Correct Answer: (b)
The Big Bang theory describes the origin and early evolution of the entire universe, not just Earth or life. It proposes that the universe began as an incredibly hot and dense point and has been expanding ever since. This theory is supported by observations such as the redshift of distant galaxies and the cosmic microwave background.
Q2. Assertion: Resistance of microbes to antibiotics is an example of anthropogenic evolution.
Reason: It is a result of excessive use of antibiotics by human actions.
Correct Answer: (a)
Antibiotic resistance in bacteria has evolved largely due to human overuse and misuse of antibiotics, which exerts strong selection pressure. The reason correctly identifies the human‑induced cause, making it the explanation for the assertion. Thus, both are true and the reason is the correct explanation.
Q3. Match the historical timeline:
A. Cave Art
18,000 years back
B. Agriculture
10,000 years back
C. Homo sapiens arose
75,000-10,000 years back
Correct Answer: (a)
Cave paintings date to about 18,000 years ago; agriculture began around 10,000 years ago; and modern Homo sapiens appeared within the last 75,000–10,000 years. All the matches are accurate.
Q4. Which of the following is correct for 'Homo sapiens'? (i) Arose in Africa. (ii) Developed into distinct races. (iii) Arose during the ice age (75,000-10,000 years ago).
Correct Answer: (a)
Homo sapiens originated in Africa and later spread across the globe, giving rise to various races. Their emergence is placed within the last 75,000–10,000 years, a period that includes the last ice age. All statements are supported by current anthropological evidence.
Q5. The study of history of life forms on earth is called:
Correct Answer: (b)
Evolutionary Biology is the branch that deals with the history of life forms on Earth. It traces how organisms have changed over millions of years through various processes. This field integrates evidence from fossils, comparative anatomy, and molecular biology to reconstruct the evolutionary relationships among species.
Q6. Which of the following phylum/group characteristics is being described? (i) They are viviparous and protect unborn young. (ii) They are more intelligent in sensing danger. (iii) They took over the earth when reptiles came down.
Correct Answer: (c)
Mammals are viviparous (most give birth to live young) and care for their offspring. They have larger brains relative to body size, allowing complex behaviours and intelligence. After the demise of dinosaurs (reptiles), mammals diversified and became the dominant terrestrial vertebrates. Thus, the description fits mammals.
Q7. Assertion: Pre-historic cave art developed about 18,000 years ago.
Reason: Agriculture came around 10,000 years back.
Correct Answer: (a)
Cave paintings date to roughly 18,000 years ago, and agriculture emerged about 10,000 years ago. Both are chronological milestones, but the appearance of agriculture does not explain why cave art developed earlier. Hence, both are true but the reason is not the correct explanation.
Q8. Assertion: When we see stars, we are apparently looking into the past.
Reason: Stellar distances are measured in light years and take millions of years to reach our eyes.
Correct Answer: (a)
The assertion is true because light from stars takes a finite time to travel to Earth. The reason correctly explains this: since distances are measured in light years, the light we see today left the star many years ago. Therefore, we are indeed looking at the star as it was in the past, and the reason directly supports the assertion.
Q9. Which are correct for 'Panspermia'? (i) units of life called spores were transferred to earth. (ii) Idea from early Greek thinkers. (iii) Still a favourite idea for some astronomers.
Correct Answer: (a)
Panspermia is the hypothesis that life, or its precursors, arrived on Earth from outer space via spores or comets. The idea has ancient Greek origins and is still considered by some scientists as a possible explanation for the origin of life. All statements are correct.
Q10. Which of the following is correct regarding 'Adaptive Radiation' in Australia? (i) Marsupials evolved from an ancestral stock within the island. (ii) They show convergent evolution with placental mammals. (iii) Tasmanian wolf is a marsupial corresponding to placental wolf.
Correct Answer: (a)
Australian marsupials diversified from a common ancestor, exhibiting adaptive radiation. Many marsupials have evolved similarities to placental mammals due to convergent evolution (e.g., the Tasmanian wolf resembles a placental wolf). All three statements are correct.
