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🧑🏽‍🔬history of science review

Germ plasm theory

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

Germ plasm theory is the biological concept that states heredity is transmitted through germ cells, which carry genetic information separate from somatic cells. This theory emphasizes that only genetic material within the germ cells is passed on to offspring, suggesting a clear distinction between the hereditary material and the body cells of an organism. It underscores the importance of understanding heredity in relation to evolution and variation.

5 Must Know Facts For Your Next Test

  1. Germ plasm theory was first articulated by August Weismann in the late 19th century, challenging the ideas of acquired characteristics proposed by earlier evolutionary theorists.
  2. Weismann conducted experiments that demonstrated how changes in somatic cells did not affect germ cells, supporting the idea that only hereditary information in germ cells is inherited by offspring.
  3. The theory helped lay the groundwork for modern genetics by highlighting the role of chromosomes in heredity.
  4. Germ plasm theory set the stage for the understanding of genetic inheritance as a key mechanism in evolution, contrasting sharply with Lamarck's ideas about inheritance of acquired traits.
  5. This theory was influential in shaping scientific thought about evolution and genetics, reinforcing the idea that evolution occurs through changes in populations over generations rather than through individual modifications.

Review Questions

  • How does germ plasm theory contrast with Lamarck's ideas about inheritance?
    • Germ plasm theory contrasts sharply with Lamarck's ideas by asserting that heredity is solely based on genetic information contained within germ cells, while Lamarck proposed that traits acquired during an organism's life could be inherited by offspring. This means that changes made to an individual do not affect their descendants according to germ plasm theory, whereas Lamarck believed such modifications could be passed down. Therefore, germ plasm theory provided a scientific framework that refuted Lamarckian inheritance, emphasizing genetics over acquired traits.
  • In what ways did Weismann's research support germ plasm theory and challenge existing beliefs about heredity?
    • Weismann's research supported germ plasm theory by conducting experiments that demonstrated a clear separation between somatic and germ cells. He showed that changes in somatic cells do not influence germ cells, meaning characteristics acquired during an individual's life are not passed on to future generations. This challenged existing beliefs rooted in Lamarckian thought, which suggested that adaptations could be inherited. Weismann's work was pivotal in establishing genetics as a cornerstone of biological inheritance and evolution.
  • Evaluate the impact of germ plasm theory on the development of modern genetics and evolutionary biology.
    • Germ plasm theory significantly impacted modern genetics and evolutionary biology by providing a clear framework for understanding heredity based on genetic material passed through germ cells. This distinction laid the groundwork for later discoveries about DNA, chromosomes, and genetic inheritance, influencing how scientists study variation and evolution. By refuting ideas like Lamarckian inheritance, it redirected research towards population genetics and natural selection, solidifying the role of genetic mechanisms in evolutionary processes and shaping contemporary views on heredity.