Origin of Life Questions in English

(N/A) $Abiogenesis$: It refers to the theory that life originated from non-living matter. It is also known as spontaneous generation.
$Biogenesis$: It refers to the theory that life originates from pre-existing living organisms. This concept was experimentally proven by scientists like $Louis$ $Pasteur$.

(N/A) Proteinoids are thermal polymers of amino acids. They are synthesized by heating a mixture of dry amino acids at temperatures ranging from $160^{\circ}C$ to $210^{\circ}C$ for several hours. These structures were proposed by Sidney Fox as potential precursors to the first living cells (protobionts) in the prebiotic environment.

(C) When we look at stars,we are observing light that has traveled across vast distances in space. Because the speed of light is finite $(3 \times 10^8 \ m/s)$,it takes time for the light from distant stars to reach Earth. Therefore,the light we see today left those stars many years ago. Consequently,looking at the stars is equivalent to looking into the past.

(D) According to the Big Bang theory,the universe is estimated to be approximately $20,000$ million years old. This is a standard scientific estimate used in evolutionary biology to provide context for the origin of life and the formation of the Earth.

(D) galaxy is a massive system that is gravitationally bound and consists of stars,stellar remnants,interstellar gas,dust,and dark matter. Therefore,all the given options are components of a galaxy.

(A) The $Big$ $Bang$ theory is the most widely accepted scientific explanation for the origin of the universe.
It suggests that the universe originated from a single,extremely hot and dense point approximately $13.8$ billion years ago and has been expanding ever since.
Abiogenesis refers to the origin of life from non-living matter.
Biogenesis refers to the production of new living organisms from pre-existing living organisms.
Panspermia is the hypothesis that life exists throughout the universe and is distributed by space dust,meteoroids,asteroids,or comets.

(B) According to the Big Bang theory,the universe expanded from a hot,dense state. As the universe expanded,the energy density decreased,which led to a significant drop in temperature. This cooling allowed for the formation of subatomic particles,atoms,and eventually stars and galaxies.

(C) According to the Big Bang theory,the universe expanded and cooled down. During the early stages of the universe,the simplest and most abundant elements were formed through primordial nucleosynthesis. The first gases to be formed were primarily $H_{2}$ (Hydrogen) and $He$ (Helium). These elements provided the raw material for the formation of stars and galaxies.

(C) The Earth is located in the galaxy known as the Milky Way (also called the Akash Ganga). The Milky Way is a barred spiral galaxy that contains our Solar System.

(D) According to the scientific consensus and the $NCERT$ biology curriculum,the Earth was formed approximately $4.5$ billion years ago. This is a fundamental fact in the study of evolutionary biology and the origin of life on Earth.

(A) In the early atmosphere of Earth,there was no ozone layer to block solar radiation. High-energy $UV$ rays from the sun reached the Earth's surface and caused the photolysis (dissociation) of water vapor $(H_2O)$ into hydrogen $(H_2)$ and oxygen $(O_2)$. The lighter hydrogen gas escaped into space,while the oxygen combined with other elements like ammonia and methane to form water,carbon dioxide,and other compounds.

(C) During the early stages of the Earth's formation,the atmosphere was reducing. As free oxygen was produced,it reacted with the abundant hydrogen and methane present in the primitive atmosphere. The reaction of oxygen with hydrogen formed water $(H_2O)$,and its reaction with methane $(CH_4)$ and ammonia $(NH_3)$ led to the formation of carbon dioxide $(CO_2)$ and other complex compounds. Therefore,oxygen combined with hydrogen,methane,and ammonia to form these essential molecules.

(B) According to ancient Greek thinkers,life was transferred to different planets,including Earth,in the form of units called $Spores$. This concept is known as the theory of $Panspermia$.

(D) The theory of $Panspermia$ (also known as $Cosmozoa$) suggests that life exists throughout the Universe and is distributed by space dust,meteoroids,asteroids,comets,or planetoids. According to this theory,life was transferred to Earth from other parts of the Universe in the form of resistant spores or microorganisms. Therefore,the correct option is $D$.

(C) The theory of Spontaneous Generation,also known as abiogenesis,proposed that living organisms could arise spontaneously from non-living matter such as decaying grass,mud,or sweat. This theory was later disproven by experiments conducted by scientists like Francesco Redi,Lazzaro Spallanzani,and Louis Pasteur,who demonstrated that life arises only from pre-existing life (Biogenesis).

(A) Louis Pasteur demonstrated that life arises only from pre-existing life. He used a swan-necked flask experiment to show that in pre-sterilized flasks,life did not come from killed yeast,while in another flask open to air,new living organisms arose from life that was already present in the air. This effectively disproved the theory of spontaneous generation.