Q11. Match the Following ancestors:
A. Dryopithecus
More ape-like
B. Ramapithecus
More man-like
C. Australopithecines
East African grasslands
Correct Answer: (a)
Dryopithecus was an ape‑like ancestor, Ramapithecus was man‑like, and Australopithecines lived in East African grasslands. All three statements are correct, so the matching is all correct.
Q12. The process of 'Industrial Melanism' in England is an example of:
Correct Answer: (b)
Industrial melanism describes how dark‑coloured moths became more common in polluted areas due to natural selection. Before the industrial revolution, light moths were camouflaged against lichen‑covered trees. As pollution darkened the trees, dark (melanic) moths became better hidden from predators, increasing their survival and reproduction.
Q13. Identify true statements for 'Paleontological Evidence': (i) Fossils are remains of hard parts of life-forms. (ii) Fossils in different sedimentary layers indicate the geological period. (iii) study showed life-forms varied over time.
Correct Answer: (a)
Fossils preserve hard parts such as bones, shells, and teeth. They occur in sedimentary rock layers, and the sequence of fossils reveals changes in life forms over geological time. All three statements are accurate.
Q14. Assertion: Genetic drift operates in large populations.
Reason: Migration of a section of population causes gene flow.
Correct Answer: (a)
Genetic drift is a random change in allele frequencies that has a stronger effect in small populations. The assertion that it operates in large populations is false. The reason, however, is true: migration is a cause of gene flow. Thus, assertion false, reason true.
Q15. Identify the correct statements for human evolution: (i) Homo habilis did not eat meat. (ii) Homo erectus had a large brain (900cc). (iii) Neanderthal man buried their dead.
Correct Answer: (c)
Homo habilis likely consumed meat, as evidenced by tool marks on animal bones, so statement (i) is false. Homo erectus had a brain size of about 900cc (true). Neanderthals are known to have buried their dead (true). Therefore, only statements (ii) and (iii) are correct.
Q16. Assertion: Evolution is a stochastic process.
Reason: It is based on chance events in nature and chance mutation in organisms.
Correct Answer: (a)
Evolution involves random mutations, genetic drift, and other stochastic (chance) events, though natural selection acts in a non‑random way. The reason correctly states that chance events play a role in evolution, thereby explaining why the process is stochastic. Both the assertion and reason are true, and the reason supports the assertion.
Q17. The sum total of all allelic frequencies in a population according to Hardy-Weinberg is:
Correct Answer: (c)
The Hardy‑Weinberg principle states that the sum of all allele frequencies for a given gene in a population equals 1 (or 100%). If there are two alleles, p and q, then p + q = 1. This equation forms the basis for calculating genotype frequencies and detecting evolutionary changes.
Q18. Placental wolf and Tasmanian wolf-marsupial are examples of:
Correct Answer: (b)
Convergent evolution is the independent evolution of similar features in distantly related species that occupy similar environments. The placental wolf and the marsupial Tasmanian wolf are not closely related but have evolved similar body shapes and predatory habits. This similarity arises from comparable selective pressures, not common ancestry.
Q19. Assertion: The first mammals were like shrews.
Reason: Their fossils are small sized.
Correct Answer: (a)
Early mammals were indeed small, shrew‑like creatures that coexisted with dinosaurs. The reason (small fossil size) is a true observation but does not explain why they were like shrews; shrew‑like refers to a combination of traits, not just size. Therefore, both statements are true, but the reason is not the correct explanation.
Q20. Assertion: Homology is based on divergent evolution.
Reason: The same structure developed along different directions due to adaptations to different needs.
Correct Answer: (a)
Homologous structures share a common origin but have evolved to serve different functions, a process called divergent evolution. The reason accurately describes how the same basic anatomical plan can be modified by natural selection for varied environments. Thus, the reason logically explains why homology arises from divergent evolution.
Q21. Identify the correct statements for 'Analogy': (i) Result of convergent evolution. (ii) Different structures evolving for same function. (iii) Example is sweet potato and potato.
