Maharashtra Board Class 10 Science Chapter 1 Heredity and Evolution Solutions

 

Question 1. Complete the following diagram.
ℹ️ चित्र व्याख्या (Diagram Explanation): यह आरेख 'विकास के साक्ष्य' को दर्शाता है। यह एक केंद्रीय बॉक्स 'एविडेंसेस ऑफ एवोल्यूशन' से चार मुख्य शाखाओं में विभाजित होता है: मॉर्फोलॉजिकल (आकृति विज्ञान), पलायंटोलॉजिकल (जीवाश्म विज्ञान), हड्डियों की संरचना में समानताएं (एनाटॉमिकल), और एम्ब्रायोलॉजिकल (भ्रूण विज्ञान)। यह पूर्ण आरेख जीव विकास के विभिन्न प्रमाणों को वर्गीकृत करता है।

🎯 Exam Tip: Diagram completion questions require accurate recall of categories and their placement. Focus on clearly identifying each type of evidence for evolution to score maximum marks.

 

Question 2. Read the following statements and justify same in your own words with the help of suituble examples.
a. Human evolution began approximately 7 crore years ago.
Answer:
• Approximately around 7 crore years back the ice age began on the earth. In such conditions, dinosaurs became extinct. The evolution and diversity of mammals started during this time. Due to change in climate the forest cover also declined rapidly.
• Ancestors of monkey-like animals were Lemur-like animals which evolved during this time period.
• The tails of these monkey-like creatures started vanishing very gradually around 4 crore years ago.
• The body and brain both increased in volume forming first ape-like animals. The monkey-like ancestors gave rise to two evolutionary links to apes and human-like animals.
• Later, the human evolution took place by changes in the brain volume, the ability to walk upright, excessive use of hand for manipulations.
• This journey of human evolution began 7 crore years ago. But the true wise and intelligent man arose around 50,000 years ago.
In simple words: Human evolution started about 7 crore years ago, beginning with Lemur-like ancestors and progressing through ape-like forms, increased brain volume, upright walking, and enhanced hand use, leading to modern humans about 50,000 years ago.

🎯 Exam Tip: When justifying historical statements, always provide a chronological sequence of events and mention key evolutionary milestones and their approximate timings for clarity and accuracy.

 

b. Geographical and reproductive isolation of organisms gradually leads to speciation.
Answer:
• Every species survives in specific geographical conditions. The requirements of food and habitat, is specific for each species. Their reproductive ability and period is also different.
• Therefore, the individuals from one species cannot reproduce with individuals from other species.
• When they are separated by a distance or geographical barriers they are said to be isolated geographically.
• When they cannot reproduce with each other, they are said to be isolated reproductively.
• The ancestor species of both these subspecies may be the same but due to isolation over a very long-time duration, there is genetic variation between the two. Therefore, the isolation leads to speciation.
In simple words: When populations of a species become geographically separated, they can no longer interbreed, leading to reproductive isolation. Over long periods, genetic variations accumulate in these isolated groups, eventually resulting in the formation of distinct new species.

🎯 Exam Tip: Clearly differentiate between geographical and reproductive isolation, and emphasize how genetic variation accumulates over time to drive speciation.

 

c. Study of fossils is an important aspect of study of evolution.
Answer:
• Fossils offer palaeontological evidence for the evolutionary process.
• Due to some natural calamities the organisms get buried during ancient times.
• The impressions and remnants of such organisms remain preserved underground. The hot lava also traps some organisms or their impressions. All such formations form fossils.
• Study of fossils help the researcher to understand the characteristics of the organisms that existed in the past.
• Carbon dating method also helps in finding out exact age of the fossil. According to the structure of earth's crust the fossils are obtained at specific depths.
• The oldest ones are obtained at the depth while the relatively recent ones occupy the upper surface. Thus fossils of invertebrates were seen in very old Palaeozoic era. Later were seen fossils of Pisces, Amphibia and Reptilia. The Mesozoic era was dominated by reptiles while Coenozoic era showed presence of mammals.
• In this way, study of fossils unfold the evolutionary secrets.
In simple words: Fossils provide direct evidence of past life forms and their changes over time, acting as a historical record of evolution. Techniques like carbon dating help determine the age of these fossils, revealing the sequence of life on Earth and demonstrating how different species evolved.

🎯 Exam Tip: Mention the different types of information fossils provide (characteristics of past organisms, age, and geological distribution) and the role of carbon dating to secure full marks.

 

d. Among different chordates there are embryological evidences.
Answer:
• Very young embryos of fish, amphibians, reptiles, birds and mammals show quite similar structure in the early stages.
• As the further growth takes place, they acquire different patterns.
• The initial similarity between the vertebrate embryos is an evidence that during evolution, there was a common ancestor for all the vertebrate classes.
• This is called embryological evidence for vertebrate evolution.
In simple words: Early embryos of various chordates, like fish, amphibians, and mammals, exhibit remarkable structural similarities. These resemblances suggest a shared evolutionary origin and a common ancestor for all vertebrate classes, providing strong embryological evidence for evolution.

🎯 Exam Tip: Highlight the initial similarities in early embryonic stages and how these diverge later, linking this observation directly to the concept of a common ancestor.

 

Question 3. complete the statements by choosing correct options from bracket.
(Genes, Mutation, Translocation, Transcription, Gradual development, Appendix)
a. The causality behind the sudden changes was understood due to Mutation principle of Hugo de Vries.
Answer: (a) Mutation
In simple words: Hugo de Vries proposed the principle of mutation, which explains that sudden, heritable changes in an organism's genetic material are responsible for the variations seen in evolution.

🎯 Exam Tip: For fill-in-the-blank questions, ensure the chosen word fits both the scientific context and the grammatical structure of the sentence.

 

b. The proof for the fact that protein synthesis occurs through Genes was given by George Beadle and Edward Tatum.
Answer: (b) Genes
In simple words: George Beadle and Edward Tatum demonstrated that genes control the synthesis of proteins, establishing a fundamental link between genetic information and biochemical processes in living organisms.

🎯 Exam Tip: Remember key scientists and their contributions to specific biological processes, especially foundational concepts like the gene-protein relationship.

 

c. Transfer of information from molecule of DNA to mRNA is called as Transcription process.
Answer: (c) Transcription
In simple words: Transcription is the process where genetic information encoded in DNA is copied into a messenger RNA (mRNA) molecule. This mRNA then carries the instructions out of the nucleus to the ribosomes for protein synthesis.

🎯 Exam Tip: Distinguish transcription from translation and translocation; transcription is specifically the DNA to mRNA step.

 

d. Evolution means Gradual development
Answer: (d) Gradual development
In simple words: Evolution refers to the slow and continuous process of change in living organisms over successive generations, leading to increased diversity and complexity of life forms.

🎯 Exam Tip: Understand that evolution is a continuous, long-term process involving gradual changes, not sudden transformations.

 

e. Vestigial organ Appendix present in human body is proof of evolution.
Answer: (e) Appendix
In simple words: The appendix is a vestigial organ in humans, meaning it has lost its original function over evolutionary time. Its presence serves as evidence of our evolutionary past, pointing to ancestors where it may have had a digestive role.

🎯 Exam Tip: Be able to identify common vestigial organs in humans and explain why their presence supports the theory of evolution.

 

Question 4. Write short notes based upon the information known to you.
a. Lamarckism.
Answer:
(1) Lamarckism consists of two theories which were proposed by Jean Baptiste Lamarck. These are as follows: (a) Use and disuse of the organs (b) Inheritance of acquired characters.
(2) In theory of use and disuse of organs, Lamarck says : The characters of organs develop because specific activities that the organisms perform. If such organ is not used it gets degenerated. Thus the morphological changes take place due to activities or inactivity of a particular organism.
(3) To emphasise this theory, he quoted following examples. Due to constant extension of neck to eat foliage from the top of the trees, giraffe's neck became long. Similarly blacksmith has strong arms due to constant work. Flightless ostrich and emu did not fly and hence their wings became useless. Aquatic birds like swan and duck made their feet suitable for swimming by living in water. Snake lost limbs as it tried burrowing mode.
(4) Such acquired characters are passed from one parental generation to the offspring. This is called inheritance of acquired characters.
(5) The theory of inheritance of acquired characters is not accepted as such transmission of acquired character does not take place. Only genetic characters are transmitted.
In simple words: Lamarckism, proposed by Jean Baptiste Lamarck, suggested that organisms acquire traits during their lifetime through the use or disuse of organs, and these acquired traits are then passed on to their offspring. While influential, this theory is largely not accepted today as only genetic characters are inherited.

🎯 Exam Tip: Clearly state the two main postulates of Lamarckism and provide classic examples (like giraffe's neck) while also noting why the theory is not widely accepted now.

 

b. Darwin's theory of natural selection.
Answer:
• Charles Darwin proposed the theory of natural selection after making many observations on different specimens. He published a concept 'Survival of the fittest'.
• Darwin explains this concept as follows: All the organisms reproduce prolifically. Therefore, there is always a competition for food, mate, etc. Only adaptations for sustaining this struggle.
• Natural selection plays important role by selecting only those organisms which are fit to live. Those that do not have better adaptations, perish. Selected sustaining organisms then perform reproduction and form new species in a very long period of time.
• Darwin published his views in the book titled 'Origin of Species'.
In simple words: Darwin's theory of natural selection states that individuals with advantageous traits for their environment are more likely to survive, reproduce, and pass those traits to their offspring. Over generations, this process leads to the accumulation of favorable characteristics and the evolution of new species, famously summarized as 'survival of the fittest'.

🎯 Exam Tip: When explaining Darwin's theory, ensure you mention key concepts like overproduction, variation, struggle for existence, and differential survival and reproduction, along with the book 'Origin of Species'.

 

c. Embryology.
Answer:
• Embryology is the study of developing embryos.
• These embryos in their initial stages are very similar to each other.
• These similarities decrease later in the development.
• This similarity in initial stages indicate that these vertebrates have originated from a common ancestor.
• In evolutionary science, comparative study of embryos of various vertebrates provide evidence for evolution.
In simple words: Embryology is the study of embryonic development. The striking similarities in the early embryonic stages of different vertebrates provide strong evidence for a common ancestry, even though these similarities diverge as development progresses.

