COMPARING LAMARCK & DARWIN Both scientists agreed that organisms have changed over time. What they disagreed about was WHEN organisms changed.

LAMARCK Lamarck argued that organisms constantly “improve” themselves in order to better “fit” into their environment. EX: Giraffes stretched their necks in order to reach food in the trees after the grasses became depleted. Their necks grew longer during their lifetime, and they passed their longer necks on to their offspring.

DARWIN Darwin argued that variations (differences in traits) always exist. Once an environment changes, only those organisms with “favorable traits” would be able to survive in the new environment. EX: When grass was depleted, only the giraffes that had longer necks could reach food higher in the trees. They lived longer, made more offspring, and their offspring also had those longer necks.

DNA’s ROLE IN THIS Lamarck did not know about DNA. We are born with our DNA intact, and we can not change our DNA during our lifetime. Since we can’t change our DNA, we cannot possibly acquire new traits and pass them on to offspring.

VESTIGIAL ORGANS Vestigial organs are organs that once were necessary for survival, but due to changes in the environment, they are no longer needed for survival. They are beginning to disappear from the gene pool. EX: in humans - the appendix, wisdom teeth, the ability to see colors, hair, etc.

LAMARCK and VESTIGIAL ORGANS Lamarck would argue that we changed during our lifetime (to better fit in our environment) and we grew more hair, wisdom teeth, and an appendix. Once the environment changed, and we no longer needed those organs, we stopped using them. Since we stopped using them, they are beginning to become smaller/weaker, and are disappearing from our gene pool.

DARWIN and VESTIGIAL ORGANS Darwin would argue that at some point, it was important to have wisdom teeth/appendix/hair. Those organisms with those traits lived longer, had more offspring with those traits. Once the environment changed and we no longer need those traits, “nature” is not selecting us to survive based on those traits. Organisms both with and without them are breeding, creating offspring with reduced versions.