding to the analysis of variability in genetic terms, let's repeat what biological life as a phenomenon is for a more complete understanding of the picture.
Properties of living organisms
Substances from the external environment enter the body, providing the vital processes of this organism. Thanks to nutrition, nutrients and water enter this biological system, breathing provides oxygen. The body processes these substances, absorbs some of them, and removes some of them, that is, the process of excretion takes place. Thus, there is an exchange of substances between the organism and the environment. The intake of nutrients with food ensures growth and development, all these processes together are necessary to ensure a very important property of the body - the ability to reproduce.
Any change in environmental conditions immediately causes the corresponding reactions of the body. This is one of the representative indicators of the existence of the properties of organisms to acquire new traits. The main properties of living organisms, namely nutrition, metabolismsubstances, growth, respiration, excretion, reproduction, development, irritability, are factors in the existence of a biological unit.
The growth of living organisms
Growth in biology is called the enlargement of the size of an organism with an increase in its mass. Plants can be in a state of growth for almost their entire life. It is accompanied by an increase in size and the formation of new vegetative organs. Such growth is called unlimited.
The growth of animals is also accompanied by an increase in size - proportionally increase all the organs that form the body of the animal. But new organs are not formed. The property of organisms to acquire new characteristics allows the growth of numerous animals to continue only for a certain period of life, that is, to be limited. Organisms during life not only grow, but also develop, change their appearance, acquire new qualities. Development is called the irreversible natural changes that occur in the body of living beings from the moment of its inception to the end of life. A new quality that appears in plants and animals during development is the ability to reproduce.
Development of living organisms
Development, during which a new organism from birth is similar to an adult animal, is called direct. This development is typical for most fish, birds, and mammals. In some animals, development occurs with amazing transformations. For example, in butterflies, eggs hatch into larvae - caterpillars, which after a while form a chrysalis. On theAt the stage of the pupa, complex transformation processes take place, and a new butterfly emerges from it. Such development is called indirect, or development with transformations. Indirect development is typical for butterflies, beetles, frogs.
Variability in genetics
Genetics is the science of the laws of heredity and variability. Heredity in genetics is called the common property of all living organisms to transmit their signs and features of development to offspring. In turn, variability is the ability of organisms to acquire new features and properties that are different between individuals within a species. It is difficult to discuss genetic concepts without knowing what a gene is. Therefore, let's learn that a gene is a section of DNA, the nucleotide sequence of which carries all the encoded information necessary for the subsequent synthesis of RNA and polypeptides. The gene is also the elementary unit of heredity.
Alleles are different variants of a single gene. They arise one above the other as a result of mutations. Contained in the same loci (areas) of homologous chromosomes.
A homozygote is a biological organism that in its cells in homologous chromosomes contains alleles of a given gene of only one type.
A heterozygote can be called an organism whose cells in homologous chromosomes contain different alleles of a particular gene.
The genotype in genetics is called the generalset of genes in a biological organism. The phenotype, in turn, is a set of such properties of an organism that are the result of the interaction of the genotype and the external environment.
The role of variability in evolution
The phenotype of each particular living being is a consequence of the interaction of the genotype of this organism with the conditions provided by the external environment. An impressive part of the variation in the phenotypes of a population is caused by the difference between the genotypes of its individuals. The synthetic theory of evolution defines evolution as a change in this genetic variation. The frequency of alleles in the gene pool fluctuates, as a result of which this allele becomes more or less common in comparison with other forms of such a gene. The common property of all organisms to acquire new traits arises in part because evolutionary forces operate in such a way that they change the frequency of alleles. The variation disappears when the allele frequency reaches a steady state.
The emergence of variation occurs due to mutations in genetic material, migrations among populations and shuffling of genes, which occurs as a result of sexual reproduction. You have already learned that the ability of organisms to acquire new traits is called variability, but it is also important to know that it can arise from the interchange of genes among members of more than one species, for example, through horizontal gene transfer in bacteria and hybridization in plants. Despite the constant change in allele frequencies due to theseprocesses, most genomes are almost identical in all individuals of the same species. However, even relatively small changes in the genotype can lead to dramatic changes in the phenotype. For example, the difference between the human genome and the chimpanzee genome is only five percent of the entire DNA chain.
