CBSE Class 12 Biology Evolution Assignment Set 01

Question. Development of different functional structures from a common ancestral form is called
(a) differential evolution
(b) adaptive radiation
(c) non-adaptive radiation
(d) regressive evolution
Answer : B

Question. The process by which different type of finches were evolved in Galapagos islands is a consequence of
(a) adaptive radiation
(b) geographic similarity
(c) geographic dissimilarity
(d) adaptive convergence
Answer : A

Question. The diversity in the type of finches and adaptation to different feeding habits on the Galapagos islands, as observed by Darwin, provides an evidence of
(a) origin of species by natural selection
(b) intraspecific variation
(c) intraspecific competition
(d) interspecific competition
Answer : A

Question. What does presence of homologous organs in different animals indicate?
(a) Different ancestry
(b) Common ancestry
(c) Independent development
(d) Dependent development
Answer : B

Question. Which concept was not included in Charles Darwin’s theory of natural selection?
(a) Survival of the fittest
(b) Struggle for existence
(c) Overproduction of offspring
(d) Punctuated equilibrium
Answer : D

Question. What is the difference between natural selection and sexual selection?
(a) Sexual selection occurs during sexual intercourse
(b) Natural selection is a type of sexual selection
(c) Sexual selection is an example of natural selection
(d) Sexual selection occurs within demes
Answer : C

Question. Tendrils of Cucurbita and thorns of Bougainvillea are examples of
(a) vestigial organs
(b) analogous organs
(c) homologous organs
(d) homoplasy
Answer : C

Question. Which one of the following options gives one correct example each of convergent evolution and divergent evolution? 

Answer : A

Question. During which period did the first seed plant appear?
(a) Silurian
(b) Devonian
(c) Carboniferous
(d) Cretaceous
Answer : B

Question. The Cenozoic era is often designated as
(a) age of fish
(b) age of reptiles
(c) age of mammals
(d) age of amphibians
Answer : C

Question. In which era Protozoa, sponge and algae originate?
(a) Cenozoic era
(b) Azoic era
(c) Proterozoic era
(d) Mesozoic era
Answer : C

Question. What was the most significant trend in the evolution of modern man (Homo sapiens) from his ancestors?
(a) Shortening of jaws
(b) Binocular vision
(c) Increasing brain capacity
(d) Upright posture
Answer : C

Question. Who used hides to protect their body and buried their dead?
(a) Neanderthal man
(b) Homo habilis
(c) Australopithecus
(d) Dryopithecus
Answer : A

Question. The correct order of evolutionary scale is
(a) Palaeozoic → Archaeozoic → Cenozoic
(b) Archaeozoic → Palaeozoic → Proterozoic
(c) Palaeozoic → Mesozoic → Cenozoic
(d) Mesozoic → Archaeozoic → Proterozoic
Answer : C

Question. First dinosaurs and first egg-laying mammals originated in
(a) Jurassic period
(b) Triassic period
(c) Permian period
(d) Cambrian period
Answer : B

Question. Identify the geographical periods (A, B, C) in the given diagram.

(a) A–Tertiary, B–Jurassic, C–Permian
(b) A–Tertiary, B–Permian, C–Jurassic
(c) A–Permian, B–Jurassic, C–Tertiary
(d) A–Jurassic, B–Tertiary, C–Permian
Answer : C

Question. Choose the incorrectly matched pair.
(a) Reptiles — Thick-shelled eggs which do not dry up
(b) Tyrannosaurus rex — Fish like reptile
(c) Dinosaurs — May be evolved into birds
(d) Continental drift — South America joined North-America
Answer : B

Question. The first viviparous mammals whose fossils are small-sized were like
(a) shrews
(b) monkeys
(c) rats
(d) lobefins
Answer : A

Question. In which epoch, only modern humans prevail?
(a) Pleiostocene
(b) Holocene
(c) Pliocene
(d) Miocene
Answer : B

Question. Which phenomena confined the pouched mammals to Australia they survived because of lack of competition from any other mammals?
(a) Continental origination
(b) Continental shifting
(c) Continental drift
(d) Continental evolution
Answer : C

Question. Choose the incorrect pair.
(a) Ramapithecus – Man-like
(b) Dryopithecus – Ape-like
(c) Fossil of man-like bones were discovered – Ethopia and Tanzania
(d) Australopithecus – Probably lived in Western Africa desert
Answer : B