🎯 Exam Tip: Define embryology and focus on the concept of 'common ancestry' as the main evolutionary implication of embryonic similarities.

 

d. Evolution.
Answer:
• The sequential changes in the groups of living organisms that take place very gradually is called evolution.
• Evolution is also described as the formation of new species due to natural selection.
• The process of evolution takes millions of years for development and speciation of different organisms.
• Changes in stars and planets in space and the changes in biosphere occurring on the Earth are all included under study of evolution.
• Due to evolution organisms become fit, biodiversity is increased, and new species are created.
• Different scientists have put forth theories to explain the process of evolution. Among these Charles Darwin's theory of natural selection and speciation is accepted worldwide.
In simple words: Evolution is the slow, continuous process of change in living organisms over generations, leading to new species and increased biodiversity. It is driven by natural selection, adapting organisms to their environment and resulting in the vast array of life we see today.

🎯 Exam Tip: Provide a concise definition of evolution, its timeframe, and highlight its outcomes like increased biodiversity and fitness of organisms.

 

e. Connecting link.
Answer:
Some living organisms possess some characters in them which are the distinctive features of different groups or phyla. Such individuals connect these two groups by sharing the characters of both and hence they are known as connective links.
Examples: (1) Peripatus: Peripatus is the connecting link between Annelida and Arthropoda. It shows characters of both animal phyla. Like annelid worm, it shows segmented body, thin cuticle and parapodia. Like an arthropod, it shows open circulatory system and tracheal system for respiration.
(2) Duck Billed platypus: This is a connecting link between reptiles and mammals. Like reptiles it lays eggs but like mammals it has mammary glands and hairy skin.
(3) Lung fish: Lung fish is a connecting link between fishes and amphibians. Though a fish, it shows lungs for respiration as in amphibian animals.
(4) Connecting links indicate the direction and hierarchy of evolution.
In simple words: Connecting links are organisms that exhibit characteristics of two different taxonomic groups, providing evolutionary evidence of how one group may have evolved from another. Examples include Peripatus (Annelida and Arthropoda), Duck-billed platypus (Reptiles and Mammals), and Lungfish (Fishes and Amphibians).

🎯 Exam Tip: Define connecting links clearly and provide at least two distinct examples with specific shared characteristics to illustrate their evolutionary significance.

 

Question 5. Define heredity. Explain the mechanism of hereditary changes.
Answer:
(1) Heredity: Heredity is the process by which the biological characters from parental generation are transmitted to the next generation through genes.
(2) The mechanism of hereditary changes:
• Mutation: Sudden change in the parental DNA can cause mutations. This results into changes in the hereditary characters.
• At the time of meiosis, the crossing over takes place. This creates new recombination of the genetic information. Therefore, the haploid gametes produced carry changed hereditary characters.
In simple words: Heredity is the passing of traits from parents to offspring via genes. Hereditary changes occur mainly through mutations (sudden DNA alterations) and genetic recombination during meiosis (crossing over), both of which introduce new variations in the genetic makeup of offspring.

🎯 Exam Tip: A complete answer defines heredity and then clearly explains how mutations and crossing over during meiosis contribute to changes in hereditary characters.

 

Question 6. Define vestigial organs. Write names of some vestigial organs in human body and write the names of those animals in whom same organs are functional.
Answer:
• Vestigial organs are degenerated or underdeveloped organs of organisms which do not perform any function.
• According to the principle of natural selection, such organs are on the verge of disappearance. But it takes many millions of years for its complete vanishing.
• The vestigial organs in one animal may be of use but to other kind of the animal as they still perform regular functions.
• Appendix is vestigial for humans, it does not perform any function but in ruminant animals it is concerned with digestion.
• Ear muscles are vestigial for us but in monkeys and cattle they are functional.
• Names of vestigial organs in human body-Appendix, tail-bone or coccyx, wisdom teeth and body hair.
In simple words: Vestigial organs are body parts that have lost their original function over evolutionary time and are often reduced in size. Examples in humans include the appendix, which is functional in ruminant animals for digestion, and ear muscles, which are functional in monkeys for ear movement.

🎯 Exam Tip: Ensure your definition of vestigial organs is accurate and list at least three human vestigial organs, clearly linking each to an animal where it is still functional.

 

Question 7. Answer the following questions.
a. How are the hereditary changes responsible for evolution?
Answer:
Hereditary characters are transmitted from parental generation to the offspring. These characters are maintained through inheritance. But the genes which are beneficial for the organisms in helping them to adapt to the environment are transmitted to the next generations in a greater proportion. This happens due to natural selection.
The process of evolution happens at a very slow pace. The favourable genes are preserved in the species as they bring about better survival of the individuals. Such individual reproduces more efficiently and evolve. The individuals with unfavourable genes are not selected by nature and are thus removed from the population through natural death. The fuel for evolution is thus truly supplied by the hereditary changes.
In simple words: Hereditary changes, such as mutations and recombinations, introduce genetic variation in offspring. When these changes provide a survival advantage, individuals with these favorable traits are more likely to reproduce and pass them on, driving the process of natural selection and, consequently, evolution.

🎯 Exam Tip: Connect the concepts of hereditary changes (variation) directly to natural selection and improved adaptation, explaining how these collectively lead to evolutionary progress.

 

b. Explain the process of formation of complex proteins.
Answer:
The proteins are synthesised in following steps, viz. transcription, translation and translocation. Protein synthesis takes place according to the sequence of nucleotides present on the DNA molecule with the help of RNA molecules. This is known as central dogma of protein synthesis.
1. Transcription: In the process of transcription, mRNA is produced as per the nucleotide sequence on the DNA. For this the two strands DNA are separated. Only one strand participates in the formation of mRNA. The sequence of nucleotides which is complementary to that of present on DNA is copied on mRNA. Instead of thymine present in DNA, uracil is added on the mRNA. Transcription takes place in nucleus but the mRNA leaves nucleus, carries the genetic code and enters the cytoplasm. This genetic code is always in triplet form arid hence is known as triplet codon. The code for each amino acid always consists of three nucleotides.
2. Translation: Each mRNA may carry thousands of codons. But each codon is specific for only one amino acid. The tRNA molecule brings the required amino acid as per the code present on mRNA. There is anticodon on each tRNA which is complementary to the codon on mRNA. This process is known as translation.
3. Translocation: In translocation, the ribosome keeps on moving from one end of mRNA molecule to other end by distance of one triplet codon. While this process is taking place, rRNA, helps in joining the amino acids together by peptide bonds. The peptide chains later come together to form complex protein molecules.
In simple words: Complex proteins are formed through a three-step process: transcription, translation, and translocation. First, DNA's genetic code is transcribed into mRNA. Then, during translation, tRNA molecules bring specific amino acids to the mRNA codons in the ribosome. Finally, translocation involves the ribosome moving along the mRNA, linking these amino acids with peptide bonds to form protein chains.

🎯 Exam Tip: Clearly define and explain each step-transcription, translation, and translocation-highlighting the role of DNA, mRNA, tRNA, rRNA, and ribosomes in protein synthesis.

 

c. Explain the theory of evolution and mention the proof supporting it.
Answer:
1. Theory of evolution:
• According to the theory of evolution, first living material was in the form of protoplasm which was formed in ocean.
• Gradually, it gave rise to unicellular organisms. Changes took place in these unicellular organisms which made them evolve into larger and more complex organisms.
• All evolutionary changes were very slow and gradual taking about 300 crore years to happen.
• Different types of organisms were developed as the changes and development that occurred in living organisms wefts all round and multi-dimensional.
• Hence, this overall process of evolution is called organizational and progressive.
• Variety of plants and animals developed from the ancestors having different structural and functional organization during the process of evolution.
2. Proof here means evidences of evolution.
These evidences are as follows:
• Morphological evidences
• Anatomical evidences
• Vestigial organs
• Palaentological evidences
• Connecting links
• Embryological evidences.
In simple words: The theory of evolution states that life originated as simple protoplasm in the ocean and gradually diversified into complex organisms over billions of years through slow, continuous changes. This process, driven by natural selection, is supported by various lines of evidence including morphological similarities, anatomical structures, vestigial organs, fossil records (palaeontological), connecting links between groups, and embryological development.

🎯 Exam Tip: When asked to explain the theory of evolution and its proofs, first provide a concise overview of the theory's core idea (gradual change from simple to complex forms) and then list the major categories of evidence that support it.

 

d. Explain with suitable examples importance of anatomical evidences in evolution.
Answer:
• There are similarities in the structure and anatomy of different animal groups. E.g. human hand, forelimb of bull, patagium of bat and flipper of whale are all similar in their internal anatomy. There is similarity in the bones and joints of all these specimens.
• External morphology does not show any similarity. Use of each of the organ is also different in different animals. Structurally, they may not be related.
• However, the similarities in the anatomy is an evidence that they may have a common ancestor.
• In this way, the anatomical evidence throws light on the process of evolution.
In simple words: Anatomical evidences demonstrate evolutionary relationships through similarities in the internal structures of different organisms, even if their external forms and functions vary. For instance, the comparable bone structure in a human hand, a bull's forelimb, a bat's patagium, and a whale's flipper suggests that these diverse species share a common ancestor.

🎯 Exam Tip: Use the classic example of homologous structures (e.g., forelimbs of different mammals) to clearly illustrate how underlying anatomical similarities, despite functional differences, point to a common evolutionary origin.

 

e. Define fossil. Explain importance of fossils as proof of evolution.
Answer:
• Fossils offer palaeontological evidence for the evolutionary process.
• Due to some natural calamities the organisms get buried during ancient times.
• The impressions and remnants of such organisms remain preserved underground. The hot lava also traps some organisms or their impressions. All such formations form fossils.
• Study of fossils help the researcher to understand the characteristics of the organisms that existed in the.past.
• Carbon dating method also helps in finding out exact age of the fossil. According to the structure of earth's crust the fossils are obtained at specific depths.
• The oldest ones are obtained at the depth while the relatively recent ones occupy the upper surface. Thus fossils of invertebrates were seen in very old Palaeozoic era. Later were seen fossils of Pisces, Amphibia and Reptilia. The Mesozoic era was dominated by reptiles while Coenozoic era showed presence of mammals.
• In this way, study of fossils unfold the evolutionary secrets.
In simple words: Fossils are the preserved remains or impressions of ancient organisms, typically found in sedimentary rocks. They are crucial proofs of evolution because they show a chronological record of life, revealing past species, their characteristics, and how they changed over geological time, with carbon dating helping to determine their age.

