**Historical Development of Natural Selection:**
– Aristotle, Empedocles, and Lucretius proposed early ideas on natural selection.
– Lamarck introduced the concept of inheritance of acquired characteristics.
– Pre-Darwinian theories by various scholars questioned survival of the fittest.
**Concepts and Mechanisms of Natural Selection:**
– Definition and key mechanisms of natural selection.
– Microevolution and macroevolution explained through natural selection.
– Mechanism of differential survival and reproduction based on phenotype differences.
**Impact of Environment on Natural Selection:**
– Traits selected based on adaptation to environments.
– Sexual selection and fecundity selection in natural selection.
– Changes in the environment leading to the rise of new species.
**Contributions to Modern Biology and Evolutionary Synthesis:**
– Darwin’s theory of natural selection and its impact on modern biology.
– The modern synthesis integrating Darwinian evolution with genetics.
– Evolutionary developmental biology and key contributors to the field.
**Varieties and Effects of Natural Selection:**
– Different types of natural selection like stabilizing, directional, and disruptive.
– Mechanisms affecting genetic diversity such as purifying and balancing selection.
– Selection based on life cycle stage, unit of selection, and resources being competed for.
Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations. Charles Darwin popularised the term "natural selection", contrasting it with artificial selection, which is intentional, whereas natural selection is not.
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Variation of traits, both genotypic and phenotypic, exists within all populations of organisms. However, some traits are more likely to facilitate survival and reproductive success. Thus, these traits are passed onto the next generation. These traits can also become more common within a population if the environment that favours these traits remain fixed. If new traits become more favored due to changes in a specific niche, microevolution occurs. If new traits become more favored due to changes in the broader environment, macroevolution occurs. Sometimes, new species can arise especially if these new traits are radically different from the traits possessed by their predecessors.
The likelihood of these traits being 'selected' and passed down are determined by many factors. Some are likely to be passed down because they adapt well to their environments. Others are passed down because these traits are actively preferred by mating partners, which is known as sexual selection. Female bodies also prefer traits that confer the lowest cost to their reproductive health, which is known as fecundity selection.
Natural selection is a cornerstone of modern biology. The concept, published by Darwin and Alfred Russel Wallace in a joint presentation of papers in 1858, was elaborated in Darwin's influential 1859 book On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. He described natural selection as analogous to artificial selection, a process by which animals and plants with traits considered desirable by human breeders are systematically favoured for reproduction. The concept of natural selection originally developed in the absence of a valid theory of heredity; at the time of Darwin's writing, science had yet to develop modern theories of genetics. The union of traditional Darwinian evolution with subsequent discoveries in classical genetics formed the modern synthesis of the mid-20th century. The addition of molecular genetics has led to evolutionary developmental biology, which explains evolution at the molecular level. While genotypes can slowly change by random genetic drift, natural selection remains the primary explanation for adaptive evolution.