Multiple Choice Questions (MCQs): Evolution - NEET MCQ

Stanley Miller conducted a famous experiment in 1953 to provide experimental proof that hydrogen, methane, water, and ammonia can give rise to amino acids, the building blocks of proteins. The experiment was based on the hypothesis proposed by Russian scientist Alexander Oparin. Miller identified several amino acids, including glycine, alanine, and aspartic acid, in the mixture. The experiment demonstrated that simple organic molecules, such as amino acids, can be formed under conditions similar to those believed to exist on early Earth.

Topic in NCERT: Origin of life and chemical evolution

Line in NCERT: " in 1953, s.l. miller, an american scientist created similar conditions in a laboratory scale. he created electric discharge in a closed flask containing ch4, h2, nh3 and water vapour at 800°c. he observed formation of amino acids."

• Louis Pasteur in his swan neck flask experiment, found out that life originated from pre-existing life.
• He prepared sterilized syrup of sugar and later killed yeast by boiling them in flasks.

Topic in NCERT: Origin of life

Line in NCERT: "louis pasteur by careful experimentation demonstrated that life comes only from pre-existing life."

The primitive atmosphere of earth was reducing atmosphere with little or no oxygen but was rich in water vapour, carbon monoxide, carbon dioxide, nitrogen and hydrogen. Thus, oxygen was not present in primitive atmosphere. The high temperature, UV light and lightening provided energy for chemical reactions between hydrogen and free oxygen, nitrogen and carbon to form, ammonia, methane and cyanides. Owing to the high temperature of earth, water was present in form of superheated steam and ammonia, methane and cyanides were present in gaseous form. 

Therefore, the correct answer is option C.

Topic in NCERT: Origin of life

Line in NCERT: "oxygen combined with ammonia and methane to form water, co2 and others."

• It was at 800°C in which the flask was maintained along with electric discharge.
• A moderately high temperature was required to keep the flask sterilized.
• Thus, creating amino acids as the product.

Topic in NCERT: Evolution of life forms - a theory

Line in NCERT: "he created electric discharge in a closed flask containing ch4, h2, nh3 and water vapour at 800°c."

Origin of earth dates back around 4.6 billion years ago which makes options A and B incorrect as life originated only after the origin of earth. The period of 4.6 billion year ago to 3.8 billion years ago is termed as the Azoic era when the primitive earth conditions were too harsh to sustain any life form. During this period, the earth's temperature cooled down and the ocean and atmosphere were formed. The Archaeozoic era is marked by the appearance of first life form in the hot soup of the primitive ocean which dates back around 4 billion years ago. The first life forms were prokaryotic chemoheterotrophic anaerobic organisms.

Topic in NCERT: Origin of life

Line in NCERT: "life appeared 500 million years after the formation of earth, i.e., almost four billion years back."

Answer:
In his experiment, Stanley Miller synthesized the following:
- Virus: Not synthesized by Stanley Miller in his experiment.
- Protein: Not synthesized by Stanley Miller in his experiment.
- Amino acid: Stanley Miller successfully synthesized amino acids in his experiment. Amino acids are the building blocks of proteins and are essential for life.
- Cell: Stanley Miller did not synthesize cells in his experiment.
Therefore, the correct answer is option C: Amino acid. Stanley Miller's experiment demonstrated that the conditions present in the early Earth's atmosphere can lead to the formation of amino acids, which is an important step in the origin of life on Earth.

Topic in NCERT: Origin of life

Line in NCERT: "he observed formation of amino acids."

• Water is most important for the origin of life because it acts as a universal solvent, enabling chemical reactions that are essential for life processes.
• It provides the medium for biochemical reactions, regulates temperature, and participates directly in chemical reactions.
• These unique properties make water indispensable for the formation and sustenance of life.

Topic in NCERT: Origin of life

Line in NCERT: "all life forms were in water environment only."

Theory of spontaneous generation believed that life originated spontaneously from the non-living decaying and rotting matter like straw and mud. This theory was disproved by Louis Pasteur. Louis Pasteur demonstrated that life comes from the pre-existing life.
Correct option is B. 

Topic in NCERT: Origin of life

Line in NCERT: For a long time it was also believed that life came out of decaying and rotting matter like straw, mud, etc. This was the theory of spontaneous generation.

• Charles Darwin had set voyage around the world in a ship named H.M.S Beagle.
• He traveled to different islands to research about evolution.
• He found out that the existing living organisms had many similarities with life forms that existed millions of years ago.

Topic in NCERT: Evolution of life forms - a theory

Line in NCERT: "based on observations made during a sea voyage in a sail ship called h.m.s. beagle round the world, charles darwin concluded that existing living forms share similarities to varying degrees not only among themselves but also with life forms that existed millions of years ago."

• Evolution is a stochastic process, which means that it is focusing on chance mutations.
• Based on determinism, evolution is not a direct process.
• It is also based on events that occurs in a chance.

Topic in NCERT: Mechanism of evolution

Line in NCERT: "it is a stochastic process based on chance events in nature and chance mutation in the organisms."

• Two mya, Australopithecines probably lived in East African grasslands.
• Fossils discovered in Java in 1891 revealed the next stage, i.e., Homo erectus about 1.5 mya.
• The Neanderthal man with a brain size of 1400cc lived in near east and central Asia between 1,00,000 - 40,000 years back.
• During ice age between 75,000 - 10,000 years ago modern Homo sapiens arose.

Topic in NCERT: Origin and evolution of man

Line in NCERT: "a rough sketch of the evolution of life forms, their times on a geological scale are indicated in (figures 6.9 and 6.10). homo erectus probably ate meat. the neanderthal man with a brain size of 1400cc lived in near east and central asia between 1,00,000-40,000 years back. homo sapiens arose in africa and moved across continents and developed into distinct races."

Bacteria is first inhabited in earth and so bacteria is heterotroph option C is correct.

Topic in NCERT: Evolution of life forms - a theory

Line in NCERT: "the first cellular form of life did not possibly originate till about 2000 million years ago. these were probably single-cells."

Evolution for Darwin was gradual while deVries believed mutation caused speciation and hence called it saltation (single step large mutation).

Topic in NCERT: Mechanism of evolution

Line in NCERT: "hugo devries based on his work on evening primrose brought forth the idea of mutations - large difference arising suddenly in a population. he believed that it is mutation which causes evolution and not the minor variations (heritable) that darwin talked about. [...] devries believed mutation caused speciation and hence called it saltation (single step large mutation)."