The Academy's Evolution Site

The concept of biological evolution is a fundamental concept in biology. The Academies are committed to helping those interested in science understand evolution theory and how it can be applied in all areas of scientific research.

This site provides students, teachers and general readers with a range of educational resources on evolution. It contains key video clips from NOVA and WGBH's science programs on DVD.

Tree of Life

The Tree of Life, an ancient symbol, symbolizes the interconnectedness of all life. It is a symbol of love and unity across many cultures. It has many practical applications in addition to providing a framework for understanding the history of species, and how they react to changes in environmental conditions.

The earliest attempts to depict the world of biology focused on categorizing organisms into distinct categories that were identified by their physical and metabolic characteristics1. These methods rely on the sampling of different parts of organisms or short fragments of DNA, have greatly increased the diversity of a tree of Life2. However these trees are mainly composed of eukaryotes; bacterial diversity remains vastly underrepresented3,4.

By avoiding 무료 에볼루션 for direct observation and experimentation genetic techniques have allowed us to depict the Tree of Life in a more precise way. In particular, molecular methods allow us to build trees using sequenced markers, such as the small subunit ribosomal gene.

Despite the massive growth of the Tree of Life through genome sequencing, much biodiversity still awaits discovery. This is particularly true of microorganisms, which can be difficult to cultivate and are often only present in a single sample5. A recent analysis of all genomes that are known has created a rough draft of the Tree of Life, including many archaea and bacteria that have not been isolated, and their diversity is not fully understood6.

The expanded Tree of Life can be used to assess the biodiversity of a specific area and determine if certain habitats require special protection. This information can be utilized in a range of ways, from identifying the most effective medicines to combating disease to enhancing the quality of crops. The information is also valuable to conservation efforts. It helps biologists discover areas that are most likely to have species that are cryptic, which could have vital metabolic functions and are susceptible to the effects of human activity. Although funding to protect biodiversity are essential however, the most effective method to preserve the world's biodiversity is for more people in developing countries to be empowered with the knowledge to act locally in order to promote conservation from within.

Phylogeny

A phylogeny (also called an evolutionary tree) illustrates the relationship between different organisms. Scientists can construct a phylogenetic diagram that illustrates the evolution of taxonomic groups using molecular data and morphological similarities or differences. Phylogeny is essential in understanding biodiversity, evolution and genetics.

A basic phylogenetic Tree (see Figure PageIndex 10 Identifies the relationships between organisms that have similar traits and evolved from a common ancestor. These shared traits may be analogous, or homologous. Homologous traits are similar in their evolutionary path. Analogous traits could appear like they are but they don't have the same origins. Scientists combine similar traits into a grouping called a Clade. For instance, all the organisms in a clade share the characteristic of having amniotic eggs and evolved from a common ancestor which had these eggs. The clades are then connected to form a phylogenetic branch to determine which organisms have the closest relationship.

Scientists use molecular DNA or RNA data to construct a phylogenetic graph which is more precise and precise. This information is more precise than morphological information and provides evidence of the evolutionary history of an organism or group. Molecular data allows researchers to determine the number of species that share a common ancestor and to estimate their evolutionary age.

무료 에볼루션 between species are influenced by many factors, including phenotypic flexibility, a type of behavior that alters in response to unique environmental conditions. This can cause a trait to appear more similar in one species than other species, which can obscure the phylogenetic signal. However, this problem can be cured by the use of techniques such as cladistics which combine similar and homologous traits into the tree.

Additionally, phylogenetics aids determine the duration and rate at which speciation takes place. This information can assist conservation biologists in making decisions about which species to protect from extinction. It is ultimately the preservation of phylogenetic diversity which will create a complete and balanced ecosystem.

Evolutionary Theory

The fundamental concept in evolution is that organisms change over time due to their interactions with their environment. Several theories of evolutionary change have been developed by a variety of scientists, including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who believed that an organism would evolve gradually according to its requirements as well as the Swedish botanist Carolus Linnaeus (1707-1778) who designed modern hierarchical taxonomy, and Jean-Baptiste Lamarck (1744-1829) who suggested that use or disuse of traits cause changes that can be passed onto offspring.

In the 1930s and 1940s, ideas from a variety of fields -- including genetics, natural selection, and particulate inheritance - came together to form the modern evolutionary theory synthesis, which defines how evolution is triggered by the variations of genes within a population and how those variants change over time due to natural selection. This model, which incorporates genetic drift, mutations in gene flow, and sexual selection, can be mathematically described mathematically.

Recent discoveries in the field of evolutionary developmental biology have demonstrated that genetic variation can be introduced into a species by genetic drift, mutation, and reshuffling of genes in sexual reproduction, as well as through migration between populations. These processes, along with others like directional selection and genetic erosion (changes in the frequency of a genotype over time) can lead to evolution that is defined as change in the genome of the species over time, and also by changes in phenotype over time (the expression of that genotype within the individual).

Students can better understand the concept of phylogeny through incorporating evolutionary thinking into all aspects of biology. In a recent study by Grunspan and colleagues. It was found that teaching students about the evidence for evolution increased their acceptance of evolution during an undergraduate biology course. For more details on how to teach about evolution look up The Evolutionary Power of Biology in all Areas of Biology or Thinking Evolutionarily as a Framework for Infusing Evolution into Life Sciences Education.

Evolution in Action

Scientists have studied evolution by looking in the past--analyzing fossils and comparing species. They also observe living organisms. Evolution is not a past event; it is a process that continues today. Bacteria transform and resist antibiotics, viruses re-invent themselves and elude new medications and animals change their behavior in response to the changing climate. The results are often visible.


It wasn't until late 1980s that biologists began to realize that natural selection was in action. The key is that various traits confer different rates of survival and reproduction (differential fitness) and are transferred from one generation to the next.

In the past, if an allele - the genetic sequence that determines colour appeared in a population of organisms that interbred, it could become more prevalent than any other allele. Over time, this would mean that the number of moths that have black pigmentation in a group could increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.

It is easier to observe evolution when a species, such as bacteria, has a rapid generation turnover. Since 1988 biologist Richard Lenski has been tracking twelve populations of E. Coli that descended from a single strain. samples of each population are taken on a regular basis and over fifty thousand generations have passed.

Lenski's research has shown that mutations can drastically alter the speed at the rate at which a population reproduces, and consequently, the rate at which it evolves. It also shows evolution takes time, something that is hard for some to accept.

Another example of microevolution is that mosquito genes that are resistant to pesticides are more prevalent in populations in which insecticides are utilized. This is because pesticides cause a selective pressure which favors those who have resistant genotypes.

The speed of evolution taking place has led to a growing appreciation of its importance in a world that is shaped by human activity, including climate changes, pollution and the loss of habitats which prevent many species from adapting. Understanding evolution will aid you in making better decisions about the future of the planet and its inhabitants.