The Academy's Evolution Site

Biological evolution is a central concept in biology. The Academies are committed to helping those interested in science to understand evolution theory and how it is permeated across all areas of scientific research.

This site provides teachers, students and general readers with a range of educational resources on evolution. It includes key video clip 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 used in many cultures and spiritual beliefs as an emblem of unity and love. It also has practical applications, such as providing a framework for understanding the history of species and how they respond to changes in environmental conditions.

The earliest attempts to depict the biological world focused on the classification of organisms into distinct categories that had been distinguished by their physical and metabolic characteristics1. These methods, which are based on the sampling of different parts of organisms or DNA fragments, have significantly increased the diversity of a tree of Life2. These trees are mostly populated by eukaryotes, and the diversity of bacterial species is greatly underrepresented3,4.

In avoiding the necessity of direct experimentation and observation, genetic techniques have allowed us to represent the Tree of Life in a more precise way. In particular, molecular methods allow us to build 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 especially true of microorganisms, which are difficult to cultivate and are typically only present in a single specimen5. Recent analysis of all genomes has produced an initial draft of a Tree of Life. This includes a large number of archaea, bacteria and other organisms that have not yet been identified or their diversity is not well understood6.

This 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 range of ways, from identifying new medicines to combating disease to enhancing the quality of crops. The information is also incredibly useful for conservation efforts. It helps biologists determine those areas that are most likely contain cryptic species with potentially important metabolic functions that may be vulnerable to anthropogenic change. While funds to safeguard biodiversity are vital however, the most effective method to protect the world's biodiversity is for more people in developing countries to be empowered with the necessary knowledge to take action locally to encourage conservation from within.

Phylogeny

A phylogeny is also known as an evolutionary tree, illustrates the connections between various groups of organisms. Scientists can build a phylogenetic chart that shows the evolutionary relationship of taxonomic groups using molecular data and 에볼루션 바카라 무료 morphological similarities or differences. The concept of phylogeny is fundamental to understanding biodiversity, evolution and genetics.

A basic phylogenetic Tree (see Figure PageIndex 10 ) is a method of identifying the relationships between organisms that share similar traits that have evolved from common ancestors. These shared traits may be analogous or homologous. Homologous traits share their underlying evolutionary path while analogous traits appear similar but do not have the same ancestors. Scientists group similar traits into a grouping referred to as a Clade. Every organism in a group have a common trait, such as amniotic egg production. They all derived from an ancestor who had these eggs. The clades then join to form a phylogenetic branch to identify organisms that have the closest connection to each other.

For a more precise and accurate phylogenetic tree scientists use 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 evolutionary background of an organism or group. Researchers can utilize Molecular Data to calculate the evolutionary age of living organisms and discover how many species have an ancestor common to all.

The phylogenetic relationships of a species can be affected by a number of factors that include the phenomenon of phenotypicplasticity. This is a kind of behaviour that can change in response to particular environmental conditions. This can cause a particular trait to appear more like a species other species, which can obscure the phylogenetic signal. This problem can be mitigated by using cladistics. This is a method that incorporates the combination of homologous and analogous features in the tree.

Additionally, phylogenetics can aid in predicting the time and pace of speciation. This information can aid conservation biologists in making decisions about which species to protect from extinction. It is ultimately the preservation of phylogenetic diversity which will result in an ecosystem that is complete and balanced.

Evolutionary Theory

The fundamental concept in evolution is that organisms change over time due to 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 an organism could evolve according to its own needs, the Swedish taxonomist Carolus Linnaeus (1707-1778) who developed the modern hierarchical system of taxonomy as well as Jean-Baptiste Lamarck (1844-1829), who believed that the use or absence of traits can lead to changes that are passed on to the

In the 1930s & 1940s, ideas from different fields, such as genetics, natural selection, and particulate inheritance, were brought together to form a contemporary theorizing of evolution. This describes how evolution is triggered by the variation in genes within a population and how these variants change with time due to natural selection. This model, which is known as genetic drift or mutation, gene flow and sexual selection, is a cornerstone of the current 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 via genetic drift, mutation, and reshuffling of genes in sexual reproduction, and also through 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 lead to evolution that is defined as 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 improve students' understanding of phylogeny and evolutionary. A recent study conducted by Grunspan and colleagues, for example, showed that teaching about the evidence that supports evolution increased students' acceptance of evolution in a college biology class. For more details on how to teach about evolution, see The Evolutionary Potency in All Areas of Biology or Thinking Evolutionarily: a Framework for Infusing Evolution into Life Sciences Education.

Evolution in Action

Traditionally scientists have studied evolution through looking back--analyzing fossils, comparing species, and observing living organisms. However, evolution isn't something that happened in the past. It's an ongoing process, taking place right now. Viruses evolve to stay away from new antibiotics and bacteria transform to resist antibiotics. Animals alter their behavior because of a changing world. The changes that result are often evident.

It wasn't until late 1980s that biologists began to realize that natural selection was also in play. The key to this is that different traits result in a different rate of survival and reproduction, and can be passed on from one generation to another.

In the past, if one particular allele - the genetic sequence that determines coloration--appeared in a population of interbreeding organisms, it might quickly become more prevalent than all other alleles. In time, this could mean that the number of moths sporting 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 an organism, like bacteria, has a rapid generation turnover. Since 1988, Richard Lenski, a biologist, has tracked twelve populations of E.coli that are descended from one strain. Samples from each population have been collected regularly, and more than 50,000 generations of E.coli have been observed to have passed.

Lenski's work has demonstrated that mutations can drastically alter 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.

Microevolution can be observed in the fact that mosquito genes for resistance to pesticides are more prevalent in areas where insecticides have been used. This is due to pesticides causing a selective pressure which favors individuals who have resistant genotypes.

The rapid pace at which evolution takes place has led to a growing recognition of its importance in a world shaped by human activity--including climate change, pollution and the loss of habitats that prevent the species from adapting. Understanding the evolution process can help us make smarter choices about the future of our planet and the lives of its inhabitants.