🎯 Exam Tip: Define fossil accurately, then elaborate on their significance by discussing their role in establishing geological timelines, showing transitional forms, and providing evidence for past biodiversity and extinction events.

 

f. Write evolutionary history of modern man.
Answer:
(1) Ancestors of humans developed from animals which resembled lemur-like animals.
(2) Around seven crore years ago, monkey-like animals evolved from some of these lemur-like animals.
(3) Then after about 4 crore years ago, in Africa the tails of these monkey-like creatures very gradually disappeared.
(4) Simultaneously, there was enlargement in their body and brain volume too. The hands also improved and were provided with opposable thumb. In this way, ape-like animals were evolved.
(5) These ape-like animals independently gave rise to two lines of evolution, one giving rise to apes like gibbon and orangutan in the South and North-East Asia and gorilla and chimpanzee which stayed in Africa around 2.5 crores of years ago.
(6) The other line of evolution gave rise to human-like animals around 2 crore years ago.
(7) The climate became dry and this resulted into reduction of forest cover. This made arboreal apes to descend on the land and start terrestrial mode.
(8) Due to this, there were changes in the pefvic girdle and vertebral column. The hands were also freed from locomotion and thus they became more manipulative.
(9) Later, journey of hominoid species started from around 2 crores years ago. The first record of human-like animal is 'Ramapithecus' ape from East Africa.
(10) Ramapithecus
\( \implies \) Australopithecus
\( \implies \) Neanderthal man
\( \implies \) Cro-Magnon are the important steps in human evolution.
(11) Neanderthal man was said to be the first wise man. The increasing growth of brain made man more and more intelligent and thinking animal.
(12) Later, more than biological evolution, it was cultural evolution, when man started agriculture, animal, rearing. There was development of civilizations, arts and science etc. About 200 years ago there were industrial inventions and thus man now rules the earth.
In simple words: Modern human evolutionary history began around 7 crore years ago with lemur-like ancestors, leading to monkey-like animals, then ape-like forms with increased brain size and opposable thumbs. A key step was the shift to terrestrial living, freeing hands for manipulation. Key species like Ramapithecus, Australopithecus, Neanderthal, and Cro-Magnon mark stages, with cultural evolution and intelligence accelerating progress.

🎯 Exam Tip: Present the evolutionary history chronologically, mentioning key ancestral forms (e.g., Lemur-like, Ramapithecus, Australopithecus, Neanderthal, Cro-Magnon), important physical changes (e.g., tail disappearance, brain enlargement, upright posture, manipulative hands), and the development of cultural aspects.

 

Can You Recall? (Text Book Page No. 1)

 

Question 1. Which component of the cellular nucleus of living organisms carries hereditary characters?
Answer:
The chromosomes made up of nucleic acids and proteins, present in the nucleus of the cell are the components that carry hereditary characters in living organisms.
In simple words: Chromosomes, found in the cell's nucleus and composed of nucleic acids (DNA) and proteins, are the structures responsible for carrying hereditary characters in living organisms.

🎯 Exam Tip: Remember that chromosomes are the main carriers of genetic information, with DNA being the actual hereditary material they contain.

 

Question 2. What do we call the process of transfer of physical and mental characters from parents to the progeny?
Answer:
The process of transfer of physical and mental characters from parents to the progeny is called inheritance or heredity.
In simple words: The process by which physical and mental characteristics are passed from parents to their offspring is known as inheritance or heredity.

🎯 Exam Tip: Use either "inheritance" or "heredity" as both terms accurately describe the passing of traits from one generation to the next.

 

Question 3. Which are the components of the DNA molecule?
Answer:
DNA molecule is made up of two helical strands consisting of deoxyribose sugar, phosphoric acid and pairs of nitrogenous bases. These three together is called a nucleotide.
In simple words: A DNA molecule is composed of two helical strands, each made up of repeating units called nucleotides. Each nucleotide consists of three main components: a deoxyribose sugar, a phosphate group (phosphoric acid), and one of four nitrogenous bases (adenine, guanine, cytosine, or thymine).

🎯 Exam Tip: To answer this correctly, list the three primary components of a nucleotide: deoxyribose sugar, phosphoric acid (phosphate group), and nitrogenous bases, and mention the double helical structure.

 

Choose The Correct Alternative And Write Its Alphabet Against The Sub-Question Number:

 

Question 1. Darwin has published a book titled ..........
(a) Natural selection
(b) Mutation
(c) Fall of a sparrow
(d) Origin of species
Answer: (d) Origin of species
In simple words: Charles Darwin's seminal work, which laid out his theory of evolution by natural selection, was published in the book titled 'On the Origin of Species by Means of Natural Selection'.

🎯 Exam Tip: Knowing the full and correct title of Darwin's famous book is essential for questions related to the history of evolutionary theory.

 

Question 2. The Cro Magnon man evolved about 50 thousand years ago.
(a) Cro Magnon
(b) Neanderthal
(c) Java man
(d) Ramapithecus
Answer: (a) Cro Magnon
In simple words: The Cro-Magnon man, an early modern human, is known to have evolved approximately 50,000 years ago.

🎯 Exam Tip: Chronology of human evolution is key; remember the approximate timelines associated with different early human species.

 

Question 3. About 10 thousand years ago, wise man started to practise agriculture.
(a) Gorilla
(b) wise man
(c) Ramapithecus
(d) Australopithecus
Answer: (b) wise man
In simple words: Approximately 10,000 years ago, "wise man" (Homo sapiens) transitioned from nomadic lifestyles to settled communities by beginning to practice agriculture.

🎯 Exam Tip: Connect the development of agriculture with the "wise man" or Homo sapiens, marking a significant shift in human societal development.

 

Question 4. Neanderthal man can be considered as the first example of wise-man.
(a) Australopithecus
(b) Ramapithecus
(c) Cro Magnon
(d) Neanderthal man
Answer: (d) Neanderthal man
In simple words: The Neanderthal man is often considered the first example of a wise-man due to their advanced tool-making, burial practices, and evidence of complex social structures.

🎯 Exam Tip: Understand the characteristics and evolutionary significance of different hominid species, especially regarding the development of intelligence and 'wisdom'.

 

Question 5. Peripatus is a connecting link between Annelida and Arthropoda.
(a) Duck-billed platypus
(b) Peripatus
(c) Lung fish
(d) Whale
Answer: (b) Peripatus
In simple words: Peripatus is a classic example of a connecting link, showing features of both annelids (segmented body, thin cuticle) and arthropods (tracheal respiration, open circulatory system).

🎯 Exam Tip: Memorize key examples of connecting links and the two animal phyla they link, as these are common MCQ questions.

 

Question 6. 50,000 years ago human brain was sufficiently evolved to call him wise man.
(a) 50,000
(b) 30,000
(c) 20,000
(d) 10,000
Answer: (a) 50,000
In simple words: It was approximately 50,000 years ago that the human brain had developed sufficiently to categorize Homo sapiens as "wise man," enabling complex thought and behaviors.

🎯 Exam Tip: Pay attention to the specific timeframes associated with major milestones in human evolution, especially those related to brain development and classification as "wise man."

Question 7. The process by which the gene in the nucleotide suddenly changes its position is called ..........
Answer: (c) mutation
In simple words: A mutation is a sudden, random change in the DNA sequence that can alter genetic information.

🎯 Exam Tip: Understanding the basic definitions of genetic processes like mutation, translation, and transcription is crucial for multiple-choice questions.

Question 8. .......... is not the vestigial organ in the human body.
Answer: (c) Canine
In simple words: Canine teeth are functional in humans, unlike vestigial organs which are degenerated and non-functional remnants from ancestors.

🎯 Exam Tip: Be able to identify common vestigial organs in humans and distinguish them from functional body parts.

Write Whether The Following Statements Are True Or False With Proper Justification For Your Answer:

Question 1. It takes thousands of years for a useful structure to disappear.
Answer: False. (The useful structures of the body do not disappear. The functioning of the body is easier due to such organs. It takes thousands of years for a functionless organ to disappear.)
In simple words: Useful body structures persist because they contribute to survival, while non-functional vestigial organs may slowly disappear over long evolutionary periods.

🎯 Exam Tip: Focus on the concept of natural selection; useful traits are conserved, while non-useful ones are gradually lost.

Question 2. Dr. Har Govind Khorana was awarded Nobel prize for his invention and publication in the journal Radio carbon.
Answer: False. (Willard Libby was awarded Nobel prize for his invention and publication in the journal Radio carbon.)
In simple words: The Nobel Prize for the discovery of radiocarbon dating was awarded to Willard Libby, not Dr. Har Govind Khorana, who was recognized for his work on genetic code.

🎯 Exam Tip: Remember the key contributions of important scientists in the field of genetics and evolution, especially their major discoveries or theories.

Question 3. Mesozoic era was dominated by variety of mammals.
Answer: False. (Mesozoic era dominated by variety of reptiles.)
In simple words: The Mesozoic era is widely known as the "Age of Reptiles" due to the dominance of dinosaurs and other large reptiles during that period.

🎯 Exam Tip: Be familiar with the characteristic life forms and dominant species of different geological eras to correctly answer questions about evolutionary timelines.

Question 4. It seems that invertebrates have been slowly originated from vertebrates.
Answer: False. (Vertebrates have been slowly originated from invertebrates in course of evolution. The primitive type of organisms always give rise to complex life forms. The invertebrates from Palaeozoic era gradually gave rise to vertebrates.)
In simple words: Evolution progresses from simpler to more complex forms, meaning invertebrates appeared earlier and vertebrates evolved from them, not the other way around.

🎯 Exam Tip: Understand the general direction of evolutionary progression from simpler (invertebrates) to more complex (vertebrates) life forms.

