The Academy's Evolution Site
Biology is a key concept in biology. The Academies are committed to helping those interested in science understand evolution theory and how it is incorporated throughout all fields of scientific research.
This site provides teachers, students and general readers with a variety of learning resources on evolution. It includes key video clip from NOVA and WGBH produced science programs on DVD.
Tree of Life
The Tree of Life is an ancient symbol that symbolizes the interconnectedness of life. It appears in many religions and cultures as symbolizing unity and love. It can be used in many practical ways in addition to providing a framework to understand the evolution of species and how they react to changing environmental conditions.
The earliest attempts to depict the world of biology focused on categorizing species into distinct categories that were identified by their physical and metabolic characteristics1. These methods, which relied on sampling of different parts of living organisms or sequences of short fragments of their DNA greatly increased the variety of organisms that could be included in the tree of life2. However, 에볼루션 바카라 are largely comprised of eukaryotes, and bacterial diversity is not represented in a large way3,4.
In avoiding the necessity of direct observation and experimentation genetic techniques have enabled us to represent the Tree of Life in a more precise way. We can construct trees using molecular techniques such as the small subunit ribosomal gene.
Despite the rapid growth of the Tree of Life through genome sequencing, a large amount of biodiversity awaits discovery. This is particularly true for microorganisms that are difficult to cultivate and are often only found in a single sample5. A recent analysis of all known genomes has produced a rough draft version of the Tree of Life, including many archaea and bacteria that have not been isolated, and whose diversity is poorly understood6.
This expanded Tree of Life is particularly beneficial in assessing the biodiversity of an area, which can help to determine whether specific habitats require protection. This information can be used in a variety of ways, such as finding new drugs, battling diseases and improving the quality of crops. This information is also extremely beneficial for conservation efforts. It can aid biologists in identifying the areas that are most likely to contain cryptic species with potentially important metabolic functions that may be at risk from anthropogenic change. While funds to protect biodiversity are important, the most effective method to preserve the biodiversity of the world is to equip more people in developing countries with the necessary knowledge to act locally and support conservation.
Phylogeny
A phylogeny is also known as an evolutionary tree, reveals the connections between different groups of organisms. By using molecular information, morphological similarities and differences, or ontogeny (the course of development of an organism) scientists can create a phylogenetic tree that illustrates the evolution of taxonomic categories. The phylogeny of a tree plays an important role in understanding the relationship between genetics, biodiversity and evolution.
A basic phylogenetic Tree (see Figure PageIndex 10 Determines the relationship between organisms with similar traits and have evolved from an ancestor that shared traits. These shared traits may be analogous or homologous. Homologous traits are the same in terms of their evolutionary journey. Analogous traits could appear similar, but they do not share the same origins. Scientists group similar traits into a grouping called a the clade. For example, all of the organisms that make up a clade share the trait of having amniotic eggs. They evolved from a common ancestor which had these eggs. A phylogenetic tree is then constructed by connecting clades to determine the organisms that are most closely related to one another.
Scientists use DNA or RNA molecular information to create a phylogenetic chart that is more precise and precise. This information is more precise and provides evidence of the evolutionary history of an organism. Researchers can use Molecular Data to calculate the age of evolution of living organisms and discover how many organisms have an ancestor common to all.
The phylogenetic relationships between organisms are influenced by many factors, including phenotypic plasticity an aspect of behavior that changes in response to unique environmental conditions. This can cause a particular trait to appear more like a species another, clouding the phylogenetic signal. However, this problem can be cured by the use of methods like cladistics, which incorporate a combination of analogous and homologous features into the tree.
Additionally, phylogenetics can help determine the duration and speed at which speciation occurs. This information can help conservation biologists make decisions about which species to protect from the threat of extinction. It is ultimately the preservation of phylogenetic diversity which will create an ecologically balanced and complete ecosystem.
Evolutionary Theory
The central theme of evolution is that organisms acquire distinct characteristics over time due to their interactions with their environments. Several theories of evolutionary change have been proposed by a wide variety of scientists including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who believed that an organism would evolve slowly according to its requirements and needs, the Swedish botanist Carolus Linnaeus (1707-1778) who developed the modern hierarchical taxonomy Jean-Baptiste Lamarck (1744-1829) who suggested that the use or misuse of traits can cause changes that could be passed onto offspring.
In the 1930s & 1940s, theories from various areas, including genetics, natural selection, and particulate inheritance, were brought together to form a contemporary synthesis of evolution theory. This describes how evolution is triggered by the variations in genes within the population, and how these variations change over time as a result of natural selection. This model, which incorporates genetic drift, mutations, gene flow and sexual selection, can be mathematically described.
Recent discoveries in evolutionary developmental biology have demonstrated how variation can be introduced to a species through genetic drift, mutations and reshuffling of genes during sexual reproduction and the movement between populations. These processes, in conjunction with other ones like directionally-selected selection and erosion of genes (changes in frequency of genotypes over time), can lead towards evolution. Evolution is defined as changes in the genome over time as well as changes in phenotype (the expression of genotypes within individuals).
Incorporating evolutionary thinking into all aspects of biology education can increase students' understanding of phylogeny and evolution. A recent study by Grunspan and colleagues, for example, showed that teaching about the evidence supporting evolution increased students' acceptance of evolution in a college biology course. For more information on how to teach about evolution, please read The Evolutionary Potential of 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 through looking back, studying fossils, comparing species, and studying living organisms. Evolution is not a past event, but an ongoing process that continues to be observed today. Viruses evolve to stay away from new drugs and bacteria evolve to resist antibiotics. Animals adapt their behavior because of a changing world. The resulting changes are often evident.
It wasn't until the 1980s that biologists began realize that natural selection was at work. The key is the fact that different traits result in an individual rate of survival and reproduction, and they can be passed on from one generation to another.
In the past, if an allele - the genetic sequence that determines color - was found in a group of organisms that interbred, it could become more common than other allele. 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.
Observing evolutionary change in action is much easier when a species has a fast generation turnover such as bacteria. Since 1988, Richard Lenski, a biologist, has tracked twelve populations of E.coli that are descended from one strain. Samples of each population have been collected regularly and more than 500.000 generations of E.coli have passed.
Lenski's research has shown that a mutation can dramatically alter the efficiency with which a population reproduces--and so, the rate at which it alters. It also shows evolution takes time, something that is hard for some to accept.
Microevolution is also evident in the fact that mosquito genes for resistance to pesticides are more prevalent in populations that have used insecticides. This is due to pesticides causing an exclusive pressure that favors those with 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 that hinder many species from adjusting. Understanding the evolution process can help us make smarter choices about the future of our planet, and the life of its inhabitants.