Correct Answer: (a)
Analogy arises from convergent evolution, where unrelated organisms evolve similar structures for similar functions. Sweet potato (root) and potato (stem) are both storage organs but derived from different tissues, serving the same purpose. Thus, all statements are correct.
Q22. Match the organs with their type:
Organ Pair
Type
A. Thorn of Bougainvillea / Tendril of Cucurbita
(I) Homologous
B. Wings of butterfly and birds
(II) Analogous
C. Flippers of Penguins and Dolphins
(III) Analogous
D. Eye of Octopus and Mammals
(IV) Analogous
Correct Answer: (a)
Thorn of Bougainvillea and tendril of Cucurbita are both modified branches, so they are homologous (I). Wings of butterfly and birds are analogous (II). Flippers of penguins (birds) and dolphins (mammals) are analogous (III). The eye of octopus and mammals are analogous (IV). All pairings A–I, B–II, C–III, D–IV are correct.
Q23. Assertion: Hardy-Weinberg equilibrium is affected by gene flow.
Reason: New genes are added to the new population and lost from the old.
Correct Answer: (a)
Gene flow (migration) changes allele frequencies by introducing new alleles into a population and removing them from another. The reason correctly describes the mechanism of gene flow, thereby explaining how it disrupts Hardy‑Weinberg equilibrium. Both are true and the reason is the correct explanation.
Q24. The two key concepts of Darwinian Theory of Evolution are:
Correct Answer: (b)
Darwin’s theory rests on two pillars: branching descent (common ancestry) and natural selection. Branching descent means that all organisms are related through a tree of life, and natural selection is the mechanism that drives adaptive change. Together, they explain the diversity and unity of life.
Q25. Select true statements for 'Divergent Evolution': (i) Same structure developed along different directions. (ii) due to adaptations to different needs. (iii) Indicates common ancestry.
Correct Answer: (a)
Divergent evolution occurs when a common ancestral structure is modified to perform different functions in different environments. This process results in homologous organs and indicates shared ancestry. All three statements are correct.
Q26. The first cellular forms of life did not possibly originate till about ______ million years ago.
Correct Answer: (c)
The earliest cellular organisms (prokaryotes) are estimated to have appeared around 2,000 million years ago (2 billion years). This is based on fossil evidence of stromatolites and microfossils from that period. Cellular life required the development of membranes, genetic material, and metabolic machinery, which took time to evolve from non‑cellular precursors.
Q27. Fitness, according to Darwin, refers ultimately and only to:
Correct Answer: (c)
In Darwinian terms, fitness is measured by an organism’s ability to survive and produce viable offspring that can also reproduce. It is not about physical prowess or size but about leaving more copies of one’s genes in the next generation. An individual with higher reproductive fitness passes on its advantageous traits more effectively.
Q28. Regarding 'Human Genome Project' (HGP) facts mentioned in Unit VII intro: (i) It sequenced the whole human genome. (ii) Involved major contributions from Watson and Crick.
Correct Answer: (a)
The Human Genome Project successfully sequenced the entire human genome. Watson and Crick are famous for discovering the double‑helix structure of DNA, but they did not directly contribute to the HGP. Therefore, only statement (i) is correct.
Q29. Match the natural selection patterns (Figure 6.8):
Pattern
Effect
A. Stabilising
(I) Peak shifts in one direction
B. Directional
(II) Two peaks form
C. Disruptive
(III) Peak gets higher and narrower
Correct Answer: (a)
Stabilising selection narrows the distribution around the mean, making the peak higher and narrower (III). Directional selection shifts the peak in one direction (I). Disruptive selection creates two peaks (II). Hence, A–III, B–I, C–II.
Q30. Life appeared ______ million years after the formation of earth.
Correct Answer: (b)
Fossil evidence and geochemical traces suggest that life emerged relatively soon after Earth's formation. The oldest known fossils are about 3.5 billion years old, but isotopic signatures hint at life as early as 3.8–4.0 billion years ago. Thus, life appeared roughly 500 million years after the Earth itself formed.
Q31. Assertion: Dinosaurs suddenly disappeared about 65 mya.