Question 5. The decaying process of C-12 occurs continuously from the dead remains of living organisms.
Answer: False. (The decaying process of C-14 occurs continuously from the dead remains of living organisms. C-12 is not radioactive and hence it does not show decaying process.)
In simple words: Carbon-14 (C-14), a radioactive isotope, decays in dead organisms, while Carbon-12 (C-12) is stable and does not decay, making C-14 crucial for carbon dating.

🎯 Exam Tip: Distinguish between the roles of C-14 and C-12 in carbon dating, emphasizing the radioactive nature of C-14.

Question 6. The theory of natural selection which mentions 'Survival of fittest' is given by Lamarck.
Answer: False. (The theory of natural selection which mentions 'Survival of fittest' is given by Darwin.)
In simple words: Charles Darwin proposed the theory of natural selection, which includes the concept of 'survival of the fittest', distinguishing it from Lamarck's theory of acquired characteristics.

🎯 Exam Tip: Clearly differentiate between Darwin's theory of natural selection and Lamarck's theory of inheritance of acquired characters.

Question 7. Changes acquired during life time are transferred to next generation.
Answer: False. (Changes acquired during life time are not heritable. They are not transferred to next generation. Only the genes are transferred to the next generation.)
In simple words: Acquired characteristics, developed during an organism's lifetime, are generally not passed on to offspring, as only genetic information is inherited.

🎯 Exam Tip: Understand that only genetically determined traits are heritable, not traits acquired through experience or environmental influence during an individual's life.

Question 8. Each species grows in specific geographical conditions and has specific food, habitat, reproductive ability and period.
Answer: True. (Each species has specifically evolved characters due to evolution and speciation.)
In simple words: Every species is adapted to particular environmental conditions, including its specific diet, living space, and reproductive cycle, which arise from evolutionary processes.

🎯 Exam Tip: Recognize that species develop unique adaptations and characteristics, including their niche and reproductive strategies, through evolutionary processes like natural selection and speciation.

Question 9. Humans walking with upright posture were confined to Africa only during prehistoric period.
Answer: False. (Humans walking upright existed in Africa and China, Indonesia of Asian continent too.)
In simple words: Evidence suggests that early humans with upright posture migrated out of Africa, indicating their presence in other regions like Asia during the prehistoric period.

🎯 Exam Tip: Be aware of the broader geographical spread of early human evolution and migration, not just focusing on Africa.

Question 10. Industrial society was established about 200 years ago.
Answer: True. (After the development and specialization of human brain, he started indulging in science and technology. Before; this period the idea of industrialization was not existing.)
In simple words: The Industrial Revolution, which marked the beginning of industrial society, commenced around 200-250 years ago, following significant advancements in human intellect and technology.

🎯 Exam Tip: Connect major historical periods, like the Industrial Revolution, to the timeline of human cognitive and technological evolution.

Match The Columns:

Question 1.

Scientist	Discovery
(1) Johann Gregor Mendel	(a) Chromosomes of grasshopper
(2) Hugo de Vries	(b) DNA is genetic material
	(c) Pioneer of the modern genetics
	(d) Mutational theory

Answer:
(1) Johann Gregor Mendel - Pioneer of the modern genetics.
(2) Hugo de Vries - Mutational theory.
In simple words: Mendel is known as the father of modern genetics for his work on inheritance, while Hugo de Vries proposed the mutation theory of evolution.

🎯 Exam Tip: Memorize the contributions of key scientists to genetics and evolution, particularly their main theories or discoveries.

Question 2.

Scientist	Discovery
(1) Walter, Sutton	(a) Chromosomes of grasshopper
(2) Mclyn McCarthy	(b) DNA is genetic material
	(c) Pioneer of the modern genetics
	(d) Mutational theory

Answer:
(1) Walter, Sutton - Chromosomes of grasshopper.
(2) Mclyn McCarthy - DNA is genetic material.
In simple words: Sutton's work on grasshopper chromosomes linked inheritance to chromosomes, while Avery, MacLeod, and McCarty famously proved that DNA is the genetic material.

🎯 Exam Tip: Associate specific discoveries, like the chromosomal theory of inheritance or the identification of DNA as genetic material, with the scientists who made them.

Question 3.

Evidences of evolution	Examples
(1) Morphological evidences	(a) Duck billed Platypus and Peripatus
(2) Anatomical evidences	(b) Remnants and impressions
	(c) Human hand and fore limb of bull
	(d) Shape and venation of leaf

Answer:
(1) Morphological evidences - Shape and venation of leaf.
(2) Anatomical evidences - Human hand and fore limb of bull.
In simple words: Morphological evidence compares external features like leaf shape, while anatomical evidence compares internal structures, such as the bone structure of a human hand and a bull's forelimb, to show common ancestry.

🎯 Exam Tip: Differentiate between morphological (external similarities) and anatomical (internal structural similarities) evidences for evolution and be ready with relevant examples for each.

Question 4.

Evidences of evolution	Examples
(1) Palaeontological evidences	(a) Duck billed Platypus and Peripatus
(2) Connecting links	(b) Remnants and impressions
	(c) Coccyx and wisdom tooth
	(d) Human hand and fore limb of cat

Answer:
(1) Palaeontological evidences - Remnants and impressions.
(2) Connecting links - Duck billed Platypus and Peripatus.
In simple words: Palaeontological evidence relies on fossils (remnants and impressions of past life), while connecting links are organisms like the Duck-billed Platypus or Peripatus that show traits of two different groups, indicating evolutionary transitions.

🎯 Exam Tip: Clearly define palaeontological evidence and connecting links, providing distinct examples for each as proof of evolution.

Find The Odd One Out:

Question 1. Transcription, Translation, Translocation, Mutation
Answer: Mutation. (All others are stages of protein synthesis.)
In simple words: Transcription, translation, and translocation are sequential steps in creating proteins from genetic information, whereas mutation is a change in the genetic code itself.

🎯 Exam Tip: Understand the central dogma of molecular biology and recognize the key processes involved in protein synthesis to identify unrelated terms.

Question 2. Bones of the hands, structure of nostrils, position of eyes, structure of ear pinnae
Answer: Bones of the hands. (All the others are morphological evidences.)
In simple words: While bones of the hands provide anatomical evidence for shared ancestry, external features like nostrils, eye position, and ear pinnae are considered morphological similarities.

🎯 Exam Tip: Distinguish between morphological evidences (external similarities) and anatomical evidences (internal structural similarities) in evolutionary studies.

Question 3. Venation, Shape of seeds, Leaf petiole, Leaf shape
Answer: Shape of seeds. (All the others are morphological evidences in plants.)
In simple words: Leaf venation, petiole, and shape are visible external features used as morphological evidence in plants, but seed shape is an internal, reproductive characteristic.

🎯 Exam Tip: When analyzing plant features for evolutionary evidence, recognize which traits are external (morphological) versus internal or reproductive.

Question 4. Human hand, wing of cockroach, forelimb of bull, flipper of whale
Answer: Wing of cockroach. (All others are anatomical evidences, they are homologous organs.)
In simple words: The human hand, bull's forelimb, and whale's flipper are homologous structures with similar bone arrangements, indicating a common ancestor, unlike the wing of a cockroach which has a different evolutionary origin and structure (analogous organ).

🎯 Exam Tip: Understand the difference between homologous organs (shared ancestry, different function) and analogous organs (different ancestry, similar function) as evidence of evolution.

Identify The Correlation Between The First Two Words And Suggest The Suitable Words In The Fourth Place:

Question 1. mRNA : Transcription :: tRNA :............
Answer: Translation
In simple words: mRNA is produced during transcription, while tRNA plays a crucial role in the process of translation by carrying amino acids to the ribosome.

🎯 Exam Tip: Know the specific roles of different types of RNA (mRNA, tRNA, rRNA) in the processes of transcription and translation.

Question 2. Peripatus: Connecting link :: Appendix :.........
Answer: Vestigial organs
In simple words: Peripatus is an example of a connecting link, showing evolutionary ties between two groups, just as the appendix in humans is a vestigial organ, a remnant of a functional organ in ancestors.

🎯 Exam Tip: Be able to classify evolutionary evidences, such as connecting links and vestigial organs, and provide relevant examples for each.

Question 3. Open circulatory system : Arthropods :: Thin cuticle and parapodia :...........
Answer: Annelida
In simple words: Arthropods typically have an open circulatory system, while Annelids are characterized by a thin cuticle and parapodia (in some, like polychaetes).

🎯 Exam Tip: Recall the distinguishing characteristics of different animal phyla, especially those that serve as evolutionary evidence like Peripatus.

Question 4. Between Annelida and Arthropoda : Peripatus :............ Lungfish
Answer: Pisces/Fish and Amphibia
In simple words: Peripatus is a connecting link between Annelida and Arthropoda, similarly, the Lungfish is a connecting link between fishes (Pisces) and amphibians.

🎯 Exam Tip: Identify key "connecting link" organisms and the two groups of animals they connect, highlighting their transitional evolutionary significance.

Question 5. Theory of natural selection : Charles Robert Darwin :: Theory of inheritance of acquired characters :.............
Answer: Jean Baptiste Lamarck
In simple words: Charles Darwin proposed the theory of natural selection, while Jean Baptiste Lamarck is known for his theory of inheritance of acquired characters.

🎯 Exam Tip: Clearly associate major evolutionary theories with their respective proponents, such as Darwin with natural selection and Lamarck with acquired inheritance.

Question 6. Survival of fittest : Darwin :: Acquired characters :..........
Answer: Lamarck
In simple words: The concept of 'survival of the fittest' is central to Darwin's theory, just as the idea of 'acquired characters' is fundamental to Lamarck's evolutionary theory.

🎯 Exam Tip: Understand the core concepts associated with each major evolutionary theory and their respective scientists.

Question 7. Wisdom teeth : Vestigial organs :: Lungfish...........
Answer: Connecting link.
In simple words: Wisdom teeth are considered vestigial organs in humans, whereas Lungfish are recognized as a connecting link between fish and amphibians due to their unique features.

🎯 Exam Tip: Differentiate between examples of vestigial organs and connecting links, and explain why each provides evidence for evolution.

Define The Following:

Question 1. Heredity.
Answer: The transfer of biological characters from one generation to another through genes is called heredity.
In simple words: Heredity is the process by which traits are passed down from parents to their children via genes.

