Charles Darwin The Origin of Species Lecture

The Origin species was published in year 1859 by Charles Darwin ,It introduced the theory that populations evolve over the course of generations through a process of natural selection,Darwin's book was the culmination of evidence he had accumulated on the voyage of the Beagle in the 1830s and expanded through continuing investigations and experiments after his return.

Darwin's theory is based on key observations and inferences drawn from them:

* Species have great fertility. They have more offspring than can grow to adulthood.
* Populations remain roughly the same size, with small changes.
* Food resources are limited, but are relatively stable over time.
* An implicit struggle for survival ensues.
* In sexually reproducing species, generally no two individuals are identical.
* Some of these variations directly impact the ability of an individual to survive in a given environment.
* Much of this variation is inheritable.
* Individuals less suited to the environment are less likely to survive and less likely to reproduce, while individuals more suited to the environment are more likely to survive and more likely to reproduce.
* The individuals that survive are most likely to leave their inheritable traits to future generations.
* This slowly effected process results in populations that adapt to the environment over time, and ultimately, after interminable generations, these variations accumulate to form new varieties, and ultimately, new species.





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Natural Selection Leture

Natural selection is the process by which favorable heritable traits become more common in sucessiove genrations of a population of reproducing organisms,and unfavorable heritable traits become less common, due to differntial reproduction of genotypes,Natural selection acts on the phenotype, or the observable characteristics of an organism, such that individuals with favorable phenotypes are more likely to survive and reproduce than those with less favorable phenotypes. The phenotype's genetic basis, genotype associated with the favorable phenotype, will increase in frequency over the following generations. Over time, this process may result in adaptations that specialize organisms for particular ecological niches and may eventually result in the emergence of new species. In other words, natural selection is the mechanism by which evolution may take place in a population of a specific organism.The term was introduced by Charles Darwin in his groundbreaking 1859 book The Origin of Species in which natural selection was described by analogy to artificial selection, a process by which animals with traits considered desirable by human breeders are systematically favored for reproduction. The concept of natural selection was originally developed in the absence of a valid theory of inheritance; at the time of Darwin's writing, nothing was known of modern genetics. Although Gregor Mendel, the father of modern genetics, was a contemporary of Darwin's, his work would lie in obscurity until the early 20th century. The union of traditional Darwinian evolution with subsequent discoveries in classical and molecular genetics is termed the modern evolutionary synthesis. Although other mechanisms of molecular evolution, such as the neutral theory advanced by Motoo Kimura, have been identified as important causes of genetic diversity, natural selection remains the single primary explanation for adaptive evolution.


Natural selection part 1





Natural selection part 2







Natural selection part 3