Reference
- EvolutionIn biology, theory that a species undergoes gradual changes to survive and reproduce in a competitive, and often changing, environment, and that a new species is the result of change from the ancestral forms. In the early 1800s French biologist Jean Lamarck began to develop evolutionary theory. In the mid-1800s English naturalists Charles Darwin and A.R. Wallace developed the same theory on evolution and in 1859 Darwin published the ground-breaking On the Origin of Species. Darwin observed that organisms produce far more offspring than they need to maintain the population. Yet most populations remain relatively constant in numbers because of predation, disease and starvation. Consequently, individuals compete for survival. Darwin argued that each organism was a unique combination of genetic variations. Each individual has different genes and is distinct from the others. Some individuals will be better suited to survive in the existing conditions: these 'fitter' individuals are more likely to breed and pass their advantageous genes on to their offspring through the process of heredity. Over many generations, individuals with favourable characteristics will build up at the expense of those lacking them. This process is called natural selection. In time, more variations will lead to the evolution of a new species. Evidence for the theory of natural selection is that dated fossil remains show that life did not arise at once, but as a gradual change from one type of organism into another. Other evidence for evolution involves the structures of different animals or plants that show such similarity it is highly probable they evolved from a common ancestor. The bones in the wing of a bird, the arm of a primate and the paddle of a whale, for example, show remarkable similarity. Equally, many proteins in organisms are fundamentally the same and we share common genes. Present-day evolutionary theory is largely derived from the work of Darwin and Austrian naturalist Gregor Mendel and maintains that in any population or gene pool, there is variation, including random mutation, in genetic forms and characteristics.
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Perspectives
Evolution
The most trusted nonfiction series on the market, Eyewitness Books provide an in-depth, comprehensive look at their subjects with a unique integration of words and pictures. Eyewitness Evolution is DK's classic look at Charles Darwin and the theory of natural selection, now reissued with a CD and wall chart.
Evolution
Evolution is the process that created the terrible teeth of Tyrannosaurus rex and the complex human brain, clever enough to understand the workings of nature. Young readers will learn how a British naturalist named Charles Darwin studied nature and developed his now-famous concepts of natural selection and survival of the fittest. And how modern-day science has added to our understanding of the theory of evolution. Can something as complex and wondrous as the natural world be explained by a simple theory? The answer is yes, and now Evolution explains how in a way that makes it easy to understand.
Evolution vs. Creationism
More than eighty years after the Scopes trial, the debate over teaching evolution continues in spite of the emptiness of the creationist positions. This accessible resource, now completely revised and updated, provides an essential introduction to the ongoing dispute's many facets--the scientific evidence for evolution, the legal and educational basis for its teaching, and the various religious points of view--as well as a concise history of the evolution-creationism controversy. This second edition also contains a discussion of the legal history, updated to include the seminal case of Kitzmiller v. Dover as well as a new chapter on public opinion and media coverage.
The Evolution of Extreme Life
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Life is even more adaptable than Darwin could have known. In this episode, investigate extremophiles - organisms that flourish in extreme conditions. These have made biologists rethink the limitations of life on Earth. From bacteria existing miles underground that divide once every 10,000 years to creatures thriving next to superheated undersea volcanoes, life is programmed to adapt and survive.
Gene Editing and Directed Evolution
- Kanopy This link opens in a new windowDarwin contrasted natural selection with artificial selection - the time-tested techniques for selective breeding that promote desired traits in plants and animals. See how far we've come with 21st-century tools such as CRISPR, which allows precise edits to the DNA sequence of any species. Evaluate the promise and perils of this technology, which lets us take evolution into our own hands.
Human Evolution in All Directions
- Kanopy This link opens in a new windowZoom in on the branch of the Tree of Life that gave rise to our species. Fossil discoveries and insights from DNA have led researchers to abandon the iconic image of a linear progression from hunched apes to upright humans. In its place is a much more intertwined tree for humans and their closest living and extinct relatives, including Neanderthals and the recently discovered Denisovans.
Online Resources
- Synthetic evolutionThe combination of modern biotechnologies such as DNA synthesis, λ red recombineering, CRISPR-based editing and next-generation high-throughput sequencing increasingly enables precise manipulation of genes and genomes. Beyond rational design, these technologies also enable the targeted, and potentially continuous, introduction of multiple mutations. While this might seem to be merely a return to natural selection, the ability to target evolution greatly reduces fitness burdens and focuses mutation and selection on those genes and traits that best contribute to a desired phenotype, ultimately throwing evolution into fast forward.
- What drives parallel evolution?: How population size and mutational variation contribute to repeated evolutionParallel evolution is the repeated evolution of the same phenotype or genotype in evolutionarily independent populations. Here, we use evolve-and-resequence experiments with bacteria and yeast to dissect the drivers of parallel evolution at the gene level. A meta-analysis shows that parallel evolution is often rare, but there is a positive relationship between population size and the probability of parallelism. We present a modeling approach to estimate the contributions of mutational and selective heterogeneity across a genome to parallel evolution. We show that, for two experiments, mutation contributes between ∼10 and 45%, respectively, of the variation associated with selection. Parallel evolution cannot, therefore, be interpreted as a phenomenon driven by selection alone; it must also incorporate information on heterogeneity in mutation rates along the genome. More broadly, the work discussed here helps lay the groundwork for a more sophisticated, empirically grounded theory of parallel evolution.
Genome Mutations: Evolution’s Raw Material
- Kanopy This link opens in a new windowThe arrival of genetics in the early 20th century addressed what Darwin did not know about inheritance, but there was more to uncover: How do genes function, and where do variations come from? Trace the discovery of DNA as the carrier of genetic information and the realization that mutations and other structural changes in DNA are a source of the modifications that underlie natural selection.