What is organic evolution?
The development of the present complex creatures on earth was due to the changes in the simple beings found in the beginning according to the situation and environment. This change in the living world is called organic evolution. In simple words, biological evolution literally means to know about the hidden object that changes from time to time. The branch of biology that deals with the origin of living things. The study of karmic changes in their generations is called biological evolution. Bio-evolution is a slow gradual change.

Definition of Organic Evolution
"Biological evolution is the change in the genetic makeup of a species in a population as a result of responding to environmental changes." The branch of biology that studies the history of the origin and ancestors of organisms and the gradual changes that have occurred over time. It is called organic evolution or evolution.

Theories Of Organic Evolution
Many types of ideas were presented for the explanation of biological evolution, but most of them could not get scientific recognition due to lack of proper evidence. French scientist J.B. The origin of species by natural selection or Darwinism was the first biological Scientific recognition has been received regarding development.


lamarckism theory
Markism was founded by the French natural scientist J.B. The outline of Lamarck (Jean Baptiste Lamarck) was revealed only in 1801. He first published the theory in 1809, his ideas of biological evolution in his book Philosophic Zoologique. This is called Lamarckism or the theory of inheritance of acquired characters.

Theory-

  • According to Lamarck, there is a direct effect of the change of environment on the structure, physiology, their behavior. Due to the changed environment, the use of organs of organisms is more or less.
  • The organs that are used more become more developed, and those which are not used, they gradually decline.
  • The changes that take place in the body of an animal due to the direct effect of the environment or due to less or more use of organs are called acquired characters.
  • The acquired traits of animals are heritable, i.e. passed from one generation to another through reproduction.
  • Due to this continuously, after a few generations, their anatomy changes and a new species develops.

Lamarckism was later strongly opposed by many scientists. According to opposing scientists, acquired traits are not inherited. To confirm this, the German scientist Weismann, by cutting the tail of a rat for 21 generations, demonstrated that the tail is present in every generation in the offspring of a rat with a severed tail. The muscles of the hands of the blacksmith become strong due to hammer, but the quality of such strong muscles is not passed on to his offspring.

Organisms in which sexual reproduction takes place. Generative cells are formed in their gonads or gonads of the gonads. Other cells of the body are called somatic cells. Changes that occur in somatic cells due to the influence of the environment are not transmitted to the offspring. This is because the changes that take place in somatic cells do not take place in them as well as in germ cells.

Darwin's theory of biological evolution

"Charles Darwin" Charles Darwin's ideas related to organic-evolution and natural selection are called Darwinism, this theory was given by two English scientists Alfred Russell Wallace and Charles Robert (Charles Robert Darwin) jointly propounded. The two scientists worked independently to draw similar conclusions. The famous English scientist named Charles Robert Darwin expressed the explanation of biological evolution in his book The Origin of Species. His theory of biological evolution is called Origin of species by natural selection or Darwinism.

Theory-

  • His theory is based on interesting observations made during his famous sea voyage.
  • He made this sea voyage from 1831 AD to 1836 AD, a British ship going to South America, HMS. Beagle (H.M.S. Beagle).
  • According to Darwin, organisms have the ability to produce as many children as possible through reproduction.
  • The food and habitat for the living beings on this earth are fixed in comparison to the high rate of reproduction in each organism. Therefore, there is a struggle among the living beings for their existence. The struggle for existence takes place with other species as well as with nature or the environment.
  • No two organisms are exactly alike in nature. There must be some differences between them.
  • Due to the abundance of variations in the organisms, the struggle for life begins. In the struggle for life, only those living beings are the fittest, those who have the most meritorious qualities. Organisms with unqualified qualities perish.
  • In other words, nature selects the organisms with the fittest and favorable variations and destroys the unfit and unfavorable variations.
  • Successful members in the struggle for life live longer and contribute to the continuation of their inheritance.
  • This is what an English philosopher Herbert Spencer called the survival of the fittest in the context of social evolution and this is what Darwin called natural selection in the context of biological evolution.