Question. First human like hominid is known as
(a) Neanderthal man
(b) Homo habilis
(c) Dryopithecus
(d) Homo erectus
Answer : B

Question. Brain (cranial) capacity of Homo habilis was
(a) 750-850 cc
(b) 750-800 cc
(c) 650-800 cc
(d) 550-700 cc
Answer : C

Question. The fossil finding suggest that closest fossil to Homo habilis was
(a) Homo erectus
(b) Homo sapiens
(c) Dryopithecus
(d) Neanderthal man
Answer : A

Question. Which of the following is an extinct animal?
(a) Protopterus
(b) Equus
(c) Archaeopteryx
(d) Columba
Answer : C

Question. Mesozoic era is called the age of
(a) fishes
(b) amphibians
(c) reptiles
(d) birds
Answer : C

Question. The most recent era in geological time scale is
(a) Mesozoic
(b) Cenozoic
(c) Palaeozoic
(d) Proterozoic
Answer : B

Question. The extinct human who lived 10,00,00 to 40,000 years ago, in Europe, Asia and parts of Africa, with short stature, heavy eyebrows, retreating fore heads,large jaws with heavy teeth, stocky bodies, a lumbering gait and stooped posture was
(a) Homo habilis 
(b) Neanderthal human
(c) Cro-Magnon human
(d) Ramapithecus
Answer : B

Question. Homo sapiens, neanderthalensis and Cro-Magnon man, probably originated from
(a) Homo erectus
(b) Homo habilis
(c) Ramapithecus
(d) Proconsul
Answer : A

Question. The difference between Homo sapiens and Homo erectus was
(a) Homo sapiens originated in Africa, while Homo erectus originated in Asia
(b) Homo erectus were much smaller in size than Homo sapiens
(c) Homo erectus stayed in Africa, while Homo sapiens did not
(d) the size of the brain of Homo erectus was smaller than that of Homo sapiens
Answer : D

Question. Who was more intelligent than modern man,cave-dweller, had prominent chin and appeared after neanderthal man?
(a) Erect man
(b) Cro-Magnon man
(c) Hominid tool maker
(d) First ape man
Answer : B

Question. Homo sapiens most likely arose in
(a) India
(b) America
(c) England
(d) Africa
Answer : D

Question. Homo sapiens arose during
(a) ice age between 75000-10000 years ago
(b) continental drift between 75000-10000 years ago
(c) continental drift between 75000-5000 years ago
(d) ice age between 50000-10000 years ago
Answer : A

Question. Stellar distance is measured in :
(a) Kilometer
(b) Light years
(c) Per socond
(d) None

Answer :  B

Question. When more than one adaptive radiation appeared to have occurred in an isolated geographical area, it is called as :
(a) Divergent evolution
(b) Convergent evolution
(c) Parallel evolution
(d) Continental drift

Answer :  B

Question. Out of the following which is an example of convergent evolution ?
(A) Eyes of octopus and mammals
(B) Flippers of penguins and Dolphins
(C) Sweet potato and potato
(a) A and C
(b) A and B
(c) B and C
(d) A, B and C

 Answer :  D

Question. What was the food habit of the original variety of Darwin's finches from which many other varieties were developed ?2
(a) Seed eater
(b) Cactus eater
(c) Wood pecker
(d) Fruit eater

 Answer :  A

Question. What were two main key points of Darwinian theory of natural selection ?
(a) Branching descent
(b) Natural selection
(c) Fitness
(d) Both 1 and 2

Answer :  D

Question. During evolution the first cellular form of life appeared before how many million years ?
(a) 2000
(b) 400
(c) 100
(d) 50

Answer :  A

Question. The biggest dinosour, which appeared during evolution was :
(a) Thecodont
(b) Stegosaurus
(c) Triceratops
(d) Tyrannosaurus rex

Answer :  D

Ques. What was the most significant trend in the evolution of modern man (Homo sapiens) from his ancestors?
(a) Shortening of jaws
(b) Binocular vision
(c) Increasing cranial capacity
(d) Upright posture 

Answer: C

Ques. The extinct human who lived 1,00,000 to 40,000 years ago, in Europe, Asia and parts of Africa, with short stature, heavy eye brows, retreating fore heads, large jaws with heavy teeth, stocky bodies, a lumbering gait and stooped posture was
(a) Homo habilis
(b) Neanderthal human
(c) Cro-magnon human
(d) Ramapithecus. 