(B) The theory of chemical evolution,also known as the Oparin-Haldane hypothesis,suggests that life originated from non-living organic molecules through a series of chemical reactions.
$A.I.$ Oparin (from Russia) and $J$.$B$.$S$. Haldane (from England) independently proposed that the first form of life could have come from pre-existing non-living organic molecules (e.g.,$RNA$,protein,etc.) and that the formation of life was preceded by chemical evolution.
Therefore,the correct option is $B$.

(D) Louis Pasteur successfully demonstrated that life comes only from pre-existing life (Biogenesis) through his famous 'swan-neck flask' experiment.
In this experiment,he used a nutrient broth containing killed yeast to ensure that no pre-existing microorganisms were present initially.
By boiling the broth,he sterilized it,and the long,curved neck of the flask prevented airborne microbes from reaching the broth.
Since no life appeared in the sterilized broth until the neck was broken or tilted,it proved that life does not arise spontaneously from non-living matter.

(C) The theory of spontaneous generation,also known as abiogenesis,proposed that living organisms could arise spontaneously from non-living matter. This theory was permanently discarded after experiments by Louis Pasteur demonstrated that life only arises from pre-existing life (biogenesis).

(C) In $1953$,Stanley Miller and Harold Urey conducted a famous experiment to test the Oparin-Haldane hypothesis.
They created a laboratory apparatus that simulated the conditions of the primitive Earth,which included high temperatures,volcanic storms,and a reducing atmosphere containing $CH_4$,$NH_3$,$H_2$,and water vapor.
By passing electric discharges in this closed flask,they observed the formation of simple amino acids.
Therefore,Miller is the scientist who experimentally demonstrated the chemical origin of life.

(A) In $1953$,Stanley Miller and Harold Urey conducted an experiment to simulate the conditions of the primitive Earth.
They created a closed system containing a mixture of gases like methane $(CH_4)$,ammonia $(NH_3)$,and hydrogen $(H_2)$ in the ratio of $2:1:2$,along with water vapor $(H_2O)$.
To simulate the high-energy environment of early Earth,they maintained a temperature of $800^{\circ} C$ using electrodes to create electric discharges.
This experiment successfully demonstrated the synthesis of amino acids from simple inorganic molecules,supporting the chemical evolution theory.

(D) In $1953$,Stanley Miller and Harold Urey conducted an experiment to test the Oparin-Haldane hypothesis regarding the origin of life.
They created a closed system using a flask containing a mixture of gases that simulated the primitive atmosphere of the Earth.
The mixture consisted of methane $(CH_{4})$,ammonia $(NH_{3})$,hydrogen $(H_{2})$,and water vapor $(H_{2}O)$ in the ratio of $2:1:2:1$ respectively.
Therefore,all the gases mentioned in the options were part of the mixture used in the experiment.

(B) Stanley Miller and Harold Urey conducted an experiment in $1953$ to test the Oparin-Haldane hypothesis regarding the origin of life.
They created a closed system containing $CH_4$, $NH_3$, $H_2$, and water vapor at a temperature just below $100^{\circ}C$.
Electric discharges were passed through the mixture to simulate lightning.
After a week, they observed the formation of simple organic compounds, primarily $Amino\,acids$ such as glycine, alanine, and aspartic acid.
Therefore, the correct answer is $Amino\,acids$.

(A) The theory of $Abiogenesis$ (also known as chemical evolution or spontaneous generation in a scientific context) proposes that life originated from non-living (abiotic) organic molecules through a series of gradual chemical reactions.
This concept is supported by the Oparin-Haldane hypothesis,which suggests that simple inorganic molecules combined to form complex organic compounds in the primitive atmosphere,eventually leading to the formation of the first primitive cell.
$Panspermia$ suggests life arrived from outer space,and $Biogenesis$ states that life arises only from pre-existing life.

(D) The $Theory$ $of$ $Special$ $Creation$ suggests that all living organisms that we see today were created in their current form. This theory has three connotations: $(1)$ All living organisms (species or types) that we see today were created as such. $(2)$ The diversity was always the same since creation and will remain the same in the future. $(3)$ The Earth is about $4000$ years old.

(C) According to conventional religious literature,the Earth is considered to be approximately $4000$ years old. This is a historical/mythological perspective mentioned in the context of evolutionary biology to contrast with scientific estimates of $4.5$ billion years.

(B) The history of the Earth is essentially the history of the universe. In the context of evolutionary biology,the history of the Earth is considered equivalent to the history of life on Earth,which is referred to as the biological history. This encompasses the origin of life,the diversification of species,and the evolutionary changes that have occurred over billions of years.

(D) According to the evolutionary timeline provided in the $NCERT$ biology textbook,invertebrates originated approximately $500$ million years ago (mya).
This period marks a significant diversification in the history of life on Earth,leading to the development of various invertebrate phyla.