Reason: We do not know the true reason for their disappearance.
Correct Answer: (b)
It is accepted that dinosaurs went extinct at the K‑Pg boundary about 65 million years ago. While the exact cause is still debated (asteroid impact, volcanism, etc.), the reason that we don't know the true reason is a separate fact. It does not explain the assertion; it simply states a limitation in our knowledge. Thus, both true but reason not the explanation.
Q32. When an original drifted population becomes the source of a new population, it is called:
Correct Answer: (c)
The founder effect occurs when a small group of individuals breaks off from a larger population and establishes a new colony. The gene pool of the new population is derived from this small sample, which may have different allele frequencies than the original population. This can lead to rapid genetic divergence and speciation.
Q33. Who reached similar conclusions as Darwin while working in the Malay Archipelago?
Correct Answer: (b)
Alfred Russel Wallace independently conceived the theory of evolution by natural selection while studying the biogeography of the Malay Archipelago. He sent a manuscript to Darwin, which prompted Darwin to publish his own work. Both naturalists recognised that species change over time and that competition and variation drive evolutionary change.
Q34. Match the following for fossil types:
Organism
Time of dominance/Event
A. Invertebrates
(I) 350 mya
B. Jawless fish
(II) 500 mya
C. Dinosaurs disappeared
(III) 65 mya
D. Fish like reptiles (Ichthyosaurs)
(IV) 200 mya
Correct Answer: (a)
Invertebrates dominated around 500 mya (II). Jawless fish appeared about 350 mya (I). Dinosaurs went extinct at 65 mya (III). Ichthyosaurs (fish‑like reptiles) lived around 200 mya (IV). So the matching is A–II, B–I, C–III, D–IV.
Q35. Assertion: The embryo of all vertebrates develop a row of vestigial gill slits.
Reason: Gill slits are functional organs in all adult vertebrates.
Correct Answer: (a)
Vertebrate embryos, including humans, have pharyngeal pouches that resemble gill slits, but they are non‑functional and usually disappear before birth. The reason is false because gill slits are only functional in adult fish and some amphibians; in other vertebrates, they are vestigial or modified into other structures. Hence, assertion true, reason false.
Q36. In the Miller-Urey experiment, the temperature maintained was:
Correct Answer: (b)
Stanley Miller and Harold Urey simulated early Earth conditions by heating a mixture of water vapour, methane, ammonia, and hydrogen to 800°C. They passed electric sparks through the gases to mimic lightning. The resulting mixture cooled and condensed, and they later found amino acids, the building blocks of proteins, showing that simple organic compounds can form abiotically.
Q37. Assertion: Australopithecines essentially ate fruit.
Reason: Evidence shows they hunted with stone weapons.
Correct Answer: (c)
Australopithecines were primarily frugivorous (fruit‑eaters) based on dental and isotopic evidence. The reason is false because stone‑tool hunting is associated with later hominins like Homo habilis or Homo erectus, not with australopithecines. Thus, assertion true, reason false.
Q38. Which are correct regarding 'Lamarckism'? (i) Driven by use and disuse of organs. (ii) Acquired characters are passed to next generation. (iii) Example of long-necked giraffes.
Correct Answer: (a)
Lamarck proposed that organs become stronger or weaker through use/disuse, and these acquired traits are inherited. He used the giraffe’s long neck as a classic example. All three statements correctly describe Lamarckism.
Q39. Assertion: T. rex was about 20 feet in height.
Reason: It had fearsome dagger-like teeth.
Correct Answer: (b)
Tyrannosaurus rex is estimated to have been about 20 feet tall, and it indeed had large, serrated teeth. However, the size of its teeth does not explain its overall height; height is a result of skeletal structure, not dentition. Therefore, both statements are true, but the reason does not explain the assertion.
Q40. Identify the correct statements regarding Darwin's Finches: (i) They were observed in Galapagos Islands. (ii) They diversified into insectivorous and vegetarian forms. (iii) They represent an example of adaptive radiation.