He said that nature also generates new castes by encouraging successful members through elections. That is why Darwinism is called Theory of natural selection. In 1858, Darwin and Wallace published their work jointly under the name Natural Selectionism.

Drawbacks of Charles Darwin's theory-

  • Darwin did not explain evolution on the basis of heredity.
  • According to Darwin, variations were responsible for the origin of new species, but according to scientists, small differences cannot lead to the origin of new species.
  • Scientists have also rejected Darwin's sex selectionism.
  • When organisms with inherited traits mate with each other, which do not have these traits, the effect of the traits is not reduced by the union of these two. Darwin could not explain it.
  • Nature selection did not specify the specificity of any part due to which some species were destroyed.

Neo-Darwinism Theory

Neo-Darwinism is commonly used for the integration of Charles Darwin's theory of evolution by natural selection with Gregor Mendel's theory of genetics. Neodarwinism is also called modern synthetic theory. Neo Darwinism is the result of the interaction of the following processes.

1. Gene Mutation: Those changes in the sequence of the number or configuration of nucleotides in the DNA molecule of a gene are called gene mutations which change the expression of normal genes.

2. Variation due to change in structure and number of chromosomes: A change in the structure of chromosomes occurs due to change in the number or configuration of the genes attached to the chromosome called chromosomal aberration. it is said.

3. Genetic recombination: In the process of sexual reproduction, meiosis occurs at the time of gamete formation. During separation, new gene configurations are formed as a result of mutual gene exchange (crossing over) in the chromosomes, from which variations arise in the organisms. The recombination of genes also takes place by hybridization.

4. Isolation: When different populations of the same species are separated due to geographical reasons, then according to the environment in their gene structure and new variations are accumulated by gene mutation, chromosomal aberration and polyploidy which are generation- It keeps on increasing from generation to generation.

Mutation Theory
A gene is a sequence of nucleotides in the DNA that contains the coded information that ultimately leads to the synthesis of proteins. These are the basic and functional components of heredity. It is derived from the Greek word genus. DNA located on chromosomes (D.N.A.) The microscopic structures that hold and transfer genetic traits from one generation to another are called genes. Gene is the basic physical unit of heredity. That is, in this we have information about our genetic characteristics like what will be the color of our hair, what will be the color of the eyes or what diseases we can have. And this information resides in the element present in the center of the cells, it is called DNA. When there is a permanent change in the DNA of a gene, it is called a mutation. It can be caused by a defect in cell division, or by ultraviolet radiation, or by chemical substances or viruses.

Comparative composition of organisms

  1. Homology: Organs which may be quite dissimilar due to their use in different functions but have similarity in their basic structure and embryonic process are called Homologous Organs. There is also similarity in blood and nervous structure of homologous organs. Examples of homologous organs - Wings of insects and wings of birds, wings of insects and wings of bats etc.
  2. Analogy: Organs which appear similar because of their use in similar functions, but differ in their basic structure and embryonic process, are called analogous organs. This similarity proves convergent evolution, i.e., evolution from different ancestors in the same direction.
  3. Vestigial organs: Some obvious but underdeveloped and inactive unusable organs or parts of organs found in evolved animals are called vestigial organs. Such as feathers of ostrich, feathers of emu and cassivari of Australia, feathers of kiwi of New Zealand, feathers of dodo (currently extinct) etc. The feathers in their ancestors were fully developed, but due to environmental influence and due to their loss of usefulness, they are in the form of residual organs in the direction of gradual disappearance in the course of evolution. Appendix in humans is also an example of a residual organ.
  4. Connecting link: Those species which are the boundary line between their less developed species and more developed higher order species, that is, a combination of the characteristics of both (low and high) species, are called connecting species. They provide solid evidence of organic evolution.

