1. What is Lamarck’s theory of evolution? Explain its key principles.
Answer:
Lamarck’s theory of evolution, known as Lamarckism, was proposed by Jean-Baptiste Lamarck. The key principles include:
- Use and Disuse: Organs that are frequently used become stronger and larger, while those that are not used diminish over time.
- Inheritance of Acquired Traits: Traits acquired during an organism’s lifetime can be passed to its offspring.
- Tendency Toward Perfection: Organisms have an inherent tendency to adapt and progress toward perfection.
For example, Lamarck suggested that giraffes developed long necks because their ancestors stretched their necks to reach high branches, and this trait was passed to future generations.
2. What is Darwin’s theory of evolution? Discuss its fundamental aspects.
Answer:
Darwin’s theory of evolution, known as Darwinism, is based on the concept of natural selection. Its fundamental aspects include:
- Variation: Individuals in a population exhibit variations in traits.
- Struggle for Existence: Organisms compete for limited resources.
- Survival of the Fittest: Individuals with advantageous traits are more likely to survive and reproduce.
- Inheritance: Beneficial traits are passed to offspring.
- Gradual Change: Over generations, natural selection leads to evolution and the emergence of new species.
Darwin observed these principles during his studies of finches in the Galápagos Islands.
3. How do Lamarck and Darwin differ in explaining the mechanism of evolution?
Answer:
Lamarck and Darwin proposed contrasting mechanisms of evolution:
- Lamarck: Believed that evolution occurs through the inheritance of acquired traits. For instance, an organism can develop a trait during its lifetime (like a longer neck) and pass it to offspring.
- Darwin: Suggested that evolution is driven by natural selection. Traits beneficial for survival and reproduction are naturally selected over generations. Variations occur randomly, not through use or disuse.
4. What are the criticisms of Lamarck’s theory of evolution?
Answer:
Criticisms of Lamarck’s theory include:
- Lack of Genetic Evidence: Modern genetics shows that acquired traits are not inherited because they do not alter the genetic material.
- Experiments Contradicting Lamarckism: For example, cutting tails off mice for generations does not result in tailless offspring.
- Overemphasis on Individual Effort: Evolution occurs at the population level, not through the efforts of individual organisms.
5. What role does natural selection play in Darwin’s theory?
Answer:
Natural selection is the cornerstone of Darwin’s theory. It ensures that:
- Individuals with advantageous traits are more likely to survive and reproduce.
- Over time, these traits become more common in the population.
- Unfavorable traits are gradually eliminated.
This process leads to the adaptation of organisms to their environment and the formation of new species.
6. Explain the concept of “use and disuse” in Lamarckism with an example.
Answer:
The concept of “use and disuse” in Lamarckism states that organs or traits that are frequently used become stronger and more developed, while those that are not used weaken and may disappear.
Example: According to Lamarck, giraffes developed long necks because their ancestors stretched to reach higher leaves. The continued use of neck muscles and bones led to the elongation of the neck over generations.
7. How did Darwin’s observations in the Galápagos Islands contribute to his theory?
Answer:
Darwin observed variations in the beaks of finches on different islands of the Galápagos. These variations corresponded to the type of food available on each island. He concluded that:
- Variations arise naturally in populations.
- Birds with beak shapes suited to their food source were more likely to survive and reproduce.
This supported his idea of natural selection and adaptation.
8. What evidence supports Darwin’s theory of natural selection?
Answer:
Evidence supporting Darwin’s theory includes:
- Fossil Records: Show gradual changes in species over time.
- Homologous Structures: Indicate common ancestry.
- Embryological Similarities: Embryos of different species show similarities during development.
- Genetics: Demonstrates variation and inheritance at the molecular level.
- Artificial Selection: Breeding by humans mirrors natural selection.
9. Why is Lamarck’s theory considered outdated?
Answer:
Lamarck’s theory is considered outdated because:
- Modern genetics disproves the inheritance of acquired traits.
- Evolutionary changes are driven by genetic mutations and natural selection, not individual effort or use/disuse of traits.
- Experiments have failed to validate Lamarck’s principles.
10. How do Darwin and Lamarck explain the evolution of long necks in giraffes?
Answer:
- Lamarck: Suggested that giraffes stretched their necks to reach high branches, and this acquired trait was inherited.
- Darwin: Proposed that giraffes with naturally longer necks had a survival advantage, allowing them to reproduce and pass the trait on. Over generations, the population evolved longer necks.
11. What is the significance of variation in Darwin’s theory?
Answer:
Variation is essential in Darwin’s theory because it provides the raw material for natural selection. Individuals with favorable variations have a higher chance of survival and reproduction, leading to evolutionary changes in the population.
12. Discuss the concept of adaptive radiation with an example.
Answer:
Adaptive radiation occurs when a single species evolves into multiple species adapted to different environments or niches.
Example: Darwin’s finches evolved into various species with different beak shapes to exploit different food sources on the Galápagos Islands.
13. How does modern genetics support Darwin’s theory?
Answer:
Modern genetics supports Darwin’s theory by explaining the mechanisms of variation and inheritance:
- Genetic mutations introduce new traits.
- Traits are passed to offspring through DNA.
- Natural selection acts on genetic variation, favoring advantageous traits.
14. What is the significance of homologous structures in evolution?
Answer:
Homologous structures are anatomical features with similar structures but different functions, indicating common ancestry.
Example: The forelimbs of humans, whales, and bats share the same bone structure but serve different purposes, supporting Darwin’s theory of common descent.
15. Explain the importance of fossil evidence in evolutionary studies.
Answer:
Fossils provide a historical record of life on Earth. They show:
- Gradual changes in species over time.
- Transitional forms linking different groups of organisms.
- Extinct species, indicating the dynamic nature of evolution.
16. What is the concept of “inheritance of acquired traits” in Lamarckism?
Answer:
Lamarckism posits that traits acquired during an organism’s lifetime (due to use, disuse, or environmental influence) can be passed to offspring. For example, a blacksmith’s muscular arms would be inherited by his children.
17. Why did Darwin reject the idea of acquired inheritance?
Answer:
Darwin rejected acquired inheritance because it lacked empirical support. He emphasized natural selection, where inherited genetic traits, not acquired characteristics, drive evolution.
18. What are the differences between Lamarckism and Darwinism?
Answer:
| Aspect | Lamarckism | Darwinism |
|---|---|---|
| Mechanism | Use/disuse of traits | Natural selection |
| Inheritance | Acquired traits are inherited | Genetic traits are inherited |
| Randomness | Changes are purposeful | Changes occur randomly |
19. What role did Malthus’s essay play in Darwin’s theory?
Answer:
Malthus’s essay on population highlighted the struggle for resources due to overpopulation. Darwin applied this to natural selection, suggesting that only the fittest organisms survive and reproduce.
20. Describe the concept of “survival of the fittest” in Darwinism.
Answer:
“Survival of the fittest” means that individuals with traits best suited to their environment have a higher chance of survival and reproduction. Over generations, these advantageous traits become prevalent in the population.
These questions and answers provide a comprehensive understanding of the differences and implications of Lamarck’s and Darwin’s evolutionary theories.
