Grade 10 Q&A: Chapter 11: Heredity and Evolution

Concept Questions

Q1: What is heredity?

Answer: Heredity is the transmission of biological characters from one generation to another, i.e., from parents to their offspring.

Q2: What is the full form of DNA?

Answer: The full form of DNA is Deoxyribonucleic Acid.

Q3: What is the full form of RNA?

Answer: The full form of RNA is Ribonucleic Acid.

Q4: What is the 'Central Dogma of Molecular Biology'?

Answer: The Central Dogma of Molecular Biology states that genetic information flows from DNA to RNA to protein. This means DNA synthesizes RNA (transcription), and RNA synthesizes protein (translation).

Q5: Define 'transcription'.

Answer: Transcription is the process of synthesizing an RNA molecule from a DNA template. In this process, the sequence of nucleotides in a gene is copied into a complementary RNA sequence.

Q6: Define 'translation'.

Answer: Translation is the process by which the genetic information carried by messenger RNA (mRNA) is decoded to synthesize proteins. This process occurs on ribosomes.

Q7: What is 'translocation' in protein synthesis?

Answer: Translocation in protein synthesis is the movement of the ribosome along the mRNA molecule by one codon at a time during translation, allowing the next tRNA to bind and the polypeptide chain to elongate.

Q8: What is a 'mutation'?

Answer: A mutation is a sudden, heritable change in the genetic material (DNA or RNA) of an organism. It can involve changes in a single gene (gene mutation) or in the structure or number of chromosomes (chromosomal mutation).

Q9: What is 'evolution'?

Answer: Evolution is the gradual change occurring in living organisms over a long duration. It is the process by which different kinds of living organisms are thought to have developed and diversified from earlier forms during the history of the Earth.

Q10: Name two types of evidence for evolution.

Answer: Two types of evidence for evolution are morphological evidence and anatomical evidence.

Q11: What are 'vestigial organs'?

Answer: Vestigial organs are rudimentary or underdeveloped organs in an organism that were functional in its ancestors but have lost their original function over evolutionary time due to changes in lifestyle or environment (e.g., appendix in humans, wisdom teeth).

Q12: Who proposed the 'Theory of Natural Selection'?

Answer: Charles Darwin proposed the 'Theory of Natural Selection'.

Q13: What is 'Lamarckism'?

Answer: Lamarckism is a theory of evolution proposed by Jean-Baptiste Lamarck, which suggests that organisms can acquire characteristics during their lifetime through use or disuse and then pass these acquired traits on to their offspring.

Q14: Define 'speciation'.

Answer: Speciation is the evolutionary process by which new biological species arise. It involves the divergence of a single evolutionary lineage into two or more genetically independent lineages.

Application-Based Questions

Q15: Explain how the sequence of nucleotides on DNA determines the sequence of amino acids in a protein.

Answer: The sequence of nucleotides on DNA determines the sequence of amino acids in a protein through a genetic code. During transcription, the DNA sequence is copied into an mRNA molecule. Then, during translation, each set of three consecutive nucleotides on the mRNA (called a codon) specifies a particular amino acid. Transfer RNA (tRNA) molecules, each carrying a specific amino acid, recognize these codons, ensuring that amino acids are linked in the correct order to form the protein.

Q16: How do 'connecting links' provide evidence for evolution? Give an example.

Answer: Connecting links are organisms that exhibit characteristics of two different groups of organisms, suggesting an evolutionary link or transition between them. They provide strong evidence for evolution by showing intermediate stages in the development of species. For example, the duck-billed platypus is a connecting link between reptiles and mammals, as it lays eggs (like reptiles) but has mammary glands and hair (like mammals).

Q17: Describe how 'embryological evidence' supports the theory of evolution.

Answer: Embryological evidence for evolution comes from comparing the embryonic development of different organisms. It shows that embryos of different vertebrates (e.g., fish, amphibians, reptiles, birds, mammals) exhibit striking similarities in their early developmental stages, such as the presence of gill slits and a tail, even if these features disappear later in development. This suggests a common ancestry and shared evolutionary history.

Q18: Explain Darwin's concept of 'survival of the fittest' in the context of natural selection.

Answer: In Darwin's theory of natural selection, 'survival of the fittest' refers to the idea that individuals with traits best suited to their environment are more likely to survive, reproduce, and pass on those advantageous traits to their offspring. Over generations, this leads to the accumulation of beneficial traits in a population, driving evolutionary change.

Q19: How do 'anatomical evidence' and 'morphological evidence' differ in supporting evolution?