Correct Answer: (a)
All three statements are correct. Darwin observed finches in the Galapagos. They evolved different beak shapes for insect‑eating, seed‑eating, and other diets. This diversification from a single ancestor into multiple niches is a textbook example of adaptive radiation.
Q41. Who proposed the 'theory of use and disuse' of organs using the example of Giraffes?
Correct Answer: (c)
Jean‑Baptiste Lamarck put forward the idea that organisms develop traits through the use or disuse of organs, and these acquired characteristics can be inherited. He famously used the giraffe’s long neck as an example: ancestors stretched their necks to reach leaves, leading to longer necks in offspring. This theory is now largely rejected in favour of Darwinian natural selection.
Q42. Assertion: Wings of butterfly and birds are analogous structures.
Reason: They are anatomically similar but perform different functions.
Correct Answer: (a)
The assertion is correct: wings of butterflies and birds are analogous because they are not derived from a common ancestral wing but have evolved independently for flight. However, the reason is false because they are not anatomically similar—they differ in structure (butterfly wings are chitinous, bird wings are feathered). They perform the same function (flight), not different ones. Hence, assertion true, reason false.
Q43. Earth was supposed to have been formed about ______ billion years ago.
Correct Answer: (c)
Geological and radiometric dating of meteorites and Earth's oldest rocks indicate that our planet formed around 4.5 billion years ago. This estimate aligns with the age of the solar system, which condensed from a solar nebula. The early Earth was molten and gradually cooled, eventually leading to the formation of continents and oceans.
Q44. Assertion: Neanderthal man lived in near east and central Asia.
Reason: They had a brain size of 1400cc.
Correct Answer: (a)
Neanderthals inhabited the Near East and Central Asia, and their brain capacity was indeed around 1400cc. However, brain size does not explain their geographic distribution. Both statements are true, but the reason is not the explanation for the assertion.
Q45. Organs that are similar in anatomical structure but perform different functions are:
Correct Answer: (b)
Homologous organs share a common embryonic origin and basic structural plan but have adapted to different functions. For example, the forelimbs of humans, whales, and bats are built from the same bones but serve different purposes. This similarity indicates divergent evolution from a common ancestor.
Q46. Match the evolutionary concepts in Column-I with descriptions in Column-II:
Column-I
Column-II
A. Homology
(I) Convergent evolution
B. Analogy
(II) Divergent evolution
C. Adaptive Radiation
(III) Darwin's Finches
D. Saltation
(IV) de Vries
Correct Answer: (a)
Homology is based on divergent evolution (II). Analogy arises from convergent evolution (I). Adaptive radiation is exemplified by Darwin's finches (III). Saltation is a term coined by de Vries (IV). Thus, the correct matching is A–II, B–I, C–III, D–IV.
Q47. Assertion: Ramapithecus was more ape-like.
Reason: Dryopithecus was more man-like.
Correct Answer: (a)
These statements are factually reversed: Ramapithecus was more man‑like (with hominid features) and Dryopithecus was more ape‑like. Hence, both the assertion and the reason are false. This is a common error to avoid.
Q48. Select the correct statements for 'Hardy-Weinberg equilibrium': (i) Allele frequencies are stable in a population. (ii) Gene pool remains constant. (iii) It is affected by five factors including genetic drift and gene flow.
Correct Answer: (a)
Hardy‑Weinberg equilibrium describes a population where allele frequencies do not change across generations. This requires a constant gene pool, and the equilibrium can be disrupted by factors such as mutation, genetic drift, gene flow, natural selection, and non‑random mating. All three statements are correct.
Q49. Assertion: Homo erectus probably ate meat.
Reason: Fossils of Homo erectus were discovered in Java in 1891.
Correct Answer: (a)
The assertion is true; Homo erectus is believed to have consumed meat based on tool marks on bones and dietary evidence. The reason is also true but refers to a historical discovery, not evidence for diet. Therefore, both are true but the reason does not explain the assertion.
Q50. Which of the following are correct for 'Homologous Organs'? (i) They share a common ancestry. (ii) They represent divergent evolution. (iii) Example includes forelimbs of whales and cheetahs.