Answer: B

Ques. The most apparent change during the evolutionary history of Homo sapiens is traced in
(a) loss of body hair
(b) walking upright
(c) shortening of the jaws
(d) remarkable increase in the brain size

Answer: D

Ques. There are two opposing views about origin of modern man. According to one view Homo erectus in Asia were the ancestors of modern man. A study of variation of DNA however suggested African origin of modern man. What kind of observation on DNA variation could suggest this?
(a) Greater variation in Asia than in Africa
(b) Greater variation in Africa than in Asia
(c) Similar variation in Africa and Asia
(d) Variation only in Asia and no variation in Africa

Answer: B

Ques. What kind of evidence suggested that man is more closely related with chimpanzee than with other hominoid apes?
(a) Evidence from DNA extracted from sex chromosomes only
(b) Comparison of chromosomes morphology only
(c) Evidence from fossil remains, and the fossil mitochondrial DNA alone
(d) Evidence from DNA extracted from sex chromosomes, autosomes. 

Answer: D

Ques. In recent years, DNA sequences (nucleotide sequence) of mtDNA and Y chromosomes were considered for the study of human evolution, because
(a) they are small and therefore, easy to study
(b) they are uniparental in origin and do not take part in recombination
(c) their structure is known in greater detail
(d) they can be studied from the samples of fossil remains. 

Answer: B

Ques. According to fossils discovered up to present time origin and evolution of man started from
(a) France
(b) Java
(c) Africa
(d) China. 

Answer: C

Ques. Which of the following is closest relative of man?
(a) Chimpanzee
(b) Gorilla
(c) Orangutan
(d) Gibbon 

Answer: A

Ques. Which of the following is correct order of the evolutionary history of man?
(a) Peking man, Homo sapiens, Neanderthal man, Cromagnon man
(b) Peking man, Heidelberg man, Neanderthal man, Cromagnon man
(c) Peking man, Neanderthal man, Homo sapiens, Cromagnon man
(d) Peking man, Neanderthal man, Homo sapiens, Heidelberg man 

Answer: B

Ques. Homo sapiens have evolved in
(a) Paleocene
(b) Pleistocene
(c) Oligocene
(d) Holocene. 

Answer: D

Ques. Character which is closely related to human evolution is
(a) disappearance of tail
(b) reduction in size of jaws
(c) binocular vision
(d) flat nails. 

Answer: A

Ques. Who is directly related to man?
(a) Gorilla
(b) Rhesus
(c) Gibbon
(d) Orangutan 

Answer: A

Ques. Which one of the following statements is correct?
(a) Australopithecus is the real ancestor of modern man.
(b) Neanderthal man is the direct ancestor of Homo sapiens.
(c) Homo erectus is the ancestor of man.
(d) Cro-magnon man’s fossil has been found in Ethiopia. 

Answer: C

Ques. The age of the fossil of Dryopithecus on the geological time scale is
(a) 2.5 × 106 years back
(b) 50 × 106 years back
(c) 75 × 106 years back
(d) 25 × 106 years back. 

Answer: A

Ques. Which of the following statements is correct regarding evolution of mankind?
(a) Homo erectus is preceded by Homo habilis.
(b) Neanderthal man and cro-magnon man were living at the same time.
(c) Australopithecus was living in Australia.
(d) None of these 

Answer: A

Ques. Common origin of man and chimpanzee is best shown by
(a) binocular vision
(b) chromosome number
(c) dental formula
(d) cranial capacity.

Answer: D

Ques. Which of the following changes for man in the course of evolution is probably useless?
(a) Development of being erect
(b) Development of cranial capacity
(c) Loss of tail
(d) Development of opposable thumb 

Answer: C

Ques. Which of the following is the direct ancestor of Homo sapiens?
(a) Australopithecus
(b) H. sapiens neanderthals
(c) Homo erectus
(d) Homo sapiens fossilis 

Answer: D

Ques. The first domesticated animal by primitive man was
(a) cat
(b) cow
(c) dog
(d) horse. 

