It is commonly seen that members of a species are largely alike. A horse looks like another horse and a rose Plant Looks Like another rose plant. This is to be natural because only horses can produce more horses, and only rose plants can give rise to rose plants. The resemblance among the individuals of a species has given rise to the aphorism “like begets like''. The aphorism, in a way, implies the continuity of life. It is, however, not absolutely true as the members of a species are seldom exactly alike. The children, also the two-egg twins, often have some individual characters in which they differ from one another and also from their parents. In fact, their differences are as marked as their resemblances. Every living organism has a set of characters by which it can be assigned to a particular Species, and can also be identified from other members of its species.
The scientific study : (i)the mechanism of inheritance by which characters pass from parents to offspring and (ii) the causes of hereditary variation in living organisms related by descent is known as genetics.
What is Heredity?
Genetics is also the study of heredity and heredity is the transmission of characters, resemblances as well as variation, from one generation to the next. It is a biological process where a parent transfers certain genes onto their offspring. These genes are inherited by every child from both biological parents which in turn, expresses specific traits.
Gregor Johann Mendel (Austrian, 1822-1884) was born in a peasant family of Moravia. He received school education mainly by his own hard work and passion for studying. Due to poverty, he became a priest. He was later, in 1847, made an abbot (head) of the Augustinian monastery (religious place) of St. Thomas at Brunn, Austria (now Bruno in the Czech Republic). From here, he went in 1851 to the University of Vienna where his interest in the study was natural history and mathematics. Whilst in Vienna, he became interested in the process of hybridization. His choice of the subjects and his aptitude for hybridization had a significant influence on his later work on inheritance on pea plants.
Meaning of Evolution
Evolutionary biology Is that branch of biology which talks about the word
'evolution'. Now, what exactly is evolution? Evolution means the act of unfolding or unrolling and in simple terms, evolution Is an orderly ‘change' from one form to another. But before we learn about how an organism evolved, we must have an understanding of how that organism originated. Therefore, before teaming ‘evolution of life’, we must learn ‘Origin of Life'.
Origin of Universe
Big Bang Theory
The origin of the universe was the most important phenomenon in the origin of life. And the Big Bang Theory attempts to explain the same. This theory proposes that the universe is very old and its origin took almost 20 billion (20 x 109) years ago. It states that a single huge explosion (i.e., Big Bang) took place in space which was so powerful that it is unimaginable in physical terms. Due to this explosion, the universe expands in volume, and the temperature of the space decreases. Slowly Hydrogen and Hahn gases formed, which condensed due to the gravitational forces present in the surroundings. This all resulted in the formation of billions of galaxies.
Did You Know?
In an Experiment: Pasteur took two flasks that were sterilized by him to make them from the microbes. He made a thick soup of yeast and water in both the flasks. ’. He kept one flask open to the air and curved the neck of another one so that the yeast present in the second flask was not in direct contact with the air. He showed that in the "ask which was open to the air. New living organisms took birth while the absence of life appeared in the flask which did not open to the air. He showed that in pre-sterilized flasks, life did not come from killed yeast in the flask with the curved neck, while in another flask open to the air. new organisms arose from “killed yeast’. The purpose of the experiment was not to show that new organisms arose from the “killed yeast“ but to explain that it was actually the ‘air’ in which living organisms were present inside the flask when it was kept open to air to come inside. On the other hand, the curved neck trapped the microbes from entering inside the other flask thereby preventing their growth inside the flask. Hence, it was proved that life cannot arise from the non-living objects (here killed yeast) and could only arise from pre-existing living organisms.
1. What is the evidence for Evolution?
Many important shreds of evidence are present in our nature which show that evolution has indeed taken place on earth. These pieces of evidence clearly demonstrate that the various new life forms have evolved since the creation of the earth. Some of them are:
(i) Fossils (Palaeontological Evidence)
(ii) Number and nature of fossils in early rocks.
(iii) Distribution of fossils in the successive strata.
(iv) The disparity between the past and the present forms of life.
(v) Missing Links (Transitional Forms).
2. What is biological Evolution?
Biological evolution Is defined as any genetic change in a population that is inherited over several generations. Till now we have discussed the concept of evolution and its different pieces of evidence like fossils, homologous sutures, artificial and natural selection, etc. Now we will be dealing with the theories of evolution put forward by various biologists.
3. What is Speciation?
Speciation is the formation of more than one new species from the existing ones. The crucial episode in the origin of species occurs! when the gene pool of a population Is served from other populations of the parent species and gene flow no longer occurs. Speciation can take place In two modes based on the geographical relationship of a new species to its ancestral species.