Correct Answer: (a)
Homologous organs are derived from a common ancestor, exhibit divergent evolution, and are exemplified by the forelimbs of whales (flippers) and cheetahs (legs), which have similar bone structure but different functions. All statements are correct.
Q51. Assertion: Spontaneous generation theory was dismissed by Louis Pasteur.
Reason: He showed that in pre-sterilised flasks, life did not come from killed yeast.
Correct Answer: (a)
Pasteur’s experiments were pivotal in refuting spontaneous generation. He used swan‑neck flasks to show that no life appeared in sterilised broth unless dust and microbes from the air were allowed in. The reason accurately describes his methodology and proves that life arises only from pre‑existing life, thereby providing a sound explanation for the assertion.
Q52. The first non-cellular forms of life could have originated ______ billion years back.
Correct Answer: (b)
Non‑cellular life forms, such as self‑replicating RNA molecules or protobionts, are thought to have appeared about 3 billion years ago. These entities preceded true cells and may have been the first step toward cellular life. They could have formed through chemical evolution in the primordial soup.
Q53. Assertion: The first organisms that invaded land were plants.
Reason: Plants were widespread on land when animals invaded land.
Correct Answer: (a)
Plants were indeed the first to colonise land, creating soil and oxygenating the atmosphere, which paved the way for animals. The reason correctly points out that plants established the terrestrial ecosystem before animals, so animals could later invade. Hence, the reason is the correct explanation.
Q54. Hugo de Vries called 'single step large mutation' as:
Correct Answer: (c)
Hugo de Vries coined the term ‘saltation’ to describe a sudden, large mutation that could give rise to a new species in a single generation. He believed that such drastic changes were the primary source of evolutionary novelty, in contrast to Darwin’s idea of gradual variation. This concept influenced early mutation theory.
Q55. Match the Hardy-Weinberg terms for a diploid:
Term
Frequency
A. AA
(I) 2pq
B. aa
(II) p^2
C. Aa
(III) q^2
Correct Answer: (a)
In Hardy‑Weinberg equilibrium, the genotype frequencies are: AA = p² (II), aa = q² (III), and Aa = 2pq (I). Therefore, the correct matching is A–II, B–III, C–I.
Q56. Stellar distances are measured in:
Correct Answer: (c)
Light year is the distance that light travels in one year, which is about 9.46 trillion kilometres. Since stars are extremely far away, using kilometres would yield unwieldy numbers. Light years provide a convenient and practical unit for expressing astronomical distances.
Q57. Assertion: Darwin's finches represent one of the best examples of adaptive radiation.
Reason: They evolved from a single ancestral stock within the Galapagos Island.
Correct Answer: (a)
The assertion is true: Darwin’s finches are a classic case of adaptive radiation. The reason is also true and directly explains why—they all descended from a common ancestor on the islands and diversified into various ecological niches. Therefore, the reason provides the correct explanation for the assertion.
Q58. Assertion: Natural selection can lead to stabilization.
Reason: In stabilization, more individuals acquire mean character value.
Correct Answer: (a)
Stabilising selection favours the average phenotype and reduces variation around the mean. The reason correctly describes that in stabilising selection, individuals with intermediate traits are more common. Therefore, the reason accurately explains how natural selection can lead to stabilisation.
Q59. Darwin made his observations during a sea voyage on a ship called:
Correct Answer: (a)
Charles Darwin served as a naturalist on the H.M.S. Beagle during its five‑year voyage around the world (1831‑1836). His observations of diverse flora and fauna, especially in the Galapagos Islands, laid the foundation for his theory of evolution by natural selection. The voyage provided him with crucial biogeographical and geological evidence.
Q60. The evolution of different species in a given geographical area starting from a point is:
Correct Answer: (b)
Adaptive radiation occurs when a single ancestral species diversifies into many new forms, each adapted to different ecological niches within the same region. The classic example is Darwin's finches on the Galapagos, where one finch species gave rise to multiple species with different beak shapes and feeding habits.