🎯 Exam Tip: A precise definition of heredity is essential, emphasizing the role of genes in transmitting characters across generations.

Question 2. Transcription.
Answer:
In simple words: Transcription is the process where genetic information from DNA is copied into an RNA molecule.

🎯 Exam Tip: Focus on transcription as the initial step in gene expression, converting DNA's genetic message into an RNA format.

Question 3. Translation.
Answer: The process of bringing tRNA possessing anticodon that is complementary to the codon on mRNA for protein synthesis is called translation.
In simple words: Translation is the process where the genetic code carried by mRNA is read by tRNA to synthesize proteins by linking specific amino acids.

🎯 Exam Tip: Highlight the role of mRNA codons and tRNA anticodons in accurately assembling amino acids during protein synthesis.

Question 4. Translocation.
Answer:
In simple words: Translocation in molecular biology refers to the movement of the ribosome along the mRNA strand during protein synthesis, one codon at a time.

🎯 Exam Tip: Understand translocation as the directional movement of the ribosome, which ensures sequential reading of codons and polypeptide chain elongation.

Question 5. Mutation.
Answer: Sudden and drastic change that occurs in the genetic material is called mutation.
In simple words: A mutation is any abrupt, significant alteration in an organism's genetic material, such as DNA.

🎯 Exam Tip: Define mutation clearly as a fundamental source of genetic variation and a driving force for evolution.

Question 6. Species.
Answer: The group of organisms that can produce fertile individuals through natural reproduction is called a species.
In simple words: A species is a group of organisms capable of interbreeding to produce fertile offspring under natural conditions.

🎯 Exam Tip: Remember the biological species concept, emphasizing the ability to interbreed and produce fertile offspring as a key criterion.

Name The Following:

Question 1. Three Scientists who proved that except viruses, all living organisms have DNA as genetic material.
Answer: Oswald Avery, Mclyn McCarthy and Colin MacLeod.
In simple words: Avery, MacLeod, and McCarty conducted experiments that definitively showed DNA, not protein, carries genetic information in most living organisms.

🎯 Exam Tip: Familiarize yourself with the names of scientists and their pivotal experiments that established DNA as the genetic material.

Question 2. Genetic disorder caused due to mutation:
Answer: Sickle cell anaemia.
In simple words: Sickle cell anaemia is a genetic disorder resulting from a single gene mutation that affects the shape of red blood cells.

🎯 Exam Tip: Be able to provide examples of genetic disorders caused by mutations, with sickle cell anaemia being a common and clear illustration.

Question 3. Fish that can breathe with help of lungs:
Answer: Lung fish.
In simple words: Lungfish are unique fish that possess lungs in addition to gills, allowing them to breathe air and survive in oxygen-poor waters.

🎯 Exam Tip: The Lungfish is an important example of a "connecting link" between aquatic and terrestrial vertebrates due to its dual respiratory system.

Question 4. Vestigial organs in human beings:
Answer: Appendix, tail-bone or coccyx, wisdom teeth and body hair.
In simple words: Vestigial organs in humans are non-functional remnants of structures that were important in our evolutionary ancestors, such as the appendix, coccyx, wisdom teeth, and body hair.

🎯 Exam Tip: Know several examples of vestigial organs in humans and understand why their presence supports the theory of evolution.

Question 5. Important stages in the journey of human evolution:
Answer:
• Animals like Lemur
• Egyptopithecus
• Dryopithecus
• Ramapithecus
• Australopithecus
• Skilled Human
• Homo erectus i.e. Man with erect posture
• Neanderthal man
• Cro-Magnon man.
In simple words: Human evolution progressed through various stages, starting from lemur-like ancestors to early apes (like Egyptopithecus, Dryopithecus), followed by hominids (Ramapithecus, Australopithecus), and eventually leading to different forms of Homo (Homo erectus, Neanderthal, Cro-Magnon).

🎯 Exam Tip: Memorize the sequence of key stages and species in the evolutionary lineage of modern humans.

Distinguish Between The Following:

Question 1. Transcription and Translation.
Answer:

Feature	Transcription	Translation
1. Process	In the process of transcription, the sequence of nucleotides present on the DNA molecule is copied and carried to the cytoplasm by mRNA.	In the process of translation, the specific amino acids are picked up according to the codons brought by mRNA.
2. Location	The process of transcription takes place in nucleus.	The process of translation takes place in ribosomes located in cytoplasm.
3. During process	During transcription, RNA is produced from DNA.	During translation, proteins are produced with the help of RNA.
4. RNA types involved	Only mRNA takes part in transcription.	mRNA, tRNA and rRNA take part in translation.

In simple words: Transcription is the DNA-to-RNA copying process in the nucleus, while translation is the RNA-to-protein synthesis process occurring in the cytoplasm (ribosomes).

🎯 Exam Tip: Clearly differentiate between transcription and translation based on their location, raw materials, products, and the specific types of RNA involved.

Question 2. Ape and Human.
Answer:
Ape:
1. Brain of the apes is smaller in size.
2. Ape cannot walk upright.
3. Ape is less intelligent as compared to human.
4. Apes are arboreal in their habitat and they spend more time on the trees.
5. The forelimbs of ape are longer than the hind limbs.
Human:
1. Brain of humans is larger in size.
2. Humans can walk upright.
3. Human is considered to be the most intelligent animal.
4. Humans are terrestrial in their habitat. They cannot stay on the trees.
5. The forelimbs of humans are shorter than the hind limbs.
In simple words: Humans have a larger brain, upright posture, terrestrial habitat, and shorter forelimbs compared to apes, which generally have smaller brains, knuckle-walk, are arboreal, and have longer forelimbs.

🎯 Exam Tip: Be able to list distinct morphological, intellectual, and locomotory differences between apes and humans, highlighting evolutionary divergence.

Give Scientific Reasons:

Question 1. Some of the characters of parents are seen in their offspring.
Answer:
• The parental genes are transferred to their progeny through male and female gametes.
• These genes carry hereditary characters.
• Since they are transmitted from the parents to their offspring, one can see the parental characters in their offspring.
In simple words: Offspring inherit traits from their parents because genetic information, encoded in genes, is passed down through reproductive cells (gametes) from one generation to the next.

🎯 Exam Tip: Explain the mechanism of inheritance by detailing how genes, carried by gametes, ensure the transmission of hereditary characters from parents to offspring.

Question 2. Darwin's work on evolution has been a milestone.
Answer:
(1) Darwin has proposed two very important theories of evolution, viz. Theory of natural selection and Theory of origin of species.
(2) The evolution has taken place on the earth for last many crores of years.
(3) The exact nature and process of these evolutionary changes become clear after studying Darwinism. (4) The observations made by Darwin at that time are now tested according to the modern development in science and are found to be correct. Thus, his work is said to be a milestone.
In simple words: Darwin's work, especially his theory of natural selection, provided a clear, evidence-based mechanism for evolution that transformed our understanding of life's diversity and adaptation, laying the foundation for modern biology.

🎯 Exam Tip: Highlight the revolutionary impact of Darwin's theories (natural selection and origin of species) in explaining evolutionary processes and their enduring relevance in modern science.

Question 3. Peripatus is said to be a connecting link between Annelida and Arthropoda.
Answer:
• Peripatus shows segmented body, thin cuticle, and parapodia-like organs.
• These characters are typical of Annelids.
• Similarly, it also shows tracheal respiration and open circulatory system which is a characteristic feature of Arthropods.
• Since Peripatus shares both these characters, it is said to be a connecting link between Annelida and Arthropoda.
In simple words: Peripatus is a connecting link because it exhibits traits common to both annelids (segmented body, thin cuticle) and arthropods (tracheal respiration, open circulatory system), demonstrating an evolutionary transition.

🎯 Exam Tip: When explaining connecting links, clearly list the specific characteristics an organism shares with two different groups to justify its classification as a transitional form.

Question 4. Vertebrates have been slowly originated from invertebrates.
Answer:
• When the carbon dating method was used to assess the age of fossils, it was understood that invertebrates were present on the earth much before the vertebrates.
• The fossils of invertebrates are present in lower layers of earth's strata.
• They were seen in Palaeozoic era of geological time period. Vertebrates dominated during Coenozoic era.
• Their fossils are seen in the upper strata of the earth's crust.
• The structural complexity also increased in vertebrates. All these facts indicate that Vertebrates have slowly originated from invertebrates.
In simple words: Fossil evidence and carbon dating show that simpler invertebrates appeared earlier in geological time and are found in older rock layers, while more complex vertebrates appeared later in newer layers, supporting their evolution from invertebrate ancestors.

🎯 Exam Tip: Use fossil evidence and principles of stratigraphy (rock layers) to explain the chronological appearance of invertebrates before vertebrates, indicating an evolutionary link.

Question 5. During human evolution the hands became available for use.
Answer:
• During human evolution, the climate of earth started becoming dry.
• This resulted in loss of forest cover.
• The apes which were arboreal on the trees thus descended and started walking on land.
• The lumbar bones underwent change and the apes started walking upright on the grasslands.
• The vertebral column also underwent change. Due to upright posture the forelimbs were freed from locomotion.
• The legs started bearing the weight of the body and the hands became available for use.
In simple words: As early human ancestors moved from trees to grasslands and adopted an upright posture, their forelimbs were no longer needed for locomotion, freeing them for manipulating objects and tool use, a key step in human evolution.

🎯 Exam Tip: Connect environmental changes (drying climate, forest loss) with anatomical adaptations (upright posture, changes in vertebral column/limbs) that led to the freeing of hands during human evolution.

Read The Following Statements And Justify The Same In Your Own Words With The Help Of Suitable Examples:

Question 1. Geographical and reproductive isolation of organisms gradually leads to speciation.
Answer:
• Every species survives in specific geographical conditions. The requirements of food and habitat, is specific for each species. Their reproductive ability and period is also different.
• Therefore, the individuals from one species cannot reproduce with individuals from other species.
• When they are separated by a distance or geographical barriers they are said to be isolated geographically.
• When they cannot reproduce with each other, they are said to be isolated reproductively.
• The ancestor species of both these subspecies may be the same but due to isolation over a very long-time duration, there is genetic variation between the two. Therefore, the isolation leads to speciation.
In simple words: When populations of a species are separated by physical barriers (geographical isolation) or can no longer interbreed (reproductive isolation), they evolve independently, accumulating genetic differences over time until they become distinct species.