(B) According to the theory of chemical evolution,life originated from non-living organic molecules.
$1$. First,simple organic molecules formed,which then polymerized to form macromolecules (like proteins,nucleic acids,etc.).
$2$. These macromolecules aggregated to form non-cellular aggregates (like coacervates or protobionts).
$3$. These aggregates eventually gave rise to the first primitive unicellular organisms.
$4$. Over millions of years,unicellular organisms evolved into complex multicellular organisms.
Therefore,the correct evolutionary sequence is: Macromolecules $\rightarrow$ Non-cellular aggregates $\rightarrow$ Unicellular organisms $\rightarrow$ Multicellular organisms.

(A) The origin of the universe is estimated to be $20$ billion years ago $(Y-1)$.
The Earth was formed approximately $4.5$ billion years ago $(X-2)$.
The first non-cellular forms of life originated about $3.0$ billion years ago $(Z-3)$.
Therefore, the correct matching is $X-2, Y-1, Z-3$.

(D) Stanley Miller,an American scientist,conducted a famous experiment in $1953$ to test the Oparin-Haldane hypothesis of chemical evolution.
He created an environment in a closed flask that simulated the conditions of the primitive Earth's atmosphere,using a mixture of $CH_4$,$H_2$,$NH_3$,and water vapor at $800^{\circ}C$.
He observed the formation of amino acids in his experiment.
Option $D$ is incorrect because Miller's experiment resulted in the formation of amino acids,not sugars,nitrogen bases,pigments,or fats.

(D) The provided diagram represents the Miller-Urey experiment,which simulated the conditions of the primitive Earth to study the origin of life.
In this apparatus:
$X$ represents the condenser,which cools the water vapor and gases to form liquid water (simulating rain).
$Y$ represents the electrodes,which provide an electric discharge (simulating lightning) to supply energy for chemical reactions between the gases $(CH_4, NH_3, H_2, H_2O)$.
Therefore,$X$ is the condenser and $Y$ is the electrodes.

(A) The provided figure represents the Miller-Urey experiment,which was designed to simulate the conditions of the early Earth to study the origin of life.
In this apparatus:
$1$. The label $b$ points to the main flask containing water,which is heated to produce water vapor,and it also collects the condensed water containing organic compounds (like amino acids) formed during the experiment.
$2$. The label $z$ represents the vacuum pump,which is used to evacuate the air from the apparatus to create a controlled environment (anaerobic conditions) before introducing the specific gases $(CH_4, NH_3, H_2)$.
Therefore,$b$ represents water containing organic compounds and $z$ represents the vacuum pump.

(B) The diagram represents the Miller-Urey experiment,which simulated the conditions of the primitive Earth's atmosphere.
In this experiment,a mixture of gases was used in the spark discharge chamber (labeled '$b$').
The gases used were methane $(CH_{4})$,ammonia $(NH_{3})$,water vapor $(H_{2}O)$,and hydrogen $(H_{2})$.
Therefore,'$b$' represents the mixture of these gases.

(B) The Big Bang theory is a cosmological model that explains the origin of the universe. It was first proposed by the Belgian astronomer and physicist Georges Lemaître in $1927$. He suggested that the universe began from a single point or 'primeval atom' and has been expanding ever since.

(B) In $1953$,Stanley Miller and Harold Urey conducted an experiment to simulate the conditions of the primitive Earth's atmosphere.
They used a closed flask containing a mixture of gases: methane $(CH_4)$,ammonia $(NH_3)$,and hydrogen $(H_2)$ in a ratio of $2 : 1 : 2$.
This mixture was subjected to electric discharges at $800^{\circ}C$ to simulate lightning.
The experiment successfully produced amino acids,providing evidence for the chemical evolution of life.

(A) In $1953$,Stanley Miller and Harold Urey conducted a landmark experiment to test the Oparin-Haldane hypothesis of chemical evolution.
They created an atmosphere in a closed flask containing $CH_4$,$H_2$,$NH_3$,and water vapor at a temperature of $800^{\circ}C$ using electric discharges.
This experiment resulted in the formation of amino acids,providing experimental evidence that life could have originated from non-living chemical substances.

(C) In $1953$, Stanley Miller and Harold Urey conducted an experiment to simulate the conditions of the primitive Earth's atmosphere. They used a mixture of $CH_4$, $NH_3$, $H_2$, and water vapor in a closed flask and provided energy through electric sparks. The analysis of the resulting mixture showed the formation of simple amino acids like $Glycine$, $Alanine$, and $Aspartic$ acid $(Aspartate)$. $Asparagine$ was not among the amino acids produced in this experiment.

(C) According to the Oparin-Haldane theory of the origin of life,life originated in the primitive oceans (water). The chemical evolution of life took place in the 'primordial soup' or 'hot dilute soup' present in the early oceans,where simple organic molecules formed complex organic compounds,eventually leading to the first primitive cells.