Answer: * Anatomical Evidence: Compares the internal structures of different organisms. Homologous organs (e.g., forelimbs of humans, cats, whales, bats) have similar basic structures but different functions, indicating a common ancestor. * Morphological Evidence: Compares the external features and structures of different organisms. Similarities in external characteristics (e.g., leaf venation patterns in plants, body plans of animals) suggest common ancestry, even if their functions might vary slightly.

Higher-Order Thinking Questions

Q20: Discuss the implications of mutations for both evolution and genetic disorders.

Answer: Mutations are the ultimate source of all genetic variation, which is the raw material for evolution. Beneficial mutations can lead to new traits that improve an organism's survival and reproduction, driving adaptation and speciation. However, most mutations are neutral or harmful. Harmful mutations can disrupt gene function, leading to genetic disorders (e.g., sickle cell anemia, cystic fibrosis). Thus, mutations are a double-edged sword: essential for evolutionary change but also a cause of genetic diseases.

Q21: "Human evolution is a continuous process." Justify this statement with examples.

Answer: Human evolution is indeed a continuous process, though often subtle and slow compared to our lifespan. While major anatomical changes are less common today, evolution continues at the genetic level. Examples include: 1. Lactose Tolerance: The ability to digest lactose into adulthood has evolved independently in several human populations that traditionally domesticated dairy animals. 2. Disease Resistance: Populations exposed to certain diseases (e.g., malaria) have evolved genetic resistances (e.g., sickle cell trait). 3. Altitude Adaptation: Populations living at high altitudes (e.g., Tibetans) have evolved unique physiological adaptations for coping with low oxygen levels. These ongoing adaptations demonstrate that natural selection continues to act on human populations in response to environmental and cultural pressures.

Q22: Compare and contrast Darwin's Theory of Natural Selection with Lamarckism.

Answer: Darwin's Theory of Natural Selection: * Variation exists naturally within a population. * Individuals with advantageous variations are more likely to survive and reproduce (survival of the fittest). * These advantageous traits are inherited by offspring. * Evolution occurs through the accumulation of favorable variations over generations. * Changes are random, and the environment selects the best-adapted individuals. Lamarckism (Theory of Inheritance of Acquired Characters): * Organisms develop new characteristics during their lifetime in response to environmental needs (e.g., giraffe's neck stretching to reach leaves). * These acquired characteristics are then passed on to their offspring. * Changes are directed by the organism's will or need. Contrast: Darwin believed in inherited variations being selected, while Lamarck believed in acquired traits being inherited. Darwin's theory is widely accepted; Lamarck's is largely disproven (e.g., a bodybuilder's muscles are not inherited by their children).

Q23: How does the process of 'protein synthesis' (transcription and translation) ensure the accurate expression of genetic information?

Answer: Protein synthesis ensures accurate genetic expression through a highly regulated two-step process: 1. Transcription: DNA's genetic information is precisely copied into mRNA. RNA polymerase ensures that base pairing rules are followed (A with U, T with A, C with G), creating a complementary mRNA strand. This ensures the correct genetic message is carried from the nucleus to the ribosomes. 2. Translation: The mRNA sequence is read in codons (three-nucleotide units). Each codon specifies a particular amino acid. tRNA molecules, with their specific anticodons, ensure that the correct amino acid is brought to the ribosome for each codon. The ribosome then catalyzes the formation of peptide bonds between amino acids, building the protein in the exact sequence dictated by the mRNA, thus accurately translating the genetic code into a functional protein.

Q24: Discuss the significance of 'paleontological evidence' (fossils) in understanding evolution.

Answer: Paleontological evidence, primarily in the form of fossils, is immensely significant in understanding evolution because: 1. Direct Evidence of Past Life: Fossils are the preserved remains or traces of organisms from the past, providing direct proof that life on Earth has changed over geological time. 2. Transitional Forms: Fossils often reveal transitional forms that show intermediate stages between different groups of organisms (e.g., *Archaeopteryx* showing features of both reptiles and birds), supporting the idea of common ancestry. 3. Dating and Chronology: The geological layers in which fossils are found allow scientists to date them and establish a chronological order of life forms, demonstrating the progression of evolution. 4. Extinction Events: The fossil record also reveals mass extinction events, which have shaped the course of evolution by removing dominant species and opening up ecological niches for new forms to diversify.

Q25: How can the study of human evolution help us understand current human health and societal challenges?