🎯 Exam Tip: Explain speciation by detailing how geographical barriers lead to distinct evolutionary paths, causing reproductive isolation and eventually the formation of new species.

Question 2. Study of fossils is an important aspect of study of evolution.
Answer:
(1) Fossils offer palaeontological evidence for the evolutionary process.
(2) Due to some natural calamities the organisms get buried during ancient times.
(3) The impressions and remnants of such organisms remain preserved underground. The hot lava also traps some organisms or their impressions. All such formations form fossils.
(4) Study of fossils help the researcher to understand the characteristics of the organisms that existed in the past.
(5) Carbon dating method also helps in finding out exact age of the fossil. According to the structure of earth's crust the fossils are obtained at specific depths.
(6) The oldest ones are obtained at the depth while the relatively recent ones occupy the upper surface. Thus fossils of invertebrates were seen in very old Palaeozoic era. Later were seen fossils of Pisces, Amphibia and Reptilia. The Mesozoic era was dominated by reptiles while Coenozoic era showed presence of mammals.
(7) In this way, study of fossils unfold the evolutionary secrets.
ℹ️ चित्र व्याख्या (Diagram Explanation): इस चित्र में विभिन्न जीवाश्मों की तस्वीरें दिखाई गई हैं, जिनमें डायनासोर और अन्य प्राचीन जीवों के कंकाल अवशेष शामिल हैं। ये जीवाश्म विकास के पुरातात्विक साक्ष्य (पैलियोन्टोलॉजिकल एविडेंस) के रूप में कार्य करते हैं।
In simple words: Fossils provide direct evidence of past life forms, showing how organisms have changed over millions of years and allowing scientists to trace evolutionary lineages and estimate ages using methods like carbon dating.

🎯 Exam Tip: Emphasize how fossils act as a historical record, illustrating evolutionary transitions and showing the presence of organisms from different geological periods, further supported by dating techniques.

Question 3. Among different chordates there are embryological evidences.
Answer:
• Very young embryos of fish, amphibians, reptiles, birds and mammals show quite similar structure in the early stages.
• As the further growth takes place, they acquire different patterns.
• The initial similarity between the vertebrate embryos is an evidence that during evolution, there was a common ancestor for all the vertebrate classes.
• This is called embryological evidence for vertebrate evolution.
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र विभिन्न कशेरुकियों (मछली, सैलामैंडर, कछुआ, चूज़ा, सुअर, बछड़ा, खरगोश, मानव) के भ्रूणीय विकास के विभिन्न चरणों को दिखाता है। प्रारंभिक अवस्थाओं में सभी भ्रूण अत्यधिक समान दिखते हैं, जो विकास के साथ-साथ भिन्न होते जाते हैं।
In simple words: The striking similarities in the early embryonic stages of different vertebrate chordates suggest they share a common ancestor, providing strong embryological evidence for evolution.

🎯 Exam Tip: Explain embryological evidence by highlighting the shared developmental patterns among diverse vertebrates, indicating their evolutionary relatedness from a common ancestor.

Question 4. Human evolution began approximately 7 crore years ago.
Answer:
• Approximately around 7 crore years back the ice age began on the earth. In such conditions, dinosaurs became extinct. The evolution and diversity of mammals started during this time. Due to change in climate the forest cover also declined rapidly.
• Ancestors of monkey-like animals were Lemur like animals which evolved during this time period.
• The tails of these monkey-like creatures started vanishing very gradually around 4 crore years ago.
• The body and brain both increased in volume forming first ape like animals. The monkey like ancestors gave rise to two evolutionary links to apes and human like animals.
• Later, the human evolution took place by changes in the brain volume, the ability to walk upright, excessive use of hand for manipulations.
• This journey of human evolution began 7 crore years ago. But the true wise and intelligent man arose around 50,000 years ago.
In simple words: Human evolution traces back about 70 million years to lemur-like ancestors, with key developments like the disappearance of tails, increased brain size, bipedalism, and enhanced hand manipulation leading to the emergence of modern humans much later.

🎯 Exam Tip: Outline the major evolutionary milestones in human history, connecting environmental changes (like the ice age) to subsequent adaptations and the timeline of hominid development.

 

Question 5.
Answer the following questions:
(a) Describe briefly the Darwin's theory of natural selection.
Answer:
Charles Darwin (1809-1882) proposed the theory of natural selection. Theory of natural selection: 'The survival of fittest', i.e., organisms which are fit for survival, evolve while those that are not, perish. The natural selection thus acts to produce new species.
In simple words: Darwin's theory of natural selection states that organisms best adapted to their environment are more likely to survive and reproduce, passing on their advantageous traits, leading to the formation of new species over time.

🎯 Exam Tip: Focus on the key concept of 'survival of the fittest' and how it drives the production of new species in Darwin's theory.

 

(b) What were the objections raised against Darwinism?
Answer:
Objections raised against Darwinism:
(1) There are other factors too for evolution and just not the Natural Selection.
(2) Arrival of useful and useless modifications were not explained by Darwin, though he said about the survival of the fittest.
(3) He has not given any explanation about slow changes and abrupt changes occurring during evolution.
In simple words: Criticisms of Darwinism include its limited explanation for all evolutionary factors beyond natural selection, its inability to account for the origin of useful and useless modifications, and a lack of explanation for both gradual and sudden evolutionary changes.

🎯 Exam Tip: Be precise when listing the three main objections to Darwin's theory to secure full marks.

 

(c) Which book was published by Darwin to explain this theory?
Answer:
Charles Darwin wrote the book 'Origin of Species'.
In simple words: Charles Darwin's groundbreaking theory of evolution by natural selection was published in his famous book, 'Origin of Species'.

🎯 Exam Tip: Remember the full title of Darwin's pivotal work, 'Origin of Species', as it is a frequent objective question.

 

Question 6.
What were the objections raised against Darwinism?
Answer:
Some of the main objections raised against Darwinism are as follows:
(1) There are other factors too for evolution and just not the Natural Selection.
(2) Arrival of useful and useless modifications were not explained by Darwin, though he said about the survival of the fittest.
(3) He has not given any explanation about slow changes and abrupt changes occurring during evolution.
In simple words: Key objections to Darwinism included its incomplete explanation of all evolutionary factors, its failure to clarify how modifications (useful or not) emerged, and its limited insight into both slow and sudden evolutionary changes.

🎯 Exam Tip: When discussing objections, provide distinct points rather than general statements to demonstrate a clear understanding of the criticisms leveled against Darwin's theory.

 

Question 7.
Answer the following questions:
(a) Explain in brief-Lamarck's principle of 'use or disuse of organs'.
Answer:
The theory of use and disuse of organs says that the morphological characters of organism develop because of specific activities that the organisms perform. If some organ is not used it gets degenerated. If excessively, used, it develops. Thus, the morphological changes take place due to activities or non-working of a particular body parts in an organism.
In simple words: Lamarck's principle of 'use or disuse of organs' suggests that body parts frequently used by an organism develop and strengthen, while those not used weaken and degenerate; these acquired changes are then passed to offspring.

🎯 Exam Tip: Clearly articulate how both 'use' and 'disuse' affect organ development and how this concept formed the basis of Lamarck's evolutionary theory.

 

(b) Give two examples.
Answer:
Due to constant extension of neck to eat foliage from the top of the trees, giraffe's neck became long. Similarly, blacksmith has strong arms due to constant work. Flightless ostrich and emu did not fly and hence their wings became useless. Aquatic birds like swan and duck made their feet suitable for swimming by living in water. Snake lost limbs as it tried burrowing mode.
In simple words: Examples include giraffes developing long necks from stretching, blacksmiths gaining strong arms from work, flightless birds having useless wings due to disuse, and snakes losing limbs by adapting to burrowing.

🎯 Exam Tip: When providing examples, choose clear and well-known illustrations that directly reflect the 'use or disuse' principle, such as the giraffe's neck and a blacksmith's arms.

 

(c) What are acquired characters?
Answer:
Acquired characters are those characters which are obtained during the life time by any organism and passed on to next generations.
In simple words: Acquired characters are traits developed by an organism during its lifetime due to environmental influence or use/disuse, which Lamarck believed could be inherited by offspring.

🎯 Exam Tip: Define acquired characters by emphasizing they are gained during an organism's life and, according to Lamarck, are heritable, though this aspect is now disproven.

 

Write Short Notes

 

Question 1.
Theory of evolution.
Answer:
(1) According to the theory of evolution, first living material was in the form of protoplasm which was formed in ocean.
(2) Gradually, it gave rise to unicellular organisms. Changes took place in these unicellular organisms which made them evolve into larger and more complex organisms.
(3) All evolutionary changes were very slow and gradual taking about 300 crore years to happen.
(4) Different types of organisms were developed as the changes and development that occurred in living organisms was all round and multi-dimensional.
(5) Hence, this overall process of evolution is called organizational and progressive.
(6) Variety of plants and animals developed from the ancestors having different structural and functional organization during the process of evolution.
In simple words: The theory of evolution describes the gradual, slow changes in living organisms over billions of years, starting from simple protoplasm in oceans, evolving into diverse and complex life forms with organizational and progressive development.

🎯 Exam Tip: Summarize the key stages of evolution: origin of protoplasm, unicellular to complex organisms, gradual nature, and resulting diversity of life forms.