Answer: C

Ques. Which one of the following changes involved is irrelevant, in the evolution of man?
(a) Perfection of hand for tool making
(b) Change of diet from hard nuts and hard roots to soft food
(c) Loss of tail
(d) Increase in the ability to communicate with others and develop community behaviour

Answer: B

Question. During natural selection which variety of Bistonbetularia was completely wiped out from England?
(a) White winged moth
(b) Dark winged moth
(c) Both of them
(d) None of them

Answer : D

Question. In which type of natural selection the peak gets higher and narrower ?
(a) Stabilising selection
(b) Directional selection
(c) Disruptive selection
(d) None of these

Answer : A

Question. Fore limbs of whale, bat, cheetah and human are example of :
(a) Analogous organs
(b) Homologous organs
(c) Homoplastic organs
(d) Vestigial organs

Answer : B

Question. Tasmanian Wolf, Tiger Cat, Sugar glider are example of :
(a) Convergent evolution
(b) Adaptive radiation
(c) Australian marsupials
(d) 2 and 3 both

Answer : D

Question. Which of the following statements is true ?
(a) During evolution, the rate of appearance of new form of organisms is linked to the life cycle/life span.
(b) The essence of Darwinian theory is natural selection.
(c) Fitness is based on characteristics which are inherited.
(d) All of them

Answer : D

Question. Hugo de vries called the single step large mutation as :
(a) Mutation
(b) Sports
(c) Micro evolution
(d) Saltation

 Answer : D

Question. The industrial melanism phenomenon demonstrate:
(a) Gene mutation
(b) Genetic drift
(c) Natural selection
(d) Migration

Answer : C

Question. Which was absent in Miller's experiment ?
(a) Vacuum pump
(b) Electrodes
(c) Condenser
(d) None

Answer : D

Question. During human evolution the body of which primitive ancestors covered by hairs and walk they walked gorilla and chimpanzee?
(a) Dryopithecus and Cromagnon man
(b) Dryopithecus and Ramapithecus
(c) Ramapithecus and Homo habilis
(d) Java man and Peking man

Answer : B

Very Short Answer Type Questions

Question. What is the most important pre-condition for adaptive radiation?
Answer : Conditions promoting adaptive radiation are much of the diversity of life originated through episodes of adaptive radiation during periods when ecological space became available for diversification. There are two primary mechanisms through which ecological space can become available. (i) intrinsic changes in organisms. (ii) extrinsic effects, including environmental change and colonisation of isolated landmasses.

Question. How do we compute the age of a rock?
Answer : The age of a rock in years is called its absolute age. It is determined by the natural radioactive decay of certain elements, e.g., uranium, when decays turns into lead. The parent atoms of uranium are converted into daughter atoms of lead over a fixed interval of time. This interval is the decay constant. The ratio of parent-daughter atoms changes in a quantity that can be measured. The radioactive half-life (the amount of time required for one half of the parent atoms to beonverted to daughter atoms) is used to calculate the age of the rock.

Question. When we talk of functional macromolecules (e.g., proteins as enzymes, hormones, receptors, antibodies etc), towards what are they evolving?
Answer : Functional macromolecules are evolving towards creation of a complex organism. There are various evidences that are common to simple and complex forms of lite indicate common ancestry, e.g., histones protein tend to be well preserved among all eukaryotes, from amoebas to blue whale or to humans, with only one or two amino acids different. The genetic code is nearly identical for all known life forms, from bacteria to archaea or animals and plants.

Question. In a certain population, the frequency of three genotypes is as follows Genotypes BB Bb bb Frequency 22% 62% 16% What is the likely frequency of B and b alleles?
Answer : The likely frequency of B = BB + 1 2 Bb 

Question. Among the five factors that are known to affect Hardy-Weinberg equilibrium, three factors are gene flow, genetic drift and genetic recombination. What are the other two factors?
Answer : The other two factors that affect Hardy-Weinberg equilibrium are mutation and natural selection. Mutation is a sudden heritable change in an organism which is generally due to change in the base sequence of the nucleic acid in the organism’s genome. Microbial experiments show that pre-existing advantageous mutations when selected will result in formation of new phenotypes. Over few generations, this would result in speciation. Thus, resulting in changed frequency of genes and alleles. Natural selection is a phenomenon by which organisms possessing heritable variations enabling their better survival reproduce and leave greater number of progeny than their counterpart. It can lead to stabilisation (in which more individuals acquire mean character value), directional change (more individuals acquire value other than the mean character value) or disruption (more individuals acquire peripheral character value at both ends of the distribution curve).

