The Academy's Evolution Site

The concept of biological evolution is a fundamental concept in biology. The Academies have been active for a long time in helping people who are interested in science understand the theory of evolution and how it influences all areas of scientific exploration.

This site provides teachers, students and general readers with a wide range of educational resources on evolution. It contains the most important 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 appears in many cultures and spiritual beliefs as an emblem of unity and love. It also has important practical applications, like providing a framework to understand the evolution of species and how they respond to changing environmental conditions.

The first attempts to depict the biological world were built on categorizing organisms based on their physical and metabolic characteristics. These methods, which depend on the sampling of different parts of organisms or fragments of DNA have significantly increased the diversity of a tree of Life2. However the trees are mostly comprised of eukaryotes, and bacterial diversity remains vastly underrepresented3,4.

By avoiding the need for direct observation and experimentation genetic techniques have made it possible to represent the Tree of Life in a much more accurate way. Particularly, molecular methods allow us to build trees by using sequenced markers, such as the small subunit ribosomal gene.

Despite the massive expansion of the Tree of Life through genome sequencing, a large amount of biodiversity remains to be discovered. This is especially true of microorganisms, which are difficult to cultivate and are usually only found in a single specimen5. A recent study of all known genomes has produced a rough draft of the Tree of Life, including numerous bacteria and archaea that have not been isolated, and whose diversity is poorly understood6.

The expanded Tree of Life is particularly useful in assessing the diversity of an area, helping to determine if certain habitats require special protection. This information can be utilized in a variety of ways, such as identifying new drugs, combating diseases and improving crops. This information is also extremely useful to conservation efforts. It helps biologists determine the areas most likely to contain cryptic species with important metabolic functions that may be at risk from anthropogenic change. Although funding to safeguard biodiversity are vital however, the most effective method to preserve the world's biodiversity is for more people in developing countries to be equipped with the knowledge to act locally in order to promote conservation from within.

Phylogeny

A phylogeny (also called an evolutionary tree) depicts the relationships between different organisms. Utilizing molecular data as well as morphological similarities and distinctions or ontogeny (the course of development of an organism), scientists can build a phylogenetic tree that illustrates the evolution of taxonomic categories. Phylogeny is essential in understanding evolution, biodiversity and genetics.

A basic phylogenetic tree (see Figure PageIndex 10 Determines the relationship between organisms with similar characteristics and have evolved from an ancestor with common traits. These shared traits are either analogous or homologous. Homologous characteristics are identical in terms of their evolutionary paths. Analogous traits could appear similar but they don't share the same origins. Scientists organize similar traits into a grouping referred to as a the clade. For example, all of the organisms that make up a clade share the trait of having amniotic egg and evolved from a common ancestor that had these eggs. A phylogenetic tree is then constructed by connecting clades to identify the organisms which are the closest to each other.

For a more precise and precise phylogenetic tree scientists make use of molecular data from DNA or RNA to determine the connections between organisms. This information is more precise than morphological data and provides evidence of the evolution history of an organism or group. Researchers can use Molecular Data to determine the evolutionary age of organisms and determine the number of organisms that share the same ancestor.

Phylogenetic relationships can be affected by a number of factors, including the phenotypic plasticity. This is a kind of behavior that alters as a result of specific environmental conditions. This can cause a characteristic to appear more similar in one species than other species, which can obscure the phylogenetic signal. However, this problem can be solved through the use of techniques such as cladistics that incorporate a combination of homologous and analogous features into the tree.

In addition, phylogenetics helps determine the duration and rate of speciation. This information can assist conservation biologists decide the species they should safeguard from the threat of extinction. In the end, it's the preservation of phylogenetic diversity that will result in an ecosystem that is complete and balanced.

Evolutionary Theory

The central theme of evolution is that organisms develop different features over time based on their interactions with their surroundings. A variety of theories about evolution have been developed by a wide variety of scientists such as the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who envisioned an organism developing gradually according to its needs, the Swedish botanist Carolus Linnaeus (1707-1778) who developed modern hierarchical taxonomy, and Jean-Baptiste Lamarck (1744-1829) who suggested that the use or misuse of traits cause changes that can be passed on to offspring.


In the 1930s and 1940s, theories from various areas, including genetics, natural selection and particulate inheritance, came together to form a modern synthesis of evolution theory. This explains how evolution is triggered by the variations in genes within the population and how these variants alter over time due to natural selection. This model, which is known as genetic drift, mutation, gene flow, and sexual selection, is the foundation of modern evolutionary biology and is mathematically described.

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

Incorporating evolutionary thinking into all aspects of biology education could increase students' understanding of phylogeny as well as evolution. 에볼루션 바카라 사이트 by Grunspan and colleagues, for example, showed that teaching about the evidence for evolution helped students accept the concept of evolution in a college biology course. To learn more about how to teach about evolution, please see The Evolutionary Potential in All Areas of Biology and Thinking Evolutionarily A Framework for Infusing the Concept of Evolution into Life Sciences Education.

Evolution in Action

Traditionally, scientists have studied evolution by looking back--analyzing fossils, comparing species and observing living organisms. But evolution isn't a thing that happened in the past; it's an ongoing process, happening right now. The virus reinvents itself to avoid new medications and bacteria mutate to resist antibiotics. Animals adapt their behavior in the wake of the changing environment. The resulting changes are often visible.

It wasn't until the 1980s that biologists began realize that natural selection was also in action. The key is the fact that different traits confer a different rate of survival as well as reproduction, and may be passed down from generation to generation.

In the past, if a certain allele - the genetic sequence that determines color - was found in a group of organisms that interbred, it might become more common than any other allele. Over time, this would mean that the number of moths that have black pigmentation in a group may increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.

It is easier to see evolutionary change when an organism, like bacteria, has a high generation turnover. Since 1988, Richard Lenski, a biologist, has studied twelve populations of E.coli that are descended from a single strain. Samples of each population have been collected frequently and more than 500.000 generations of E.coli have been observed to have passed.

Lenski's research has revealed that a mutation can profoundly alter the rate at the rate at which a population reproduces, and consequently the rate at which it alters. It also demonstrates that evolution is slow-moving, a fact that many find difficult to accept.

Another example of microevolution is the way mosquito genes that confer resistance to pesticides appear more frequently in areas where insecticides are employed. This is because pesticides cause an exclusive pressure that 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 adjusting. Understanding evolution will aid you in making better decisions about the future of the planet and its inhabitants.