In the early 1800s, French naturalist Jean Baptiste Lamarck suggested that the best explanation for the relationship of fossils to current organisms is that life evolves. He proposed that by using or not using its body parts, an individual may change its traits and then pass those changes on to its offspring. He suggested, for instance, that the ancestors of the giraffe had lengthened their necks by stretching higher and higher into the trees to reach leaves. Evaluate Lamarck's hypotheses from the perspective of present-day scientific knowledge.

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Hi everyone welcome back, Here's our next question. It says jean Baptiste. Lamark proposed that certain organs were specially developed to address some environmental needs. That developed traits are hereditary and can be passed on to the next offspring. This proposition was called so often. When you learn about Lamarque we recall we think of the example of the giraffe. And he thought that as giraffe stretched to reach leaves and tall trees there next became longer during the lifetime of the organism. And he thought that they could pass that longer neck onto their offspring. So he had the idea that acquired traits were heritable. And he thought that these traits developed because organisms structures that were used more often would develop more whereas the ones that were used less would you know sort of drop away become less. And so his theory is called the theory of use and disuse. Which is here is choice A. Because it has to do with body parts structures being used or disused and that affecting their development. But let's just walk through other answer choices to understand why they're not correct. Choice B. Says natural selection. Ah Well, natural selection became famous from Darwin's work as he incorporated that into his understanding of evolution. Natural selection says that differential survival and reproduction of individuals is due to differences in phenotype. So natural selection also, you could say that the giraffe's long neck is an example of natural selection. But whereas Lamarque saw it as the draft during its lifetime. Its neck became longer and pass that on natural selection would say giraffes born with the phenotype of a longer neck have an advantage They get more food. They're more likely to survive to reproduce and pass the genes for that phenotype onto their offspring. So observing a similar phenomenon but slightly different explanation of what causes it. That's why natural selection doesn't describe remarks ideas. Then we move on to toy C. And Joy C. Says descent with modification. When we think about that we recall the descent with modification first the idea that species change over time. This gives rise to new species that share a common ancestor and it's similar to the idea of use and disuse. And you see species changing over time. Both involved the idea of the giraffe's neck getting longer over time. But descent with modification involves this change over lots of time over the time of the species. Whereas Lamar kind of looked at changes occurring in the actual lifetime of an individual influenced by the lifestyle, the actions of that individual. So less of a long period of time than idea of descent with modification. So descent with modification is not a description of remarks idea and finally, we have choice d the origin of species. This is the title of Darwin's book where he proposed his explanation of evolution. So not part of the Marx ideas and not our answer. So again. Uh Lamark proposed that certain organs were specially developed to address some environmental needs to develop traits of hereditary and can be passed on to the next offspring. This proposition was called choice, a theory of use and disuse. See you in the next video.

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Key Concepts

Lamarckism

Natural Selection

Modern Genetics