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Variation refers to the differences in characteristics among individuals of the same species. It plays a crucial role in evolution, as it provides the raw material for natural selection to act upon. Variations arise due to differences in genetic composition, environmental influences, and interactions between genes and the environment. Sources of Variation: Genetic Mutations: These … Read more
Evolution: The gradual change in species over time due to genetic variation and natural selection. Homologous organs: Structures that have a similar basic design but different functions, indicating a common ancestry. Speciation: The process by which new species evolve from existing ones due to genetic differences and reproductive isolation. Natural selection: A process where organisms … Read more
a. Which variety was more common when there was more air pollution? Give a reason. The dark-colored (melanic) variety was more common when air pollution increased because soot-covered trees made it easier for dark moths to camouflage and avoid predators. b. Which variety is more common in England nowadays? Give a reason. The light-colored variety … Read more
Palaeontology is the study of fossils, which are preserved remains or traces of ancient life. Fossils provide direct evidence of how organisms have changed over millions of years. Types of Fossil Evidence: Transitional Fossils: These show intermediate forms between ancient and modern species. Example: Archaeopteryx, which had both reptilian (teeth, claws) and avian (feathers, wings) … Read more
Selective breeding, also known as artificial selection, is a process in which humans breed organisms to enhance specific traits. Unlike natural selection, where nature determines which traits are advantageous, in selective breeding, humans choose desirable characteristics. Examples of Selective Breeding: Agriculture: Farmers have bred wheat for higher yield and disease resistance. Livestock: Dairy cows have … Read more
Genetic mutations are sudden changes in the DNA sequence that create new genetic variations within a species. They can occur due to errors during DNA replication, exposure to radiation, chemicals, or viruses. Types of Mutations: Beneficial Mutations: These provide an advantage, such as antibiotic resistance in bacteria. Neutral Mutations: These do not affect survival, such … Read more
Comparative embryology shows that embryos of different species share common developmental stages, suggesting a common ancestor. For example, human and fish embryos have gill slits in early development, indicating shared ancestry. Related Questions: Explain the homologous structures in plants. Why was the theory of evolution attributed to Darwin? What is meant by descent with modification? … Read more
Convergent evolution occurs when unrelated species develop similar traits due to adapting to similar environments. An example is the streamlined body shape of sharks (fish) and dolphins (mammals), which evolved separately for efficient swimming. Related Questions: Explain the homologous structures in plants. Why was the theory of evolution attributed to Darwin? What is meant by … Read more
Fossils provide a historical record of life on Earth, showing how species have changed over time. They help scientists identify transitional forms, such as Archaeopteryx, which links reptiles and birds. Related Questions: Explain the homologous structures in plants. Why was the theory of evolution attributed to Darwin? What is meant by descent with modification? Differentiate … Read more
Industrial melanism refers to the evolutionary process in which darker-colored organisms become more common in industrial areas due to pollution. A classic example is the peppered moth, which evolved darker coloration to blend with soot-covered trees. Related Questions: Explain the homologous structures in plants. Why was the theory of evolution attributed to Darwin? What is … Read more