 

By Choosing Appropriate Words Given In The Bracket, Complete The Paragraph

 

Question 1.
(translation, anticodon, tRNA, mRNA, amino acids, triplet codon, transcription, DNA)
The .... formed in nucleus comes in cytoplasm. It brings in the coded message from DNA. The message contains the codes for amino acids. The code for each amino acid consists of three nucleotides. It is called as '...........'. Each mRNA is made up of thousands of triplet codons. As per the message on mRNA, are supplied by the . For this purpose, tRNA has '............' having complementary sequence to the codon on mRNA. This is called '...........'.
Answer:
The mRNA formed in nucleus comes in cytoplasm. It brings in the coded message from DNA. The message contains the codes for amino acids. The code for each amino acid consists of three nucleotides. It is called as 'triplet codon'. Each mRNA is made up of thousands of triplet codons. As per the message on mRNA, amino acids are supplied by the tRNA. For this purpose, tRNA has 'anticodon' having complementary sequence to the codon on mRNA. This is called 'translation'.
In simple words: In protein synthesis, mRNA carries the genetic message from the nucleus to the cytoplasm, where tRNA, with its anticodon, brings specific amino acids to the mRNA's triplet codons for protein assembly, a process called translation.

🎯 Exam Tip: Understand the roles of mRNA, tRNA, amino acids, triplet codons, anticodons, and the processes of transcription and translation to fill in the blanks accurately.

 

Question 2.
(Cultural, agriculture, fire, brain, Cro-Magnon, Homo sapiens, Neanderthal)
Evolution of upright man continued in the direction of developing its .......... for the period of about 1 lakh years and meanwhile he discovered the .......... Brain of man, 50 thousand years ago had been sufficiently evolved to the extent that it could be considered as member of the species Neanderthal man can be considered as the first example of wise-man. The man evolved about 50 thousand years ago and afterwards, this evolution had been faster than the earlier. About 10 thousand years ago, wise-man started to practise the ...... It started to rear the cattle-herds and established the cities. ...........development took place later.
Answer:
Evolution of upright man continued in the direction of developing its brain for the period of about 1 lakh years and meanwhile he discovered the fire. Brain of man 50 thousand years ago had been sufficiently evolved to the extent that it could be considered as member of the species Homo sapiens. Neanderthal man can be considered as the first example of wise-man. The Cro-Magnon man evolved about 50 thousand years ago and afterwards, this evolution had been faster than the earlier. About 10 thousand years ago, wise-man started-to practise the agriculture. It started to rear the cattle-herds and established the cities. Cultural development took place later.
In simple words: Human evolution progressed with brain development and the discovery of fire, leading to Homo sapiens and early wise men like Neanderthals and Cro-Magnons. Later, agriculture and city-building marked significant cultural development.

🎯 Exam Tip: Focus on the chronological order of key human evolutionary milestones such as brain development, discovery of fire, appearance of early human species, and the advent of agriculture and culture.

 

Read The Paragraph And Answer The Questions Given Below

 

With the help of RNA, the genes present in the form of DNA participate in the functioning of cell and thereby control the structure and functioning of the body. Information about protein synthesis is stored in the DNA and synthesis of appropriate proteins as per requirement is necessary for body. These proteins are synthesized by DNA through the RNA. This is called 'Central Dogma'. mRNA is produced as per the sequence of nucleotides on DNA. Only one of the two strands of DNA is used in this process. The sequence of nucleotides in mRNA being produced is always complementary to the DNA strand used for synthesis. Besides, there is uracil in RNA instead of thymine of DNA. This process of RNA synthesis is called 'transcription'.

 

Question 1.
Which part of the cell control the structure and functioning of the body?
Answer:
Genes present in the form of DNA along with RNA control the structure and functioning of the body.
In simple words: The genes, which are segments of DNA and work with RNA, are responsible for controlling the cell's structure and all its functions.

🎯 Exam Tip: Identify both DNA (genes) and RNA as the key components responsible for cellular control, as stated in the paragraph.

 

Question 2.
How is a specific protein synthesised in the cell?
Answer:
The information of protein synthesis is stored in the DNA which is utilised as per the requirement of the body. Later the proteins are synthesised by DNA through the RNA.
In simple words: Proteins are synthesized in the cell by using the genetic information stored in DNA, which is then carried out via RNA molecules according to the body's needs.

🎯 Exam Tip: Explain that protein synthesis begins with DNA's information, which is then transcribed and translated with the help of RNA.

 

Question 3.
What is the similarity between mRNA and DNA?
Answer:
The sequence of nucleotides on DNA is copied on mRNA. The nucleotide sequence on mRNA is thus complementary to DNA.
In simple words: The main similarity between mRNA and DNA is that mRNA's nucleotide sequence is a complementary copy of a segment of DNA, reflecting the genetic information.

🎯 Exam Tip: Highlight the complementary nucleotide sequence as the fundamental similarity, explaining that mRNA is a template-based copy of DNA.

 

Question 4.
Give one difference between RNA and DNA.
Answer:
RNA has uracil instead of thymine which is present in DNA.
In simple words: A key difference is that RNA contains the nitrogenous base uracil (U), whereas DNA contains thymine (T) in its place.

🎯 Exam Tip: The most straightforward difference to recall is the presence of uracil in RNA versus thymine in DNA.

 

Question 5.
Define central dogma.
Answer:
Central dogma is the concept that proteins are synthesised by DNA through the RNA.
In simple words: The central dogma is the fundamental concept in molecular biology that describes the flow of genetic information from DNA to RNA to protein synthesis.

🎯 Exam Tip: Define central dogma as the one-way flow of genetic information from DNA to RNA to protein, emphasizing the directional nature of this process.

 

Diagram-Based Questions

 

Question 1.
Observe the figure 1.3 of transcription given on page 9 in this chapter and answer the following questions:

ℹ️ चित्र व्याख्या (Diagram Explanation): यह आरेख प्रतिलेखन की प्रक्रिया को दर्शाता है, जिसमें डीएनए डबल हेलिक्स का एक खंड अनावृत होता है, और इसकी एक स्ट्रैंड mRNA अणु के संश्लेषण के लिए एक टेम्पलेट के रूप में कार्य करती है। आरएनए पोलीमरेज़ आरएनए न्यूक्लियोटाइड (एकल ब्लॉक के रूप में दर्शाया गया) को जोड़कर एक बढ़ती हुई mRNA स्ट्रैंड बनाने की सुविधा प्रदान करता है, जो डीएनए टेम्पलेट के पूरक होती है।
(1) What is the sequence of nucleotides present on one strand of the DNA?
Answer:
ATGCAATT
In simple words: Based on the diagram, the sequence of nucleotides on the DNA strand acting as the template is ATGCAATT.

🎯 Exam Tip: Carefully read the nucleotide sequence shown on the DNA template strand in the diagram to ensure accuracy.

 

(2) According to the above sequence on DNA, what will be the transcribed sequence on the mRNA molecule?
Answer:
UACGUUAA
In simple words: For the given DNA sequence ATGCAATT, the transcribed mRNA sequence will be UACGUUAA, with Uracil replacing Thymine.

🎯 Exam Tip: Remember the base pairing rules for transcription: A with U (in RNA), T with A, G with C, and C with G.

 

(3) Which enzyme is taking part in the above process of transcription?
Answer:
RNA polymerase takes part in the process of transcription.
In simple words: The enzyme responsible for synthesizing mRNA from a DNA template during transcription is RNA polymerase.

🎯 Exam Tip: Identify RNA polymerase as the crucial enzyme that catalyzes the synthesis of RNA from a DNA template.

 

Question 2.
Observe the figure 1.5 of translation and translocation, given on page 9 this chapter and answer the following questions:

ℹ️ चित्र व्याख्या (Diagram Explanation): यह आरेख एक राइबोसोम के भीतर होने वाली अनुवाद और स्थानांतरण की प्रक्रियाओं को दर्शाता है। यह एक mRNA स्ट्रैंड को राइबोसोम द्वारा पढ़े जाने को दिखाता है, जिसमें tRNA अणु (विशिष्ट अमीनो एसिड ले जाने वाले) mRNA पर पूरक कोडन से जुड़ते हैं। राइबोसोम फिर mRNA के साथ चलता है, जिससे एक पॉलीपेप्टाइड श्रृंखला का निर्माण होता है।
(1) Which is the initiation codon? Where is it present?
Answer:
AUG is the initiation codon, which is present on the mRNA.
In simple words: The initiation codon is AUG, located on the mRNA molecule, and it signals the start of protein synthesis.

🎯 Exam Tip: Recognize AUG as the universal start codon for translation and specify its location on the mRNA molecule.

 

(2) What are the types of RNA present inside the ribosome? Which triplet codon is present on it?
Answer:
There are two molecules of tRNA present inside the ribosome. The triplet codons present on them are UAC and AAG respectively.
In simple words: Inside the ribosome, two tRNA molecules are present, carrying the anticodon triplets UAC and AAG, which are complementary to mRNA codons.

🎯 Exam Tip: Identify tRNA as the type of RNA bringing amino acids to the ribosome, and accurately state the anticodon sequences shown in the diagram.

 

(3) Which genetic code is present on mRNA that is leaving the nucleus? What must be the sequence on the DNA to have such code on mRNA?
Answer:
The mRNA that leaves the nucleus has genetic code: A UGUUCAAA
The genetic code on DNA therefore should be as follows: TACAAGTTT
In simple words: If the mRNA code leaving the nucleus is AUGUUCAAA, then the complementary DNA template sequence from which it was transcribed must be TACAAGTTT.

🎯 Exam Tip: To convert mRNA to DNA, remember that Uracil (U) in mRNA corresponds to Adenine (A) in DNA, and Adenine (A) in mRNA corresponds to Thymine (T) in DNA, while G and C remain complementary.

 

Question 3.
Observe the figure 1.6 given on page 10 from this chapter. Answer the following question based on your observations:

ℹ️ चित्र व्याख्या (Diagram Explanation): यह आरेख एक उत्परिवर्तन घटना को दर्शाता है, जिसमें डीएनए न्यूक्लियोटाइड की "मुख्य अनुक्रम" (जैसे TGC) और एक "प्रतिस्थापन" दिखाया गया है जहाँ एक न्यूक्लियोटाइड (G) को दूसरे (A) से प्रतिस्थापित किया जाता है, अनुक्रम को TAT में बदल दिया जाता है (उत्तर स्पष्टीकरण के आधार पर GAT भी)। यह एक बिंदु उत्परिवर्तन को दर्शाता है जहाँ एक आधार युग्म बदल जाता है, जिससे आनुवंशिक कोड में परिवर्तन होता है।
What is the significance of this figure from the viewpoint of evolution? Explain in brief.
Answer:
In the figure, the process of mutation is shown. The original nucleotide sequence of TGC is replaced by new mutated sequence GAT. The change in the nucleotide sequence will change the DNA.
This will result in the change in genes and then changing the hereditary characters. Due to such change in genes, the evolution proceeds. The mutation so formed can be minor or major. The greater the impact of the change, the evolution takes place rapidly. The mutation thereby produce recombinations leading to diversity.
In simple words: This figure demonstrates mutation, a change in DNA sequence that alters genes and hereditary characters. Mutations, whether minor or major, drive evolution by creating new genetic variations and recombinations, leading to diversity in species.