Question. What is founder effect?
Answer : Sometimes, a small number of individuals become isolated from a larger population to form a new population at some distance away from their place of origin. The gene pool of the new population differs from the source population. It is possible that the change in allele frequency is so drastically different in the new sample that they become a different species. The original driftted population becomes founders and this effect is called founder effect.

Question. Who among the Dryopithecus and Ramapithecus was more man like?
Answer : Ramapithecus was more man-like. It walked erect on its hind legs, ate hard nuts and seeds like modern man and had jaws and teeth similar to humans It arose from Dryopithecus, which was considered to be a common ancestor of man and apes. Dryopithecus was more ape-like with same length of arms and legs.

Question. By what Latin name, the first Hominid was known?
Answer : The first hominid was known as Homo habilis. The brain capacities were between 650-800cc. They probably did not eat meat.

Question. Among Ramapithecus, Australopithecines and Homo habilis who probably did not eat meat?
Answer : Homo habilis probably did not eat meat. This creature was the first human like being, with brain capacities between 650-800cc.

 Short Answer Type Questions

Question. State and explain any three factors affecting allele frequency in populations.
Answer : Factors affecting allele frequency in populations are as described below (i) Mutations These are sudden heritable changes which are supposed to be the primary source of genetic variation. They are of following two types (a) Chromosomal Mutations They arise due to changes in chromosome number and changes in structure. (b) Gene Mutations These are changes in gene structure and expression due to addition, deletion, substitution or inversion of nucleotides. (ii) Non-random Mating Repeated mating between individuals of certain selected traits changes the gene frequency, e.g., selection of more brightly coloured male bird by a female bird may increase the gene frequency of bright colour in the next generation. (iii) Gene Flow (Gene Migration) It is the movement of alleles into and out of a gene pool. Breeding of immigrants with the host population adds new alleles to the gene pool of the host population.

Question. Gene flow occurs through generations. Gene flow can occur across language barriers in humans If we have a technique of measuring specific allele frequencies in different population of the world, can we not predict human migratory patterns in pre-history and history? Do you agree or disagree? Provide explanation to your answer.
Answer : Yes, we agree. As the gene flow occurs through geographical barriers over generations, by studying specific allelic frequencies in various populations of the world, we can predict the human migratory patterns in pre-historic and historic era. There have been projects undertaken such as human genographics project. Which uses data from studies on specific genes/chromosomes/mitochondrial DNA to trace the evolutionary history and migratory patterns of humans

Question. How do you express the meaning of worlds like race, breed, cultivars or variety?
Answer : The meaning of the given words are as given below Race It is a classification system used to categorise humans into large and distinct populations or groups by anatomical, cultural, linguistic, geographical, historical and for relegious relationship. Breed It is a specific group of domestic animals or plants having homogenous appearance, homogenous behaviour and other characteristics that distinguish it from other animals or plants of the same species and that were arrived at through selective breeding. Cultivar It is a plant or grouping of plants selected for desirable characteristics that can be maintained by propogation. ‘Cultivar’ stands for ‘cultivated variety’. Variety A variety arises naturally in the plant kingdom and plant grown from its seeds will typically come out true to type.

Question. When we say ‘survival of the fittest’, does it mean that (a) those which are fit only survive (b) those that survive are called fit? Comment.
Answer : In the struggle for existence, the individuals which have more favourable variations will enjoy a competitive advantage over others which have less favourable or unfavourable variations. They are considered fit and thus, will survive and reproduce. Such individuals produce more progeny (with more fit individuals) than others who are less adapted in that environment.

Question. Enumerate three most characteristic criteria for designating a Mendelian population.
Answer : Characteristic criteria for designating a Mendelian population are
(i) Population must be sufficiently large.
(ii) Population must have potentialities for free flow of genetic material among individuals, through sexual reproduction.
(iii) Migration should either be nil or negligible.

Question. ‘Migration may enhance or blurr the effects of selection’ comment.
Answer : The movement of individuals from one place to another is called migration. It can be the movement of individuals to a different populations (i.e., emigration) or movement of individual into a particular population (i.e., cmmigration) Migration may bring in more such alleles, that bestow upon the individuals, such adaptations or traits which are selected by nature. Thus, enhancing the effect of selection. Similarly, emigration may lead to removal of such alleles that confer better adaptations. Immigration may also bring in those alleles which confer the traits that are not selected by nature, i.e., blurr the effects of selection. Hence, it is justifiable to say that ‘Migration may enhance or blurr the effects of selection.