(D) The Earth was formed approximately $4.5$ billion years ago.
Life appeared on Earth about $500$ million years after the formation of the Earth.
This corresponds to approximately $4$ billion years ago.
Therefore,the correct option is $D$.

(B) Oparin of Russia and Haldane of England proposed the prebiotic soup theory.
The primordial soup is a term used to describe the aqueous solution of organic compounds that accumulated in primitive water bodies of the early Earth.
According to this theory,the first form of life could have emerged $3.8$ billion to $3.55$ billion years ago in a pond or ocean from pre-existing non-living organic molecules (such as $RNA$,proteins,etc.).
The formation of life was preceded by chemical evolution,which involved the formation of diverse organic molecules from inorganic constituents.

(C) $J. B. S. Haldane$ $(1920)$ used the term 'prebiotic soup' or 'hot dilute soup of organic substances' for oceanic water containing a mixture of simple organic compounds.
Methane $(CH_{4})$ was likely the first organic compound formed because the primitive atmosphere was reducing and lacked free oxygen.

(B) The universe is vast,relatively speaking,compared to the Earth,which is almost just a speck. The universe is very old,estimated to be approximately $20$ billion years old. The universe consists of huge clusters of galaxies.

(C) The primitive atmosphere of the Earth was reducing in nature,consisting primarily of methane $(CH_{4})$,ammonia $(NH_{3})$,hydrogen $(H_{2})$,and water vapor $(H_{2}O)$.
Free oxygen $(O_{2})$ was absent in the early atmosphere because it was highly reactive and would have oxidized the organic molecules necessary for the origin of life.

(B) Autotrophs are of two types:
$(i)$ Chemoautotrophs: The organisms performing chemosynthesis are called chemoautotrophs. They were anaerobic. Chemoautotrophs have the ability to synthesize organic molecules from inorganic raw materials. Such a mode of nutrition is present even now in some bacteria,$e.g.$,sulphur bacteria,iron bacteria,and nitrifying bacteria.
$(ii)$ Photoautotrophs: The photosynthetic organisms,the photoautotrophs,contain the pigment chlorophyll,which is formed by the combination of simple chemicals. They prepared organic food by using solar energy captured with the help of chlorophyll. They lacked the biochemical pathways to produce oxygen. They were anaerobic and utilized hydrogen from sources other than water.

(A) Microspheres are spherical structures formed by the aggregation of proteinoids. Sydney Fox $(1950)$ demonstrated that heating a dry mixture of amino acids to $130^{\circ}C-180^{\circ}C$ results in the formation of proteinoids or polypeptides. When these are cooled in water,they form protenoid microspheres with a diameter of $1-2 \mu m$. These microspheres possess a membrane composed of lipids and proteins,which mimics the structure of modern cell membranes and represents a primitive form of protobiont.

(B) During the process of chemical evolution,smaller and simpler organic compounds gradually combined to form complex organic compounds.
Amino acids polymerized to form polypeptides and proteins.
Similarly,nitrogenous bases (purines and pyrimidines) combined with sugars and phosphates to form nucleotides,which eventually polymerized to form nucleic acids ($RNA$ and $DNA$).
These complex molecules were essential for the origin of life.

(A) The first cellular form of life could have originated about $2000$ million years ago.
Experimental Evidences of Chemical Evolution:
In $1953$,$S$.$L$. Miller and $H$.$C$. Urey performed an experiment to test the chemical theory of evolution.
They created an electric discharge in a closed flask containing $CH_4$,$H_2$,$NH_3$,and water vapour at $800^{\circ}C$. They observed the formation of amino acids. In similar experiments,others observed the formation of sugars,nitrogen bases,pigments,and fats.
The first non-cellular forms of life could have originated $3$ billion years back. The first cellular form of life did not possibly originate until about $2000$ million years ago (or $2$ billion years ago) because the conditions were not suitable for biogenesis before that time. This version of biogenesis,i.e.,the first form of life arose slowly through evolutionary forces from non-living molecules,was accepted by the majority.

(B) The theory described is the Theory of Spontaneous Generation,also known as Abiogenesis or Autogenesis.
This theory states that life originated from non-living matter in a spontaneous manner.
This concept was supported by early Greek philosophers such as Thales,Anaximander,Xenophanes,Empedocles,Plato,and Aristotle.

(A) In $1953$,Stanley Miller and Harold Urey conducted a landmark experiment to test the Oparin-Haldane hypothesis of the chemical evolution of life.
They created a laboratory environment simulating the conditions of the primitive Earth,including high temperatures,volcanic storms,and a reducing atmosphere containing $CH_4$,$NH_3$,$H_2$,and water vapor.
After running the experiment for a week,they observed the formation of simple amino acids,which provided experimental evidence that life could have originated from non-living organic molecules.