On page 160, Dr. Moalem discusses the effect of choline in pregnant mice's diets. This study found that the added choline caused the production of cell division in the brain's memory center to continue, resulting in greater memory powers for the newborn mice. He goes on to describe how different environmental influences during pregnancy can also affect the phenotypes of other newborn organisms. He mentions voles, Daphnias, locusts, and lizards.
This idea of the environment affecting the the characteristics of specific organisms in a short time span seems to contradict a lot of what we've learned about Darwinian evolution. Instead, it seems to lend more evidence to the Lamarckian theory of evolution.
What are Darwin's and Lamarck's theories of evolution, and why they are different? Explain why these findings described on pages 160-161 do not go against Darwin's theory of evolution. Be sure to include the idea of the regulation of gene expression.
Additionally, relate this entire concept to Big Idea #1 (The process of evolution drives the diversity and unity of life). How does gene expression as seen in these listed examples show both diversity and unity as a result of evolution?
Carolyn Fan (cfan3@students.d125.org)
Jean-Baptiste Lamarck proposed that organisms could pass on to their offspring the traits that were acquired during their lifetime. This has come to be known as “Inheritance of Acquired Characteristics”. On the other hand, Charles Darwin recognized the main mechanism for evolution as natural selection: the process by which favorable heritable traits become more common in successive generations of a population and unfavorable heritable traits become less common. That means those who are more fit to the selective pressure will reproduce more descendants than those who are less fit. Lamarck thought that changes were acquired during the life of a parent organism and then transmitted to their offspring, while Darwin analyzed that changes were already present in the parent organisms and that the best adapted to the environment to survive and to reproduce those who inherited the favorable traits.
ReplyDeleteSome of the findings by researchers who study all kinds of animals have noted the ability of some organisms to survive and to reproduce the offsprings that was fit-- the Darwin’s theory of evolution). For example, one species of lizard is born with a long tail and big body to make themselves less likely to be snake food in a snake-filled world (161). This adaption expresses that the characteristics of offspring are controlled by epigenetic effects that occur during fetal development. The way gene expression expressed does get changed while the DNA doesn’t. However, the phenomenon the mother's experiences influencing gene expression in her offspring is called a maternal effect (162). The ability of mother to influence gene expression in her offspring was the trait Charles Darwin’s theory talked about. The success of Charles Darwin’s theory was facilitated by a theory of inheritance, which made the link between natural selection and evolutionary change particularly direct, which also applies to the development of a maternal effect.
It has been proposed that maternal effects are important for the evolution of adaptive responses to environmental heterogeneity. In the field of genetics, maternal effects occur when an organism shows the phenotype expected from the genotype of the mother, often due to the mother supplying mRNA or proteins to the egg. Maternal effects can also be caused by the maternal environment independent of genotype, sometimes controlling the size, sex, or behavior of the offspring.
Then I can relate this concept of maternal effect to big idea #1 (The process of evolution drives the diversity and unity of life) because populations of organisms continue to evolve due to maternal effect. This evidence supports the idea that evolution has occurred in all species. Scientific evidence supports the idea that evolution continues to occur by observation of directional phenotypic change in a population.
(Hyung Eun Lee, helee4@students.d125.org)
Outside Source 1: http://nursingplanet.com/theory/Evolution_theory.html
Outside Source 2: http://www.ndsu.edu/pubweb/~mcclean/plsc431/maternal/maternal1.htm