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Unit-10 Evolution
Answer: Molecular biology compares DNA and protein sequences; the degree of similarity reveals how closely organisms are related.
Answer: In biology, fitness means the ability to survive and reproduce in a particular environment, not physical strength.
Answer: Members of the same species share the greatest genetic similarity because they are the most closely related.
Answer: Natural selection requires variation; if all individuals are identical, selection cannot favour one over another.
Answer: Mutations are random changes in DNA that introduce new variations upon which natural selection can act.
Answer: Bacteria with genes for resistance survive antibiotic treatment and multiply, so resistant strains become common.
Answer: Fossils provide direct physical evidence that organisms lived in the past and changed over time.
Answer: Natural selection acts on existing variations, so variation is essential for evolution to occur.
Answer: Without favourable variations, individuals are less suited to their environment and more likely to die before they can reproduce.
Answer: Natural selection favours individuals with traits that improve survival and reproduction in their environment.
Answer: Producing more offspring than resources can support leads to competition among individuals.
Answer: According to the principle of superposition, deeper layers of rock contain older fossils.
Answer: Choosing high-milk-yield cows for breeding is artificial selection by humans.
Answer: DNA comparisons show that chimpanzees share the greatest genetic similarity with humans among living species.
Answer: Evolution is a gradual process that typically occurs over millions of years across countless generations.
Answer: Natural selection operates on individual organisms through their survival and reproductive success.
Answer: An adaptation is any inherited trait that improves an organism's chance of survival and reproduction.
Answer: Isolation plus accumulated variation allows a population to evolve separately until it becomes a distinct species.
Answer: The shared skeletal plan of mammalian forelimbs indicates that these species evolved from a common ancestor, a case of homology.
Answer: Shared genes and similar DNA sequences across species are molecular evidence of common descent.