Heredity and Evolution — Maharashtra (SSC) Class 10 Science Solutions (Free)
Free step-by-step Maharashtra (SSC) Class 10 Science solutions for "Heredity and Evolution" — important questions with detailed answers, download PDF for board exam preparation.
TL;DR: Free step-by-step Maharashtra (SSC) Class 10 Science solutions for "Heredity and Evolution" — important questions with detailed answers, download PDF…
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Q1: State Mendel's laws of inheritance: law of segregation and law of independent assortment.
Law of segregation: allele pairs separate during gamete formation; each gamete receives one allele. During fertilization, allele pairs reunite in offspring. Law of independent assortment: alleles of different genes assort independently during gamete formation. Example: in a dihybrid cross (AaBb × AaBb), offspring ratio is 9:3:3:1. These laws explain how traits pass from parents to offspring through generations.
Q2: Explain dominance and recessiveness in Mendelian genetics with an example.
Dominant allele (A) masks the effect of recessive allele (a). Dominant phenotype appears in AA and Aa genotypes. Recessive phenotype only appears in aa. Example: in pea plants, seed color is dominant (yellow) over recessive (green). Cross: AA (yellow) × aa (green) produces Aa (all yellow F1). F1 × F1 gives 3 yellow : 1 green ratio, revealing hidden recessive allele in F2.
Q3: What is evolution? Explain Darwin's theory of natural selection with evidence.
Evolution is the change in allele frequencies in populations over time, leading to speciation. Darwin's natural selection: variation exists in populations; organisms compete for resources; those with beneficial traits survive and reproduce more, passing advantageous genes. Evidence: fossil records show gradual changes; homologous structures (bat wing, human arm, whale flipper) indicate common ancestor; bacteria develop antibiotic resistance; peppered moth color change in industrial England.
Q4: Define speciation and explain allopatric and peripatric speciation mechanisms.
Speciation is the evolutionary process forming new species from existing ones when populations can no longer interbreed. Allopatric speciation: geographic isolation (mountain, river) prevents gene flow; populations diverge genetically, accumulate differences, become reproductively isolated. Example: Darwin finches on different Galápagos islands. Peripatric speciation: small founding population (bottleneck) in new location; genetic drift and adaptation drive rapid speciation. Both require reprodu…
Q5: Explain genetic drift and gene flow, their effects on allele frequencies in small populations.
Genetic drift: random changes in allele frequencies in small populations; sampling error causes alleles to be lost or fixed. Example: founder effect when colonists carry only subset of parental population's alleles. Gene flow: movement of alleles between populations via migration, increasing genetic diversity. Small populations are vulnerable to drift; migration restores lost alleles. Together they shape evolution at population level; drift is stronger in small populations.
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