VSA (1 MARK)

Question 1. Name one fish like reptile that evolved from land reptile about 200 million years ago?
Answer: Ichthyosaurs.
In simple words: Ichthyosaurs are aquatic reptiles that evolved from land ancestors around 200 million years ago and looked similar to fish.

Exam Tip: Memorize key evolutionary timelines and specific organism names as they frequently appear in 1-mark questions.

Question 2. For a long time, it was believed that life originated from decaying matter. What is this theory known as? Name the scientist who experimentally disproved this theory.
Answer: This theory is known as the Theory of Spontaneous Generation. Louis Pasteur experimentally disproved this theory.
In simple words: People once thought life could spring from rotting mud or straw, but Louis Pasteur proved living things only come from pre-existing life using sterilized flask experiments.

Exam Tip: Link Louis Pasteur directly with the disproof of spontaneous generation and his swan-neck flask experiment.

Question 3. If abiotic origin of life is in progress on a planet other than earth, what should be the conditions there?
Answer: The conditions required would be very high temperature, volcanic storms, and a reducing atmosphere containing gases such as \(\text{CH}_4\), \(\text{NH}_3\), \(\text{H}_2\), and water vapors, but lacking free oxygen.
In simple words: To create life from non-living chemicals, a planet needs extreme heat, volcanic activity, and an atmosphere full of methane, ammonia, and hydrogen without any oxygen.

Exam Tip: Mention the absence of free oxygen and the presence of specific reducing gases for full credit.

Question 4. Name the person who proposed that population tends to increase geometrically while food production increases arithmetically.
Answer: Thomas Malthus.
In simple words: Thomas Malthus observed that human population grows much faster than the food supply available to sustain it.

Exam Tip: Malthus's essay on population heavily influenced Charles Darwin's theory of natural selection.

Question 5. Name the scientist who had also come to similar conclusion as that of Darwin about natural selection as a mechanism of evolution. Which place did he visit to come to conclusions?
Answer: Alfred Wallace. He visited the Malay Archipelago.
In simple words: Alfred Wallace independently arrived at the same conclusions on natural selection as Darwin after studying wildlife in the Malay Archipelago.

Exam Tip: Always associate Alfred Wallace with the Malay Archipelago and his joint paper presentation with Darwin.

SA-II (2 MARKS)

Question 6. Explain Oparin-Haldane theory of chemical evolution of life.
Answer: According to the Oparin-Haldane theory, the first form of life could have originated from pre-existing non-living organic molecules (such as RNA, proteins, etc.). This abiogenic origin of life was preceded by chemical evolution, where inorganic compounds combined under primitive Earth conditions (high temperature, volcanic activity, reducing atmosphere) to form diverse organic compounds.
In simple words: Life started when simple non-living chemicals reacted in the harsh environment of early Earth to form complex organic building blocks over time.

Exam Tip: Emphasize that chemical evolution preceded biological evolution.

Question 7. Distinguish between convergent and divergent evolution giving one example of each.
Answer:
1. Divergent Evolution: It shows the relationship of structures having the same basic structural origin and embryonic development but performing different functions in different species (homology). Example: Forelimbs of mammals (whale, bat, cheetah, human).
2. Convergent Evolution: It shows the relationship of structures having functional similarities and similar outward appearance but different structural origin and embryonic development (analogy). Example: Wings of insects and wings of birds.
In simple words: Divergent evolution means same structure adapted for different uses (homology), while convergent evolution means different structures adapted for the same use (analogy).

Question 8. What is adaptive radiation? Explain with an example.
Answer: The process of evolution of different species in a given geographical area starting from a point and radiating to other habitats is called adaptive radiation. Example: Darwin's finches found on the Galapagos Islands, where a single seed-eating ancestral species migrated to different islands and radiated into multiple species with diverse beak structures adapted for different diets.
In simple words: Adaptive radiation is when one ancestral species branches out into many new species to fill different ecological niches in a new habitat.

Exam Tip: Mention both the point of origin and the radiation into different habitats along with Darwin's finches as the classic example.