Q61. The brain capacity of Homo habilis was:
Correct Answer: (b)
Homo habilis, one of the earliest members of the genus Homo, had an average brain size between 650 and 800 cubic centimetres. This was larger than the australopithecines but smaller than later hominins like Homo erectus. The increased brain size is associated with more complex tool use and possibly early language abilities.
Q62. Match the following regarding Miller’s experiment:
A. CH4, H2, NH3, Water vapour
Input gases
B. Electric discharge
Energy source
C. Amino acids
Resulting molecules
Correct Answer: (a)
Miller used CH₄, H₂, NH₃, and water vapour as the input gases. He supplied energy via electric discharge (sparks). The products included amino acids. All three match correctly.
Q63. Match the human ancestors with their brain capacities:
Ancestor
Brain Capacity
A. Homo habilis
(I) 1400cc
B. Homo erectus
(II) 650-800cc
C. Neanderthal man
(III) 900cc
Correct Answer: (a)
Homo habilis had brain size 650‑800cc (II). Homo erectus had about 900cc (III). Neanderthal man had about 1400cc (I). Therefore, A–II, B–III, C–I.
Q64. Match the following for early earth history:
Event
Timeline
A. Formation of Earth
(I) 4 billion years back
B. Appearance of life
(II) 4.5 billion years back
C. First non-cellular life
(III) 2000 million years ago
D. First cellular life
(IV) 3 billion years back
Correct Answer: (a)
Earth formed 4.5 billion years ago (II). Life appeared about 4 billion years ago (I). Non‑cellular life originated around 3 billion years ago (IV). Cellular life appeared about 2 billion years ago (III). So the sequence is A–II, B–I, C–IV, D–III.
Q65. Which statements regarding 'Industrial Melanism' are true? (i) White moths were more abundant before industrialisation. (ii) Melanic moths survived better on dark trunks after industrialisation. (iii) No variant was completely wiped out.
Correct Answer: (a)
Before industrial pollution, light‑coloured moths were common on lichen‑covered trees. After pollution darkened the trees, dark (melanic) moths became camouflaged and increased in number. However, both variants persisted, and neither went extinct. All statements are true.
Q66. Assertion: Lichens can be used as industrial pollution indicators.
Reason: They will not grow in areas that are polluted with smoke and soots.
Correct Answer: (a)
Lichens are sensitive to air pollutants like sulfur dioxide and heavy metals, so their absence indicates pollution. The reason states that lichens do not grow in smoke‑ and soot‑polluted areas, which is a correct observation. Because this sensitivity is the basis for using them as indicators, the reason correctly explains the assertion.
Q67. Which of the following is correct? (i) Evolutionary Biology is the history of life forms. (ii) The universe is 13.8 billion years old. (iii) Earth is 4.5 billion years old.
Correct Answer: (a)
Evolutionary biology indeed studies the history of life. The universe’s age is estimated at 13.8 billion years, and Earth’s age is about 4.5 billion years. All three statements are correct.
Q68. The universe is almost ______ billion years old.
Correct Answer: (c)
The age of the universe is estimated from cosmic microwave background radiation and the expansion rate. The widely accepted value is about 13.8 billion years, which is supported by data from satellites like Planck. This timescale allows for the formation of galaxies, stars, and eventually our solar system.
Q69. Assertion: de Vries believed that mutations caused speciation.
Reason: Variations for de Vries were small and directional.
Correct Answer: (a)
De Vries proposed that mutations (which he called saltations) could produce new species in a single step. The reason is false because he considered mutations to be random and large, not small and directional. Small and directional variations were associated with Darwinian evolution. Hence, assertion true but reason false.
Q70. Regarding 'Mutations' as per de Vries: (i) They are random and directionless. (ii) They are the cause of evolution. (iii) They represent 'saltation'.
Correct Answer: (a)
De Vries considered mutations to be random, non‑directional changes that could produce new species in a single step (saltation). He believed that mutations are the raw material for evolution, and that large mutations could cause speciation. All three statements are correct.
Q71. Identify correct features of 'Founder Effect': (i) change in allele frequency is so different. (ii) Original drifted population becomes founders. (iii) leads to speciation.
