The Academy's Evolution Site

Biological evolution is one of the most fundamental concepts in biology. The Academies are committed to helping those who are interested in science learn about the theory of evolution and how it is permeated across all areas of scientific research.

This site provides a wide range of resources for students, teachers and general readers of evolution. It contains key video clips from NOVA and WGBH produced 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 can be used in many practical ways in addition to providing a framework for understanding the history of species, and how they react to changing environmental conditions.

The first attempts at depicting the world of biology focused on separating species into distinct categories that were distinguished by their physical and metabolic characteristics1. These methods are based on the collection of various parts of organisms, or DNA fragments, have greatly increased the diversity of a tree of Life2. The trees are mostly composed of eukaryotes, while bacterial diversity is vastly underrepresented3,4.

By avoiding the need 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 construct trees using sequenced markers like the small subunit ribosomal gene.

The Tree of Life has been dramatically expanded through genome sequencing. However there is still a lot of biodiversity to be discovered. This is particularly true of microorganisms that are difficult to cultivate and are usually only represented in a single specimen5. Recent analysis of all genomes has produced an initial draft of a Tree of Life. This includes a variety of archaea, bacteria and other organisms that haven't yet been isolated, or their diversity is not well understood6.

This expanded Tree of Life can be used to evaluate the biodiversity of a specific area and determine if particular habitats require special protection. This information can be used in a variety of ways, including finding new drugs, fighting diseases and enhancing crops. It is also useful for conservation efforts. It can help biologists identify the areas that are most likely to contain cryptic species with potentially important metabolic functions that may be at risk from anthropogenic change. Although funds to protect biodiversity are essential but the most effective way to protect the world's biodiversity is for more people in developing countries to be equipped with the knowledge to act locally to promote conservation from within.

Phylogeny

A phylogeny (also known as an evolutionary tree) illustrates the relationship between different organisms. Scientists can build an phylogenetic chart which shows the evolutionary relationships between taxonomic groups using molecular data and morphological differences or similarities. The role of phylogeny is crucial in understanding the relationship between genetics, biodiversity and evolution.

A basic phylogenetic tree (see Figure PageIndex 10 Identifies the relationships between organisms that have similar characteristics and have evolved from an ancestor that shared traits. These shared traits could be analogous, or homologous. Homologous traits are the same in terms of their evolutionary paths. Analogous traits could appear similar however they do not share the same origins. Scientists group similar traits together into a grouping called a clade. For instance, all of the species in a clade share the characteristic of having amniotic egg and evolved from a common ancestor which had eggs. The clades are then connected to create a phylogenetic tree to determine which organisms have the closest relationship.

For 에볼루션 무료체험 detailed and accurate phylogenetic tree, scientists use molecular data from DNA or RNA to determine the connections between organisms. This information is more precise and gives evidence of the evolutionary history of an organism. Molecular data allows researchers to determine the number of organisms that share an ancestor common to them and estimate their evolutionary age.

The phylogenetic relationships of organisms are influenced by many factors, including phenotypic plasticity a kind of behavior that alters in response to unique environmental conditions. This can cause a trait to appear more like a species another, obscuring the phylogenetic signal. However, this problem can be solved through the use of methods such as cladistics that combine analogous and homologous features into the tree.

In addition, phylogenetics can help predict the time and pace of speciation. This information can assist conservation biologists make decisions about the species they should safeguard from extinction. In the end, it is the conservation of phylogenetic variety that will lead to an ecosystem that is complete and balanced.

Evolutionary Theory

The fundamental concept in evolution is that organisms change over time as a result of their interactions with their environment. Many scientists have come up with theories of evolution, such as the Islamic naturalist Nasir al-Din al-Tusi (1201-274) who believed that a living thing would evolve according to its individual requirements and needs, the Swedish taxonomist Carolus Linnaeus (1707-1778) who conceived the modern taxonomy system that is hierarchical and Jean-Baptiste Lamarck (1844-1829), who believed that the use or absence of traits can lead to changes that are passed on to the next generation.

In the 1930s & 1940s, ideas from different fields, such as genetics, natural selection and particulate inheritance, came together to create a modern evolutionary theory. This explains how evolution occurs by the variations in genes within a population and how these variations change over time as a result of natural selection. This model, which includes genetic drift, mutations as well as gene flow and sexual selection can be mathematically described mathematically.

Recent developments in the field of evolutionary developmental biology have revealed that variation can be introduced into a species via mutation, genetic drift and reshuffling of genes during sexual reproduction, and also by migration between populations. These processes, as well as other ones like directional selection and genetic erosion (changes in the frequency of an individual's genotype over time) can result in evolution which is defined by change in the genome of the species over time, and the change in phenotype as time passes (the expression of that genotype in the individual).

Incorporating evolutionary thinking into all aspects of biology education can increase student understanding of the concepts of phylogeny as well as evolution. In a recent study conducted by Grunspan and co., it was shown that teaching students about the evidence for evolution boosted their understanding of evolution in an undergraduate biology course. For more information about how to teach evolution read The Evolutionary Potential in All Areas of Biology or Thinking Evolutionarily: a Framework for Infusing Evolution into Life Sciences Education.

Evolution in Action

Scientists have traditionally looked at evolution through the past, studying fossils, and comparing species. They also study living organisms. Evolution is not a distant event; it is an ongoing process. Viruses evolve to stay away from new antibiotics and bacteria transform to resist antibiotics. Animals alter their behavior in the wake of a changing environment. The changes that occur are often apparent.


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

In the past, if one particular allele - the genetic sequence that defines color in a group of interbreeding organisms, it could quickly become more prevalent than other alleles. As time passes, this could mean that the number of moths that have black pigmentation in a population 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 evolution when the species, like 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 are taken regularly and over fifty thousand generations have passed.

Lenski's research has revealed that a mutation can dramatically alter the efficiency with which a population reproduces--and so the rate at which it changes. It also demonstrates that evolution is slow-moving, a fact that some find difficult to accept.

Another example of microevolution is the way mosquito genes for resistance to pesticides are more prevalent in populations where insecticides are employed. This is because the use of pesticides creates a selective pressure that favors those with resistant genotypes.

The rapid pace of evolution taking place has led to a growing awareness of its significance in a world that is shaped by human activity, including climate change, pollution and the loss of habitats which prevent the species from adapting. Understanding the evolution process will help us make better decisions regarding the future of our planet, and the lives of its inhabitants.