Question 9. How did Louis Pasteur disprove spontaneous generation theory?
Answer: Louis Pasteur demonstrated by using pre-sterilized swan-neck flasks that in flasks where air was sterilized or filtered, life did not arise from killed yeast because dust and microbes were trapped in the curved neck. However, in another flask whose neck was broken and exposed directly to air, new organisms rapidly arose from the air-borne spores acting on the killed yeast.
In simple words: Pasteur showed that sterilized broth stays sterile as long as dust and germs from the air are kept out, proving life only comes from pre-existing life.

Exam Tip: Describe the swan-neck flask setup clearly, highlighting the role of air exposure and dust trapping.

SA-I (3 MARKS)

Question 10. (i) State the Hardy-Weinberg principle.
(ii) When there is a disturbance in the Hardy-Weinberg equilibrium, what would it result in?
(iii) According to this principle, what is the sum total of all allelic frequencies?
Answer:
(i) The Hardy-Weinberg principle states that allele frequencies in a population are stable and constant from generation to generation under gene pool equilibrium.
(ii) Any disturbance or change in Hardy-Weinberg equilibrium results in evolution or speciation.
(iii) The sum total of all allelic frequencies in a population is always equal to 1 (\(p + q = 1\)).
In simple words: Gene frequencies remain constant unless disrupted by evolutionary forces, and all allele frequencies together always add up to 1.

Exam Tip: Remember the mathematical expression \(p^2 + 2pq + q^2 = 1\) and that sum of allele frequencies equals 1.

Question 11. Classify the following as examples of homology and analogy-
(i) Hearts of fish and crocodile
(ii) Wings of butterfly and birds
(iii) Eyes of Octopus and Mammals
(iv) Tubers of potato and Sweet potato
(v) Thorns of Bougainvillea and spines of Opuntia
(vi) Thorn of Bougainvillea and tendrils of cucurbits.
Answer:
(i) Hearts of fish and crocodile: Homology
(ii) Wings of butterfly and birds: Analogy
(iii) Eyes of Octopus and Mammals: Analogy
(iv) Tubers of potato and Sweet potato: Analogy
(v) Thorns of Bougainvillea and spines of Opuntia: Analogy
(vi) Thorn of Bougainvillea and tendrils of cucurbits: Homology
In simple words: Organs with the same embryonic origin are homologous, while organs with different origins performing similar functions are analogous.

Exam Tip: Potato tuber is a modified stem while sweet potato root is a modified root (analogy); Bougainvillea thorn and cucurbit tendril are both modified stems (homology).

Question 12. Stanley Miller and Harold Urey performed an experiment by recreating in the laboratory the probable conditions of the atmosphere of the primitive earth.
(i) What was the aim of the experiment?
(ii) In what forms was the energy supplied for chemical reactions to occur?
(iii) For how long was the experiment run continuously? Name two products formed.
Answer:
(i) The aim was to prove Oparin-Haldane's theory of chemical origin of life.
(ii) Energy was supplied in the form of electric discharge using electrodes (simulating lightning) along with high temperature.
(iii) The experiment was run continuously for one week (7 days). Two key products formed were amino acids and simple sugars.
In simple words: Miller and Urey recreated early Earth conditions with electric sparks for a week and proved that organic molecules like amino acids form naturally.

Exam Tip: Note the exact gas mixture (\(\text{CH}_4, \text{NH}_3, \text{H}_2, \text{H}_2\text{O}\)), temperature, and duration (one week) for complete answers.

Question 13. 'Industrial Melanism' in peppered moth is an excellent example of 'Natural selection'. Justify the statement.
Answer: Before industrialization in England, tree trunks were covered with light-colored lichens, making white-winged moths camouflaged and dark-winged moths easily spotted and eaten by birds. After industrialization, soot covered the trees, killing lichens and darkening trunks; consequently, white-winged moths became easy prey while dark-winged (melanized) moths survived and reproduced. This directional shift driven by environmental change demonstrates evolution through natural selection.
In simple words: Industrial soot changed tree colors, allowing dark moths to hide better from predators and survive while light moths were eaten, proving natural selection in action.

Exam Tip: Use the terms camouflaged, predators, industrial soot, and differential survival to score full credit.

Question 14. Fill up the blanks left in the table showing Era, period and organism.