Example:-

  1. Euglena: The association of protozoa, chlorophyll-containing plants and animals as a coordinator.
  2. Proterospongia: phylum Protozoa, unicellular members, origin of sponges from their ancestors.
  3. Neopilina: Invertebrates more evolved from members of the phylum Mollusca, Annelida, as a phylum of Mollusca and Annelida.
  4. Peripatus: The phylum Auropoda, it is the link between Annelida and Auropoda and proves the evolution of Auropoda from Annelida.
  5. Archaeopteryx: Presently extinct, it was a link between reptiles and birds. This bird was a class animal because its wings were more developed.
  6. Prototheria: Subclass of low-order mammals, currently it has three categories - Echidina, zaglossus, and Ornithorhynchus These reptiles and mammals are found in Australia and New Guinea.

Glossary related to genetics and biological evolution:

Word Meaning
Homozygous When alleles or alleles of a trait are the same, it is called homozygous. For example, tall plant (TT), dwarf plant (tt) etc.
Genotype The genetic structure of an organism is called the genotype or genotype of that organism.
Sex chromosome The chromosomes involved in sex determination are called sex chromosomes. These chromosomes are different in both male and female plants or animals.
Autosomes These chromosomes are found equally in males and females. These chromosomes are found in somatic cells.
Gene The short segment of DNA that contains the genetic material is called a gene. The word gene was first used by Johansen in 1909 AD.
Genome The genetic material found in a chromosome is called a genome.
Plasmagene If genes outside the chromosomes are present in the cytoplasm, they are called plasmagenes.
Mutation Mutations are discrete genetic changes that occur suddenly and are transmitted from generation to generation.
Back Cross If a pure or hybrid type is crossed from the genotype of the first generation to the genotype of the paternal generation, then it is called cross back cross.
One gene one enzyme theory An enzyme is synthesized by a gene. This principle was discovered by Beadle and Tatum in 1948.
Vasectomy The sterilization of men is called vasectomy.
Tubectomy Sterilization of women is called tubectomy.
Euthenics In this, the development of high genetic traits of human beings is studied through good upbringing and education.
Factors The trait that is passed on from generation to generation is called a factor.
Klinefelter's syndrome It has three sex chromosomes instead of two and usually XXY. Due to the presence of an extra X-chromosome in it, testes are present and sperms are not produced in them. Such men are impotent.
Hereditary characters The traits which are passed from parent to child from generation to generation are called genetic traits.
Dihybrid cross When two plants are crossed on the basis of two pairs of opposite traits, it is called a dihybrid cross.
Sex determination The process of determining sex in individuals is called sex determination. Genetics plays an important role in determining the sex of an individual.
Acquired character The changes that take place in the body of an animal due to the direct effect of the environment or due to less or more use of organs are called acquired traits.
Heterozygous In homologous factors, if both the factors are opposite to each other i.e. one is dominant and the other is recessive, then that pair is called heterozygous or hybrid. E.g. Hybrid tall plant (Tt) 4. Phenotype
Linkage When two different traits are bound on the same chromosome, they are inherited together rather than independently. Morgan called this phenomenon linkage. This is an exception to Mendel's law.
Genetics The study of the transfer of various traits from parent to child and the causes and laws related to it is called genetics. The term genetics was first used by W Watson in 1905 AD.
Indiogram When homologous pairs of identified chromosomes of a karyotype are arranged in descending order of length and are shown diagrammatically on a certain scale, it is called endogram.
Color blindness It is also called Daltonism. People suffering from this are unable to distinguish between red and green. It is a sex related disease which is passed from one generation to another through heredity.
Turner's syndrome These are situations in which only one X-chromosome is found. Their stature is small and the genitals are rudimentary. The thorax is flattened and the genitals are absent or rudimentary. It is impotent.
Phenylketonuria The accumulation of phenylalamine in the nervous tissue of children causes mental deficiency. In this disease, there is a deficiency of the enzyme phenylalamine hydroxylase, which converts phenylalamine into an amino acid called tyrosine.
Organic evolution Bioevolution is that branch of biology, under which the history of the origin and ancestors of organisms and the gradual changes that took place in them from time to time are studied.
