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Lamarckism

genetic evolution individuals fixed

Chevalier de Lamarck was a French naturalist and invertebrate zoologist who lived from 1844-1829. He is best known for a theory of evolution developed in his book, Philosophie zoologique, published in 1809. This theory, known today as Lamarckism, is based on the socalled "inheritance of acquired traits," meaning that characteristics that an organism may develop during its lifetime are heritable, and can be passed on to its progeny.

The anatomical, biochemical, and behavioral characteristics that an individual organism displays as its develops through life is known as its phenotype. However, the phenotype that an individual actually develops is somewhat conditional, and is based on two key factors: (1) the fixed genetic potential of the org anism (or its genotype; this refers to the specific qualities of its genetic material, or DNA [deoxyribonucleic acid]); and (2) the environmental conditions which an organism experiences as it grows. For example, an individual plant (with a particular, fixed genotype) that is well supplied with nutrients, moisture, and light throughout its life will grow larger and will produce more seeds than if that same plant did not experience such beneficial conditions. Conditional developmental possibilities as these are now known to be due to differing expressions of the genetic potenti al of the individual (biologists refer to the variable expression of the genome of an organism, as influenced by environmental conditions encountered during its development, as "phenotypic plasticity."

However, at the time of Lamarck and other biologists of the late eighteenth and nineteenth centuries the mechanisms of inheritance were not known (this includes Charles Darwin and Alfred Russel Wallace, the co-discoverers of the theory of evolution by natural selection, first published in 1859). These scientists thought that the developmental contingencies of individual organisms (which they called "acquired traits") were not initially fixed genetically, but that they could somehow become incorporated into the genetic make-up of individuals, and thereby be passed along to their offspring, so that evolution could occur. For example, if the ancestors of giraffes has to stretch vigorously to reach their food of tree foliage high in the canopy, this physical act might somehow have caused the individual animals to develop somewhat longer necks. This "acquired" trait somehow became fixed in the genetic complement of those individuals, to be passed on to their offspring, who then also had longer necks. Eventually, this presumed mechanism of evolution could have resulted in the appearance of the modern, extremely long-necked giraffe.

Modern biologists, however, have a good understanding of the biochemical nature of inheritance. They know that phenotypic plasticity is only a reflection of the variable, but strongly fixed genetic potential that exists in all individuals. Therefore, the idea of the inheritance of acquired traits is no longer influential in evolutionary s cience. Instead, biologists believe that evolution largely proceeds through the differential survival and reproduction of individuals whose genetic complement favors these characters in particular environments, compared with other, "less-fit" individuals of their population. If the phenotypic advantages of the "more-fit" individuals are due to genetically fixed traits, they will be passed on to their offspring. This results in genetic change at the population level, which is the definition of evolution. This is, essentially, the theory of evolution by natural selection, first proposed by Darwin and Wallace in 1859.

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over 7 years ago

"lived from 1844-1829" should be "lived from 1744-1829"

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about 6 years ago

Isn't his name Jean-Baptiste?

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over 6 years ago

why lamarcks theory became fail?

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over 6 years ago

why lamarcks theory became fail?

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about 2 years ago

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over 4 years ago

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about 5 years ago

A word 'forgotten' in cancer research is cell dedifferentiation, going backward as they become more malignant, using less and less oxygen (Warberg effect), expressing growth receptors of an earlier time in embryogenesis going forward. They go from endocrine stimulated to juxtacrine to paracrine to autocrine i.e. become more autonomous before metastasising. If a blastula used oxygen and one of it's totipotent cells incurred ROS damage to DNA, the mutations could spread right through the three germ lines and into many different cell types. Would a hypothetical 'wild type' cancer go back, though a series of metastasis, to a blastula like 'organism'. Blastulas contain within their blastacoel primordial germ cells, one example of dedifferentiation.
Blastula cells inserted into just about any part of a mouse's body become tumours. During male bird and lizard embryogenesis the primordial germ cells grow distal to the seminiferous tubules then migrate to the tubules and enter therein by a process so similar
to metastasis that it IS metastasis. Fill in the gaps in between and no Weissman barrier.
Everybody is looking under the wrong rock. The answers, in mammals at least, are in CANCER
which is a gross stuff up of all of the mechanisms of evolution and VERY complex unlike the puerile, simplistic accidental mutation in the 'germ plasma' which might just happen to be selected for if DAWKINS is right.

Lots of my stuff on eHealth.forum Breast Cancer Nodules. Starting 4th April after my lock out for blasphemy expires breastcancer.org Alternative Therapy 'Why Research CANNOT Find Cure' Nodules. Already a good line up of support and ridicule posts wondering where I am. Hoping big Pharma and researchers get sucked in to get rid of this evil pest once and for all before he has an adverse effect on bottom line. Should be good for a giggle. Might have to stick my head in gas oven if I've got this all ballsed up.

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over 5 years ago

Lamarck believed that we ordain or gain evolution through nature which pressure's us to evolve and is eventually passed down the generation.

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about 8 years ago

explain how acquired characters can be transfer from parent to offspring.