![]() ![]() The sequence of bases along a particular DNA molecule specifies the genetic information, in a manner similar to a sequence of letters spelling out a sentence. DNA is a long biopolymer composed of four types of bases. Heritable traits are passed from one generation to the next via DNA, a molecule that encodes genetic information. However, some people tan more easily than others, due to differences in genotypic variation a striking example are people with the inherited trait of albinism, who do not tan at all and are very sensitive to sunburn. For example, suntanned skin comes from the interaction between a person's genotype and sunlight thus, suntans are not passed on to people's children. As a result, many aspects of an organism's phenotype are not inherited. These traits come from the interaction of its genotype with the environment. The complete set of observable traits that make up the structure and behaviour of an organism is called its phenotype. Inherited traits are controlled by genes and the complete set of genes within an organism's genome (genetic material) is called its genotype. ![]() In humans, for example, eye colour is an inherited characteristic and an individual might inherit the "brown-eye trait" from one of their parents. Bases are in the centre, surrounded by phosphate–sugar chains in a double helix.Įvolution in organisms occurs through changes in heritable traits-the inherited characteristics of an organism. įurther information: Introduction to genetics, Genetics, and Heredity DNA structure. Their discoveries have influenced not just the development of biology but numerous other scientific and industrial fields, including agriculture, medicine, and computer science. Įvolutionary biologists have continued to study various aspects of evolution by forming and testing hypotheses as well as constructing theories based on evidence from the field or laboratory and on data generated by the methods of mathematical and theoretical biology. ![]() Morphological and biochemical traits tend to be more similar among species that share a more recent common ancestor, which historically was used to reconstruct phylogenetic trees, although direct comparison of genetic sequences is a more common method today. Existing patterns of biodiversity have been shaped by repeated formations of new species ( speciation), changes within species ( anagenesis), and loss of species ( extinction) throughout the evolutionary history of life on Earth. The fossil record includes a progression from early biogenic graphite to microbial mat fossils to fossilised multicellular organisms. Īll life on Earth-including humanity-shares a last universal common ancestor (LUCA), which lived approximately 3.5–3.8 billion years ago. In the early 20th century, other competing ideas of evolution were refuted as the modern synthesis concluded Darwinian evolution acts on Mendelian genetic variation. In successive generations, members of a population are therefore more likely to be replaced by the offspring of parents with favourable characteristics for that environment. Evolution by natural selection is established by observable facts about living organisms: (1) more offspring are often produced than can possibly survive (2) traits vary among individuals with respect to their morphology, physiology, and behaviour (3) different traits confer different rates of survival and reproduction (differential fitness) and (4) traits can be passed from generation to generation ( heritability of fitness). The theory of evolution by natural selection was conceived independently by Charles Darwin and Alfred Russel Wallace in the mid-19th century and was set out in detail in Darwin's book On the Origin of Species. It is this process of evolution that has given rise to biodiversity at every level of biological organisation. Evolution occurs when evolutionary processes such as natural selection (including sexual selection) and genetic drift act on this variation, resulting in certain characteristics becoming more or less common within a population over successive generations. Genetic variation tends to exist within any given population as a result of genetic mutation and recombination. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. In biology, evolution is the change in heritable characteristics of biological populations over successive generations. ![]()
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