Correct Answer: (a)
The founder effect results in a small group colonising a new area, carrying a non‑representative sample of the original gene pool. This can lead to significant genetic drift and potentially speciation. All three statements are correct.
Q72. Identify correct facts for 'Early Earth atmosphere': (i) No atmosphere initially. (ii) Contained water vapour, methane, and ammonia. (iii) UV rays broke up water into H2 and O2.
Correct Answer: (a)
Early Earth had no free oxygen; its atmosphere formed later from volcanic gases including water vapour, methane, ammonia, and CO₂. Ultraviolet radiation from the Sun split water vapour into hydrogen and oxygen, which eventually contributed to the development of an ozone layer. All statements are correct.
Q73. Who demonstrated that life comes only from pre-existing life using pre-sterilised flasks?
Correct Answer: (c)
Louis Pasteur’s famous experiment with swan‑neck flasks proved that microbes do not spontaneously generate in sterile broth. He boiled nutrient broth in flasks with curved necks that allowed air but prevented dust and microorganisms from entering. No growth occurred unless the flask was tilted to let the dust in, thereby establishing the principle of biogenesis.
Q74. Regarding the 'Hatch and Slack Pathway' (as used in Unit 4, but let's stick to Evolution PDF content): (i) The origin of life was preceded by chemical evolution. (ii) Oparin and Haldane proposed life came from non-living organic molecules. (iii) Miller provided the experimental proof.
Correct Answer: (a)
Chemical evolution (formation of organic molecules from inorganic ones) set the stage for life. Oparin and Haldane proposed that life originated from non‑living organic matter, and Miller’s experiment demonstrated that amino acids can be synthesized under simulated early Earth conditions. All three statements are accurate.
Q75. The theory that life came out of decaying and rotting matter like straw and mud is:
Correct Answer: (c)
Spontaneous generation was an ancient belief that life could arise from non‑living matter under certain conditions, such as rotting meat or mud. This idea was disproved by experiments like those of Francesco Redi and Louis Pasteur, who showed that life only comes from pre‑existing life.
Q76. Assertion: Australian marsupials evolved from an ancestral stock within the Australian island.
Reason: They represent an example of adaptive radiation.
Correct Answer: (a)
The marsupials of Australia diversified into many forms (wolves, kangaroos, moles) from a common ancestor, which is a classic example of adaptive radiation. The reason correctly identifies this phenomenon and explains how the diversification occurred. Hence, both are true and the reason is the correct explanation.
Q77. Agriculture and human settlements started approximately how many years back?
Correct Answer: (b)
The Neolithic Revolution, when humans began farming and domesticating animals, occurred about 10,000 years ago. This transition allowed for permanent settlements, larger populations, and the development of civilizations. It marks a major shift from a nomadic hunter‑gatherer lifestyle to a sedentary agricultural one.
Q78. Assertion: Phenylketonuria is caused by mutation in a single gene.
Reason: It is characterized by mental retardation and reduction in hair.
Correct Answer: (a)
PKU is indeed a single‑gene disorder caused by mutations in the PAH gene. The symptoms include mental retardation and light hair colour, but these are effects, not the cause. Therefore, both statements are true, but the reason does not explain the genetic cause; it merely describes the condition.
Q79. Regarding the 'Z-scheme' (from Unit 4 intro, referenced in Evolution PDF): (i) First organisms that invaded land were plants. (ii) Some early cells had the ability to release O2.
Correct Answer: (a)
Plants were the first to colonise land, creating an oxygen‑rich atmosphere. Early photosynthetic cells (like cyanobacteria) produced oxygen as a by‑product. Both statements are correct.
Q80. Assertion: The ozone layer was formed on early earth.
Reason: Oxygen combined with ammonia and methane to form water and CO2.
Correct Answer: (c)
The assertion is true: ozone (O₃) formed later after photosynthetic organisms released oxygen, which then reacted with UV light. The reason, however, is false because ozone formation does not involve oxygen combining with ammonia or methane; those reactions would consume oxygen, not produce ozone. Therefore, assertion true but reason false.