Hornologous organ Such parts of animals living in different environments, which are similar in terms of structure and origin, but perform different functions according to their environment, are called homologous organs.
Analogous organ Organs found in different animals, which are different from each other in terms of structure and origin, but perform the same type of function, are called heterologous organs.
Germinal variation Variation arising due to change in the structure or number of chromosomes or genes of the generative cells is called genetic variation. It is also called genetic variation, as it is transmitted from one generation to another.
Somatic variation The variation arising due to the effect of climate and environment, type of food available, interaction with other living organisms etc. is called vegetative variation. This type of variation is not inherited from one generation to another. Such variations are acquired.
Aneles Characteristic factors expressing different contrasting forms of the same trait are called alleles or allelomorphs. For example, the color red, green and yellow of a flower are denoted by R, G, Y respectively. Similarly tall (T) and dwarf (t) are also pair alternatives.
Gene Exchange (Crossing over) During the synapsis action of the prophase stage of meiosis, the non-sister chromatids of homologous chromosomes undergo mutual exchange of corresponding genetic eggs, leading to the formation of new combinations of linked genes. Through this the qualities of mother and father are exchanged and the qualities of both come in the child.
Test Cross If the genotype of the first generation (F1) is crossed with the genotype of the paternal generation (P) (pure or hybrid = TT or Tt), it is called a back cross, but when the genotype of the first generation (F1) is crossed with the genotype of the paternal generation (P). If the genotype hybrid (hybrid) is crossed with recessive such as tt, then it is called test cross.
Eugenics It is the branch of genetics under which the study of the improvement of human society through genetic laws is done. Sir Francis Galton first named a new branch called eugenics. That is why Galton is called the father of eugenics.
Haemophilia It is also a sex linked disease in humans. A person suffering from this disease continues to flow blood continuously even after a long time of injury. Hence it is also called Bleeder's disease. This disease is often found in men. This disease is also passed from one generation to another by inheritance.
Sickle cell anaemia In this disease, due to lack of oxygen, the hemoglobin of RBCs shrinks to the shape of a sickle. This disease is caused by a dormant gene. In this disease, due to lack of oxygen, RBCs burst into the shape of a sickle, causing hemolytic anaemia.
Down's syndrome In this, the chromosomes of the 21st pair are three instead of di, that is, the number of chromosomes in such a person is 47. A person with this syndrome is of short stature and retarded. In this the genitals are identical but the male is impotent. It is also called Mongoloid Idiocy.
Chromosomes A tangled fine thread-like structure is found in the nucleus, which is called chromatin network. The chromatin reticulum breaks down during cell division to form thread-like structures called chromosomes or chromosomes. The number of chromosomes is fixed for an organism of a particular species. Chromosomes are in the form of short and thick rod-like structures. Genetic traits are passed from one generation to another by chromosomes. That is, chromosomes are the carriers of genetic properties. Chromosomes are made up of DNA and protein molecules. Gametes have only one copy of different chromosomes which is called haploid or genome. Somatic cells have two such copies, which are called diploid chromosomes.

Now practice related questions and see what you learnt?

☞ Biological Evolution GK Questions and Answers 🔗

Read also:

Biological Evolution FAQs:

Evolution is supported by fossil evidence, which documents the existence of now-extinct past species closely related to present-day species.

Genetics is one of the branches of biology that studies heredity, genetic variation and heredity in organisms. It was first discovered by the scientist Gregor Mendel in the late 19th century.

The major threatened species are classified by the IUCN into six classes. Which includes categories like extinct, extinct in the wild, critically endangered, endangered, vulnerable etc.

Paleontology branch of biology deals with extinct organisms. Paleontology is the branch of geology that deals with the remains of animals and plants from geological ages that are now found only in the rocks of the earth's crust.

The end product of nitrogen exchange in aquatic organisms is ammonia, which is the primary product of protein metabolism. Fishes excrete ammonia into the water with the help of their gills.

  Last update :  Wed 14 Jun 2023
  Post Views :  7456
  Post Category :  Biological Sciences