Answer: (a) Quaternary, (b) Cenozoic, (c) Cretaceous, (d) Mesozoic, (e) Carboniferous, (f) Paleozoic.
In simple words: The geological table is filled by matching the correct eras, periods, and evolutionary milestones.

Exam Tip: Memorize the major geological eras (Paleozoic, Mesozoic, Cenozoic) and their corresponding periods.

Question 15. (i) In which part of the world, Neanderthal man lived?
(ii) What was his brain's capacity?
(iii) Mention the advancement which Neanderthal man showed over Homo erectus.
Answer:
(i) Neanderthal man lived in near Eastern and Central Asia.
(ii) His brain capacity was about 1400 c.c.
(iii) They showed greater brain capacity, used animal hides to protect and cover their bodies, and buried their dead.
In simple words: Neanderthals lived in Central/Near Asia, had a large 1400 cc brain, wore clothes, and buried their dead.

Exam Tip: 1400 c.c. brain capacity and burial of the dead are hallmark traits of Neanderthals.

Question 16. Figures given below are of Darwin's finches? Variety of beaks of Darwin's finches.
(a) Mention the specific geographical area where these were found.
(b) Name and explain the phenomenon that has resulted in the evolution of such diverse species in the region.
(c) How did Darwin visit the particular geographical area?
Answer:
(a) Galapagos Islands.
(b) Adaptive radiation. It is the process of evolution of different species in a given geographical area starting from a point and radiating to other habitats, adapting to different food habits (e.g., seed-eating, insect-eating beaks).
(c) Darwin visited the Galapagos Islands through a sea voyage in a sail ship called H.M.S. Beagle.
In simple words: Darwin studied finches in the Galapagos Islands that evolved different beaks from a common ancestor through adaptive radiation after arriving on the H.M.S. Beagle.

Exam Tip: Link H.M.S. Beagle, Galapagos Islands, and adaptive radiation together for complete marks.

Question 17. Give examples to show evolution by anthropogenic action.
Answer: Excess use of herbicides, pesticides, and synthetic chemicals has resulted in the selection of resistant varieties of weeds and insects in a much lesser time scale. Similarly, the excessive use of antibiotics and drugs has resulted in the selection of drug-resistant microbes and bacteria.
In simple words: Human activities like using pesticides and antibiotics have rapidly forced pests and bacteria to evolve resistance.

Exam Tip: Anthropogenic action means evolution driven or influenced by human activities.

LA (5 MARKS)

Question 18. Is evolution a 'process' or the end result of a 'process'? Discuss. Describe various factors that effect Hardy-Weinberg equilibrium.
Answer: Evolution is considered both a process and the consequence of a process. It is a slow, continuous historical process driven by natural selection acting on genetic variation, and simultaneously the end result of changes in gene frequencies over generations. Factors affecting Hardy-Weinberg equilibrium include:
1. Gene Migration or Gene Flow: Movement of alleles between populations.
2. Genetic Drift: Random change in allele frequencies by chance.
3. Mutations: Sudden heritable changes in genetic material.
4. Genetic Recombination: New combinations of alleles during sexual reproduction.
5. Natural Selection: Differential survival and reproduction of better-adapted individuals.
In simple words: Evolution is an ongoing biological process resulting from genetic changes, influenced by migration, drift, mutation, recombination, and natural selection.

Question 19. How do Darwin and Hugo de Vries after regarding Mechanism of Evolution?
Answer:
- Charles Darwin: Believed that evolution is gradual, slow, and directional, driven by small, continuous variations and natural selection.
- Hugo de Vries: Put forth the mutation theory, stating that evolution is driven by mutations which are sudden, random, and directional, causing speciation in a single step (saltation).
In simple words: Darwin thought evolution happens through slow, small, gradual changes, whereas Hugo de Vries believed it happens through sudden, random large mutations.

Question 20. With the help of suitable diagram, represent the operation of natural selection on different traits.
Answer: Natural selection can affect the distribution of traits in a population in three ways: directional selection (shifts the peak towards one extreme), stabilizing selection (favors intermediate phenotypes, narrowing the curve), and disruptive selection (favors both extremes, creating two peaks).
In simple words: Natural selection can narrow down traits to an average, split them into two extremes, or push the population in one new direction.

Exam Tip: Label the three types of natural selection (stabilizing, directional, disruptive) clearly in diagrams and descriptions.