ALL REGARDING EVOLUTION

ALL REGARDING EVOLUTION

What is Evolution?

Evolution is the gradual change occurring in living organisms over a long duration. This is a very slow-going process through which the development of organisms is achieved. All the stages in changes that occurred in various components ranging from stars and planets in space to the biosphere present on the Earth should be included in the study of evolution. The Formation of new species due to changes in specific characters of several generations of living organisms as a response to natural selection is called evolution.

3.5 billion years ago, life had been non-existent on the Earth. In the beginning, there may have been only simple types of organic and inorganic compounds that may have been formed from those. Complex compounds like proteins and nucleic acids may have formed over a long period from those simple compounds. The First primitive type of cells may have been formed from the mixture of different types of organic and inorganic compounds. The Number of those cells may have increased at the cost of surrounding chemicals. There may have been some differences among those cells and according to the principle of natural selection, some may have shown good growth and some may have perished which could not adjust to the surrounding.

At present, crores of species of plants and animals with huge diversity regarding shape and complexity are present on the Earth. Animal diversity ranges from the unicellular Amoeba and Paramoecium to man and giant whale. The plant diversity consists of various species ranging from unicellular  Chlorella to the huge Banyan tree. Life exists on Earth from the equator to both the Poles. Organisms are present at all places like air, water, land, rock, etc. Humans have shown curiosity about the origin of life and reasons for such a great diversity in life present on the Earth since ancient times. Different theories about the origin and evolution of life have been proposed till today of which the theory of ‘Gradual Development’ of living organisms is accepted.

Theory Of Evolution

According to this theory, the first living material (protoplasm) has been formed in the ocean. In due course of time, unicellular organisms were formed. Gradually, changes occurred in the unicellular organisms from which larger and more complex organisms were found. All those changes were slow and gradual. The duration of all these changes is a must 300 crore years. Changes and development in living organisms had been all round and multi-dimensional and this led to the evolution of different types of organisms. Hence, this overall process is called evolution which is organizational. The progressive development of plants and animals from the ancestors having different structural and functional organization is called evolution.

A Peek into History 

Many philosophers and religious scholars have written their views about the formation of life. There seems to be a thorough discussion over the formation of the Universe, in various cultures like Indian, Chinese, Roman, Greek, etc. Various cultures have noted different types of information about planets, stars, the ‘panchmahabhuta’, living organisms, etc. in the form of poetry, stories, and religious/sacred books.

Evidence of Evolution

Collective thinking upon all the above-mentioned theories implies that evolution is an everlasting process of change. However, it needs proof to prove it. The following are various proofs available in support of the theories mentioned above.

Morphological Evidence

Various similarities like the structure of the mouth, position of eyes, structure of nostrils and ear pinnae, and thickly distributed hairs on the body are seen in animals whereas similarities in characters like leap shape, leaf venation, leaf petiole, etc. occur in case of plants. This indicates that there are some similarities in those groups and hence it proves that their origin must be the same and must have common ancestors.

Anatomical Evidence

If you carefully notice, that there doesn't seem any superficial similarity between the human hand, cat's foreleg, the flipper of a whale, and patagium of the bat. similarly, the use of each of those structures is different in the respective animals. However, there is a similarity in the structure of bones and Bony joints in the organs of each of those animals. This similarity indicates that those animals may have a common ancestor. 

Vestigial organs

 degenerate or underdeveloped useless organs of organisms are called vestigial organs. In living organisms, the sudden development of new tissues or organs for living in a changing environment is not possible. instead, existing organs undergo gradual changes. Mostly, a specific structure in a body is useful in certain situations. However, the same structure under different situations may become useless or even harmful. search structure began to degenerate under such situations as per the principle of natural selection. it takes thousands of years for a structure to disappear. Sach organs are seen in different phases of disappearance in different animals. such organs,   though non-functional in certain organisms, may be functional in other organisms i.e. it is not vestigial in other organisms.

 appendix, which is useless to humans, is a useful and fully functional organ in ruminants. Similarly, muscles of ear pinna, which are useless to humans, are useful in monkeys for a moment of the ear pinna. Various vestigial organs like tailbone  (coccyx), wisdom teeth, and body hair are present in the Body of a human being.

 Paleontological Evidence 

A question may arise in your mind: Which organisms existed millions of years ago? How can we tell this? now this secret has been hidden in the earth. A large number of organisms get buried due to disasters like flood, earthquake, volcano,  etc.  remnants and Impressions of such organisms remain reserved underground. These are called fossils. The study of fossils is an important aspect of the study of evolution.

 Carbon consumption of animal plant stores after and since then, only the decaying process of C-14 occurs continuously. In the case of dead bodies of plants and animals, instead of remaining constant, the ratio between c14 and see 12:00 changes continuously as C-12 is non Radioactive. The time passed since the death of a plant or animal can be calculated by measuring the radioactivity of c14 and ratio of c14 to  C12  present in their body. This is a ‘carbon dating’ method. It is used in paleontology and Anthropology for determining the age of human fossils and manuscripts. Once the age of fossils is determined by such a technique, it becomes easy to reduce the information about other erstwhile organisms. it means that vertebrates have slowly originated from the invertebrate.

Scientists

 The carbon dating method is based upon the radioactive decay of naturally occurring c14 and it is developed by  Willard Libby.

 He has been awarded the Nobel Prize (1960) for this invention. The age of the materials determined by this method is published in the journal 'Radiocarbon’.

Connecting links

 some plants and animals show some morphological characters by which they can be related to two different groups; hence they are called ‘ connecting links’. Ex. in peripatus, characters like the segmented body, thin cuticle, and parapodia like organ are present.  Similarly, duck-billed Platypus lay eggs like reptiles but show a relationship with mammals due to the presence of mammary glands And hairs.  lungfish performs respiration with lungs irrespective of being fish. These examples indicate that mammals evolved from reptiles and amphibians from fishes.

Embryological evidence

Comparative study of embryonic development stages of various vertebrates are done and it shows that all embryos show extreme similarities during initial stages and those similarities decrease gradually. Similarities in initial stages indicate the common origin of all the animals.