🎯 Exam Tip: Explain that mutations are the source of new genetic variation, which natural selection can then act upon, thus fueling evolutionary change and diversity.

 

Question 4.
Observe the picture and answer the following questions:

ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र विभिन्न कशेरुक प्रजातियों में भ्रूण विकास के चरणों की एक श्रृंखला को प्रदर्शित करता है, जिन्हें उनके प्रारंभिक चरणों में समानताओं को उजागर करने के लिए व्यवस्थित किया गया है। मछली, सैलामैंडर, कछुए, चूजे और मानव भ्रूण जैसे विभिन्न जानवरों को दर्शाने वाले ये चित्र, उनके प्रारंभिक विकास में उल्लेखनीय रूप से समान प्रतीत होते हैं, जो एक सामान्य विकासवादी वंश की अवधारणा का समर्थन करते हैं।
(1) Which evidence of evolution is shown in the picture?
Answer:
Embryological evidences of evolution are shown in this picture.
In simple words: The picture illustrates embryological evidences, which are similarities in the early embryonic development of different species, suggesting a common ancestry.

🎯 Exam Tip: Correctly identify embryological evidence as the concept depicted, focusing on the shared developmental patterns.

 

(2) What can be proven with this proof?
Answer:
The similarities in the initial embryonic stages of different vertebrates shows that there was a common origin of all of them. Thus embryological evidences prove that there was common vertebrate ancestor.
In simple words: This evidence demonstrates that early embryonic similarities among vertebrates suggest they all evolved from a common ancestor, supporting the idea of shared evolutionary origin.

🎯 Exam Tip: Emphasize that shared embryonic features indicate a common evolutionary lineage among different vertebrate species.

 

(3) Give one more example of evidence of evolution.
Answer:
Palaeontological evidences such as vestigial organs and connecting links are another examples of evolutionary evidences.
In simple words: Besides embryology, other significant evidences for evolution include fossils (palaeontological evidence), vestigial organs, and connecting links.

🎯 Exam Tip: Be ready to name other types of evolutionary evidence like palaeontological (fossils), anatomical, and morphological evidences, or vestigial organs and connecting links.

 

Question 5.
Which concept/theory do you remember after seeing this picture of Giraffes? Describe it in brief.

ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र लगातार लंबी गर्दन वाले जिराफों की एक श्रृंखला को दर्शाता है। इस दृश्य प्रस्तुति का उपयोग आमतौर पर लैमार्क के "उपार्जित लक्षणों के वंशानुक्रम" के सिद्धांत को समझाने के लिए किया जाता है, यह सुझाव देते हुए कि जिराफों ने उच्च पत्तियों तक पहुँचने के लिए लगातार गर्दन को खींचकर पीढ़ियों से लंबी गर्दन विकसित की, और ये उपार्जित लक्षण फिर उनकी संतानों में पारित हो गए।
Answer:
(1) The picture is based on the Lamarck's principle of 'use and disuse of organs'.
(2) The morphological characters of organism develop because of specific activities that the organisms perform.
(3) If some organ is not used it gets degenerated. If excessively used, it develops further.
(4) Thus, the morphological changes take place due to activities or non-working of a particular body parts in an organism. Due to constant extension of neck to eat foliage from the top of the trees, giraffe's neck became long.
In simple words: The image of giraffes with long necks relates to Lamarck's theory of 'use and disuse,' where organs that are frequently used (like a giraffe's neck stretching for leaves) develop, while unused ones degenerate, and these acquired traits are passed on.

🎯 Exam Tip: Clearly link the giraffe example to Lamarck's theory, explaining how the repeated 'use' of the neck for reaching food was thought to lead to its elongation and inheritance.

 

Activity-Based Questions

 

Try This (Text Book Page No. 4)

ℹ️ चित्र व्याख्या (Diagram Explanation): यह छवि विभिन्न जानवरों के चेहरों (एक कुत्ता, एक भेड़, एक लोमड़ी) और विभिन्न पौधों के पत्तों/फलों (संभवतः विभिन्न फलों के प्रकार और पत्ती के शिरा विन्यास पैटर्न का प्रतिनिधित्व करने के लिए) को प्रदर्शित करती है। इसका उद्देश्य बाहरी विशेषताओं की तुलना करके समानताओं और अंतरों को खोजने के लिए, रूपात्मक प्रमाणों को चित्रित करना है, जिससे एक सामान्य वंश का संकेत मिलता है।
Observe the above images and note the similarities between given animal images and plant images.
Answer:
The above pictures of the animals show similarities such as structure of mouth, position of eyes, structure of nostrils and ear pinnae and body fur. In pictures of plants there are similarities in characters like leaf shape, leaf venation, leaf petiole, etc. These above morphological evidences show that there may be a common ancestor for all of the species shown.
In simple words: The observed similarities in animal features (e.g., mouth, eye position) and plant traits (e.g., leaf shape, venation) across different species serve as morphological evidence, suggesting a shared evolutionary ancestry.

🎯 Exam Tip: When analyzing morphological evidence, focus on common structural plans, even if functions differ, as these suggest shared evolutionary origins.

 

Observe And Discuss

 

Question 1.
Observe the pictures given below. (Text Book Page No. 5)

ℹ️ चित्र व्याख्या (Diagram Explanation): यह छवि कई जीवाश्म अवशेषों को दर्शाती है, जिसमें एक डायनासोर का कंकाल और चट्टानों में जमे हुए छोटे जीवाश्म जीव, संभवतः मछली या कीड़े शामिल हैं। ये जीवाश्म विकास के लिए पुरातात्विक प्रमाण के रूप में काम करते हैं, जो प्राचीन जीवन रूपों के अस्तित्व को प्रदर्शित करते हैं और उनकी संरचना तथा उनके निवास के भूवैज्ञानिक समय अवधियों में अंतर्दृष्टि प्रदान करते हैं।
Answer:
(1) Fossils offer palaeontological evidence for the evolutionary process.
(2) Due to some natural calamities the organisms get buried during ancient times.
(3) The impressions and remnants of such organisms remain preserved underground. The hot lava also traps some organisms or their impressions. All such formations form fossils.
(4) Study of fossils help the researcher to understand the characteristics of the organisms that existed in the.past.
(5) Carbon dating method also helps in finding out exact age of the fossil. According to the structure of earth's crust the fossils are obtained at specific depths.
(6) The oldest ones are obtained at the depth while the relatively recent ones occupy the upper surface. Thus fossils of invertebrates were seen in very old Palaeozoic era. Later were seen fossils of Pisces, Amphibia and Reptilia. The Mesozoic era was dominated by reptiles while Coenozoic era showed presence of mammals.
(7) In this way, study of fossils unfold the evolutionary secrets.
In simple words: Fossils provide palaeontological evidence of evolution, as they are preserved remnants of ancient organisms. Their study, aided by carbon dating, reveals past life forms, their characteristics, and their chronological appearance in geological layers, thereby unveiling evolutionary history.

🎯 Exam Tip: Focus on how fossil records, along with carbon dating, provide a chronological history of life, illustrating the progression from simpler to more complex forms over geological time.

 

Question 2.
Observe the pictures given and discuss the characters observed. (Text Book Page No. 6)

ℹ️ चित्र व्याख्या (Diagram Explanation): यह छवि तीन जानवरों को दिखाती है: एक डकबिल प्लैटिपस, एक लंगफिश और एक पेरिपेटस। इन जानवरों को "कनेक्टिंग लिंक" के रूप में प्रस्तुत किया गया है, जो विभिन्न प्रमुख पशु समूहों के बीच संक्रमणकालीन विशेषताओं को प्रदर्शित करते हैं। उदाहरण के लिए, डकबिल प्लैटिपस सरीसृप (अंडा देना) और स्तनधारी (स्तन ग्रंथियां, बालों वाली त्वचा) दोनों लक्षण दिखाता है, जो विकासवादी मार्गों को दर्शाता है।
Answer:
Some living organisms possess some characters in them which are the distinctive features of different groups or phyla. Such individuals connect these two groups by sharing the characters of both and hence they are known as connective links.
Examples:
(1) Peripatus: Peripatus is the connecting link between Annelida and Arthropoda. It shows characters of both animal phyla. Like annelid worm, it shows segmented body, thin cuticle and parapodia. Like an arthropod, it shows open circulatory system and tracheal system for respiration.
(2) Duck Billed platypus: This is a connecting link between reptiles and mammals. Like reptiles it lays eggs but like mammals it has mammary glands and hairy skin.
(3) Lung fish: Lung fish is a connecting link between fishes and amphibians. Though a fish, it shows lungs for respiration as in amphibian animals.
(4) Connecting links indicate the direction and hierarchy of evolution.
In simple words: Connecting links are organisms that exhibit traits of two different taxonomic groups, serving as evolutionary bridges. Examples like Peripatus (Annelida and Arthropoda), Duck-billed platypus (reptiles and mammals), and Lungfish (fishes and amphibians) demonstrate evolutionary pathways and relationships.

🎯 Exam Tip: For connecting links, clearly define them as organisms with characteristics of two different groups and provide specific examples, detailing the shared traits for each.

 

Project 1. Internet is my friend: Collect the information from the internet about Big-Bang theory related with the formation of stars and planets and present it in your class.

 

Project 2. Use of ICT: Collect the information of geological dating and present it in the classroom.

 

Project 3. Use of ICT: Find how the vestigial organs in certain animals are functional in others. Present the information in your class and send it to others.

 

Project 4. Internet is my friend: Collect the pictures and information of various species of monkeys from internet.

 

Class 10 Questions And Answers

 

10th Std Science Part 2 Questions And Answers:

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