Introduction to evolution

In <a href="/facts/Biology/1M1ee3pB">biology</a>, evolution is the process of change in all forms of <a href="/facts/Life/DNw7NUId">life</a> over generations, and <a href="/facts/Evolutionary_biology/8tBoG55U">evolutionary biology</a> is the study of how <a href="/facts/Evolution/qE5amP6a">evolution</a> occurs. Biological <a href="/facts/Population/ArxshNuB">populations</a> evolve through <a href="/facts/Genetics/bu8wne0A">genetic</a> changes that correspond to changes in the <a href="/facts/Organism/j8JkL09u">organisms</a>' <a href="/facts/Phenotypic_trait/seYSUTul">observable traits</a>. Genetic changes include <a href="/facts/Mutations/Ee4NnWbY">mutations</a>, which are caused by damage or replication errors in organisms' <a href="/facts/DNA/nB89Iauz">DNA</a>. As the <a href="/facts/Genetic_variation/f2wzYLbI">genetic variation</a> of a population <a href="/facts/Genetic_drift/lvoEEctX">drifts</a> randomly over generations, <a href="/facts/Natural_selection/JXTte6en">natural selection</a> gradually leads traits to become more or less common based on the relative <a href="/facts/Reproductive_success/BjHIUg2l">reproductive success</a> of organisms with those traits.
The <a href="/facts/Age_of_the_Earth/MxNh2Q11">age of the Earth</a> is about 4.5 billion years. The earliest undisputed evidence of life on Earth dates from at least 3.5 billion years ago. Evolution does not attempt to explain the origin of life (covered instead by <a href="/facts/Abiogenesis/BvAmLPQP">abiogenesis</a>), but it does explain how early lifeforms evolved into the complex ecosystem that we see today. Based on the similarities between all present-day organisms, all life on <a href="/facts/Earth/HLLmDfj0">Earth</a> is assumed to have originated through <a href="/facts/Common_descent/bwEgMu7F">common descent</a> from a <a href="/facts/Last_universal_ancestor/pnpExNAU">last universal ancestor</a> from which all known <a href="/facts/Species/oDg6b96r">species</a> have diverged through the process of evolution.
All individuals have hereditary material in the form of <a href="/facts/Gene/e1swwPY6">genes</a> received from their parents, which they pass on to any offspring. Among offspring there are variations of genes due to the introduction of new genes via random changes called mutations or via reshuffling of existing genes during <a href="/facts/Sexual_reproduction/hmsXy53s">sexual reproduction</a>. The offspring differs from the parent in minor random ways. If those differences are helpful, the offspring is more likely to survive and reproduce. This means that more offspring in the next generation will have that helpful difference and individuals will not have equal chances of <a href="/facts/Reproduction/nNu0F5Dy">reproductive</a> success. In this way, traits that result in organisms being better <a href="/facts/Adaptation/5K2gNpDB">adapted</a> to their living conditions become more common in descendant populations. These differences accumulate resulting in changes within the population. This process is responsible for the many diverse life forms in the world.
The modern understanding of evolution began with the 1859 publication of <a href="/facts/Charles_Darwin/uwDLGItY">Charles Darwin</a>'s <a href="/facts/On_the_Origin_of_Species/zTMxkKVY">On the Origin of Species</a>. In addition, <a href="/facts/Gregor_Mendel/4UpILWAz">Gregor Mendel</a>'s work with plants, between 1856 and 1863, helped to explain the hereditary patterns of <a href="/facts/Genetics/bu8wne0A">genetics</a>. Fossil discoveries in <a href="/facts/Palaeontology/60n5yldd">palaeontology</a>, advances in <a href="/facts/Population_genetics/v55qAnKu">population genetics</a> and a global network of scientific research have provided further details into the mechanisms of evolution. Scientists now have a good understanding of the origin of new species (<a href="/facts/Speciation/pmRTQbTK">speciation</a>) and have observed the speciation process in the laboratory and in the wild. Evolution is the principal <a href="/facts/Scientific_theory/moMsLrUn">scientific theory</a> that <a href="/facts/Biologist/yJJGXyKR">biologists</a> use to understand life and is used in many disciplines, including <a href="/facts/Medicine/2fnp90Je">medicine</a>, <a href="/facts/Psychology/duoqW7Sz">psychology</a>, <a href="/facts/Conservation_biology/S2693mIF">conservation biology</a>, <a href="/facts/Anthropology/W6WK1C3a">anthropology</a>, <a href="/facts/Forensic_science/4upVa2vB">forensics</a>, <a href="/facts/Agriculture/TGztqzJs">agriculture</a> and other <a href="/facts/Sociocultural_evolution/7KgkjD6H">social-cultural</a> applications.

Introduction to evolution open-in-new

Introduction to evolution