Origin And Evolution Of Life Pdf

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The Origin and Early Evolution of Life: Where, When and How?

Evolution , theory in biology postulating that the various types of plants, animals, and other living things on Earth have their origin in other preexisting types and that the distinguishable differences are due to modifications in successive generations. The theory of evolution is one of the fundamental keystones of modern biological theory. The diversity of the living world is staggering.

More than 2 million existing species of organisms have been named and described; many more remain to be discovered—from 10 million to 30 million, according to some estimates. The virtually infinite variations on life are the fruit of the evolutionary process. All living creatures are related by descent from common ancestors.

Humans and other mammals descend from shrewlike creatures that lived more than million years ago; mammals, birds, reptiles, amphibians, and fishes share as ancestors aquatic worms that lived million years ago; and all plants and animals derive from bacteria-like microorganisms that originated more than 3 billion years ago. Biological evolution is a process of descent with modification. Lineages of organisms change through generations; diversity arises because the lineages that descend from common ancestors diverge through time.

The 19th-century English naturalist Charles Darwin argued that organisms come about by evolution, and he provided a scientific explanation , essentially correct but incomplete, of how evolution occurs and why it is that organisms have features—such as wings, eyes, and kidneys—clearly structured to serve specific functions.

Natural selection was the fundamental concept in his explanation. Natural selection occurs because individuals having more-useful traits, such as more-acute vision or swifter legs, survive better and produce more progeny than individuals with less-favourable traits.

Genetics , a science born in the 20th century, reveals in detail how natural selection works and led to the development of the modern theory of evolution. Beginning in the s, a related scientific discipline , molecular biology , enormously advanced knowledge of biological evolution and made it possible to investigate detailed problems that had seemed completely out of reach only a short time previously—for example, how similar the gene s of humans and chimpanzees might be they differ in about 1—2 percent of the units that make up the genes.

This article discusses evolution as it applies generally to living things. For a discussion of human evolution, see the article human evolution. For a more complete treatment of a discipline that has proved essential to the study of evolution, see the articles genetics, human and heredity. Specific aspects of evolution are discussed in the articles coloration and mimicry.

Applications of evolutionary theory to plant and animal breeding are discussed in the articles plant breeding and animal breeding. A detailed discussion of the life and thought of Charles Darwin is found in the article Darwin, Charles.

Darwin and other 19th-century biologists found compelling evidence for biological evolution in the comparative study of living organisms, in their geographic distribution, and in the fossil remains of extinct organisms. The amount of information about evolutionary history stored in the DNA and proteins of living things is virtually unlimited; scientists can reconstruct any detail of the evolutionary history of life by investing sufficient time and laboratory resources.

Evolutionists no longer are concerned with obtaining evidence to support the fact of evolution but rather are concerned with what sorts of knowledge can be obtained from different sources of evidence. The following sections identify the most productive of these sources and illustrate the types of information they have provided.

Evolution Article Media Additional Info. Article Contents. Print print Print. Table Of Contents. While every effort has been made to follow citation style rules, there may be some discrepancies.

Please refer to the appropriate style manual or other sources if you have any questions. Facebook Twitter. Give Feedback External Websites. Let us know if you have suggestions to improve this article requires login. External Websites. Your Genome - What is evolution?

Articles from Britannica Encyclopedias for elementary and high school students. Francisco Jose Ayala Francisco J. See Article History. The geologic time scale from million years ago to the present, showing major evolutionary events.

Get a Britannica Premium subscription and gain access to exclusive content. Subscribe Now. Overview of Charles Darwin's life, with a focus on his work involving evolution. Load Next Page.

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Evolution , theory in biology postulating that the various types of plants, animals, and other living things on Earth have their origin in other preexisting types and that the distinguishable differences are due to modifications in successive generations. The theory of evolution is one of the fundamental keystones of modern biological theory. The diversity of the living world is staggering. More than 2 million existing species of organisms have been named and described; many more remain to be discovered—from 10 million to 30 million, according to some estimates. The virtually infinite variations on life are the fruit of the evolutionary process. All living creatures are related by descent from common ancestors. Humans and other mammals descend from shrewlike creatures that lived more than million years ago; mammals, birds, reptiles, amphibians, and fishes share as ancestors aquatic worms that lived million years ago; and all plants and animals derive from bacteria-like microorganisms that originated more than 3 billion years ago.

Thank you for visiting nature. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. The evolution of RNA is likely to have played an important role in the very early history of life on Earth but it is doubtful that life began with RNA.


PDF | Life is an inordinately complex unsolved puzzle. Despite significant theoretical progress, experimental anomalies, paradoxes, and.


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Gordon C. Mills, Malcolm Lancaster, Walter L. The American Biology Teacher 1 February ; 55 2 : 78—

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4 Response
  1. Christin D.

    Human evolution is the lengthy process of change by which people originated from apelike ancestors.

  2. Bedsporniscmi

    Building web services with java making sense of xml pdf the yusa guide to balance mind body spirit pdf

  3. Miranda N.

    compounds, until they originated living organisms. However, the extension of the evolution to the molecular world as the first chapter of the evolution of life only.

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