Answer: The study of human evolution provides crucial insights into current human health and societal challenges: 1. Disease Susceptibility: Understanding our evolutionary past helps explain why we are susceptible to certain diseases (e.g., obesity, diabetes, back pain) that were less prevalent in ancestral environments. Our bodies are adapted to a different lifestyle than modern sedentary, high-sugar diets. 2. Genetic Disorders: Evolutionary genetics helps trace the origins and spread of genetic disorders within populations. 3. Behavioral Patterns: Insights into our social and cognitive evolution can shed light on modern human behaviors, cooperation, and conflict. 4. Adaptation to Environment: It explains adaptations to diverse environments (e.g., skin color variation, altitude tolerance) and how these might interact with modern environmental changes. By understanding our evolutionary history, we can better address contemporary health issues, design more effective public health strategies, and even inform our understanding of human behavior and societal structures.

Q26: Describe the process of 'gene mutation' and its potential effects on an organism.

Answer: A gene mutation is a change in the nucleotide sequence of a gene. It can occur due to errors during DNA replication or exposure to mutagens (e.g., radiation, certain chemicals). Potential effects on an organism: 1. No Effect (Silent Mutation): If the mutation does not change the amino acid sequence, it might have no observable effect. 2. Beneficial Effect: Rarely, a mutation can introduce a new trait that provides an advantage, leading to natural selection and evolution. 3. Harmful Effect: Most mutations are harmful. They can lead to: * Non-functional Proteins: If the mutation alters the amino acid sequence significantly, the resulting protein might not function correctly. * Genetic Disorders: Many inherited diseases (e.g., cystic fibrosis, Huntington's disease) are caused by specific gene mutations. * Cancer: Mutations in genes that control cell growth and division can lead to uncontrolled cell proliferation and tumor formation. The effects depend on where the mutation occurs in the gene, the type of change, and its impact on protein function.

Q27: How does the concept of 'common ancestry' underpin all the evidence for evolution?

Answer: The concept of 'common ancestry' is the central tenet underpinning all evidence for evolution. It posits that all life on Earth shares a common ancestor, and the diversity of life we see today has arisen through gradual divergence from this ancestor over vast periods. * Homologous structures (anatomical evidence): Similar bone structures in different species (e.g., vertebrate forelimbs) are best explained by inheritance from a common ancestor, which then diversified. * Embryological similarities: The striking resemblances in early embryonic development across diverse species suggest a shared developmental program inherited from a common ancestor. * Molecular similarities (DNA/protein): The universal genetic code and similarities in DNA and protein sequences among different organisms strongly indicate a common origin. The more closely related species are, the more similar their molecular sequences. * Fossil record: The discovery of transitional fossils and the chronological appearance of different life forms in the rock layers support the idea of gradual change and descent from common ancestors. Without the concept of common ancestry, these diverse lines of evidence would appear as unrelated coincidences rather than compelling support for a unified theory of life's history.

Q28: What is the significance of the universal genetic code in understanding heredity and evolution?

Answer: The universal genetic code is profoundly significant because it means that almost all living organisms use the same set of codons (three-nucleotide sequences) to specify the same amino acids during protein synthesis. 1. Evidence for Common Ancestry: This universality is one of the strongest pieces of evidence for common ancestry, suggesting that all life on Earth evolved from a single primordial ancestor that established this code. 2. Interchangeability of Genes: It allows for genetic engineering, where genes from one organism can be inserted into another, and the recipient organism can still produce the corresponding protein. 3. Understanding Heredity: It provides the fundamental mechanism by which genetic information is reliably passed down and expressed across generations, explaining how traits are inherited. 4. Predicting Protein Sequences: Knowing the genetic code allows scientists to predict the amino acid sequence of a protein from a DNA or RNA sequence, which is crucial for genetic research and biotechnology.

Q29: How do 'gene flow' and 'genetic drift' contribute to changes in allele frequencies in a population, leading to evolution?

Answer: Both gene flow and genetic drift are mechanisms that cause changes in allele frequencies within a population, contributing to evolution: 1. Gene Flow: This is the transfer of genetic material (alleles) from one population to another, typically through migration and interbreeding. Gene flow tends to reduce genetic differences between populations, making them more similar, and can introduce new alleles into a population, increasing its genetic variation. 2. Genetic Drift: This is the change in the frequency of an existing gene variant (allele) in a population due to random sampling of organisms. It is particularly significant in small populations, where random events (like a natural disaster, or simply which individuals happen to reproduce) can have a disproportionately large effect on allele frequencies, leading to loss of genetic variation or fixation of certain alleles, regardless of their adaptive value. Both processes, along with mutation and natural selection, are key drivers of evolutionary change, shaping the genetic makeup of populations over time.

References

1. MSBSHSE Class 10 Science and Technology Textbook Part 2 (2021-22 English) - Chapter 1: Heredity and Evolution
2. Maharashtra State Board 10th Standard Science Syllabus 2025-26
3. Balbharati Science and Technology Part 2 Textbook
4. Shaalaa.com Balbharati solutions for Science and Technology 2