The Academy's Evolution Site
Biology is a key concept in biology. The Academies have been for a long time involved in helping those interested in science comprehend the concept of evolution and how it permeates all areas of scientific exploration.
This site offers a variety of resources for teachers, students, and general readers on evolution. It also includes important video clips from NOVA and WGBH produced science programs on DVD.
Tree of Life
The Tree of Life, an ancient symbol, represents the interconnectedness of all life. It is used in many cultures and spiritual beliefs as symbolizing unity and love. It also has practical applications, such as providing a framework for understanding the evolution of species and how they respond to changes in the environment.
Early attempts to describe the biological world were built on categorizing organisms based on their physical and metabolic characteristics. These methods depend on the sampling of different parts of organisms or DNA fragments, have significantly increased the diversity of a tree of Life2. However the trees are mostly composed of eukaryotes; bacterial diversity is not represented in a large way3,4.
By avoiding the necessity for direct observation and experimentation genetic techniques have allowed us to represent the Tree of Life in a more precise manner. We can create trees using molecular methods, such as the small-subunit ribosomal gene.
Despite the rapid expansion of the Tree of Life through genome sequencing, a lot of biodiversity is waiting to be discovered. This is especially relevant to microorganisms that are difficult to cultivate and which are usually only found in a single specimen5. A recent analysis of all genomes resulted in an unfinished draft of the Tree of Life. This includes a large number of archaea, bacteria and other organisms that have not yet been isolated, or the diversity of which is not thoroughly understood6.
This expanded Tree of Life can be used to evaluate the biodiversity of a specific region and determine if certain habitats need special protection. This information can be used in a variety of ways, including finding new drugs, battling diseases and enhancing crops. It is also useful for conservation efforts. It helps biologists discover areas most likely to be home to cryptic species, which could have important metabolic functions and are susceptible to human-induced change. Although funds to protect biodiversity are crucial however, the most effective method to preserve the world's biodiversity is for more people living in developing countries to be equipped with the knowledge to take action locally to encourage conservation from within.
Phylogeny
A phylogeny, also called an evolutionary tree, illustrates the relationships between various groups of organisms. Scientists can construct an phylogenetic chart which shows the evolutionary relationships between taxonomic groups using molecular data and morphological differences or similarities. Phylogeny is essential in understanding biodiversity, evolution and genetics.
A basic phylogenetic Tree (see Figure PageIndex 10 ) identifies the relationships between organisms with similar traits that have evolved from common ancestral. These shared traits can be either homologous or analogous. Homologous characteristics are identical in terms of their evolutionary path. Analogous traits may look similar however they do not share the same origins. Scientists group similar traits into a grouping called a Clade. For instance, all the organisms that make up a clade share the characteristic of having amniotic egg and evolved from a common ancestor which had eggs. The clades then join to create a phylogenetic tree to identify organisms that have the closest connection to each other.
Scientists make use of DNA or RNA molecular data to build a phylogenetic chart that is more precise and detailed. This information is more precise and provides evidence of the evolution of an organism. Researchers can utilize Molecular Data to estimate the evolutionary age of living organisms and discover the number of organisms that share an ancestor common to all.
Phylogenetic relationships can be affected by a number of factors that include the phenotypic plasticity. This is a type of behavior that alters as a result of particular environmental conditions. This can cause a particular trait to appear more similar to one species than another, obscuring the phylogenetic signal. However, this problem can be cured by the use of techniques such as cladistics that incorporate a combination of similar and homologous traits into the tree.
In addition, phylogenetics helps determine the duration and speed at which speciation occurs. This information can assist conservation biologists make decisions about the species they should safeguard from the threat of extinction. In the end, it's the preservation of phylogenetic diversity which will create an ecosystem that is balanced and complete.
Evolutionary Theory
The fundamental concept in evolution is that organisms alter over time because of their interactions with their environment. Many theories of evolution have been developed by a wide range of scientists, including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who believed that an organism would evolve gradually according to its needs, the Swedish botanist Carolus Linnaeus (1707-1778) who conceived modern hierarchical taxonomy, and Jean-Baptiste Lamarck (1744-1829) who suggested that the use or non-use of traits causes changes that can be passed on to offspring.
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 describes how evolution is triggered by the variations in genes within a population and how these variations alter over time due to natural selection. This model, which encompasses genetic drift, mutations as well as gene flow and sexual selection can be mathematically described.
Recent developments in the field of evolutionary developmental biology have demonstrated that variations can be introduced into a species via mutation, genetic drift and reshuffling of genes during sexual reproduction, as well as by migration between populations. These processes, as well as others such as directional selection or genetic erosion (changes in the frequency of an individual's genotype over time) can lead to evolution that is defined as changes 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 by using evolutionary thinking throughout all areas of biology. 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-level 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 Evolution into Life Sciences Education.
Evolution in Action
Scientists have traditionally studied evolution through looking back in the past--analyzing fossils and comparing species. They also observe living organisms. But evolution isn't a thing that happened in the past, it's an ongoing process that is taking place today. Bacteria transform and resist antibiotics, viruses reinvent themselves and are able to evade new medications and animals alter their behavior in response to the changing environment. The results are often evident.
It wasn't until the late 1980s that biologists began to realize that natural selection was also in play. The main reason is that different traits result in the ability to survive at different rates and reproduction, and can be passed down from generation to generation.
In the past, if an allele - the genetic sequence that determines color - was found in a group of organisms that interbred, it might become more prevalent than any other allele. As time passes, that could mean that the number of black moths in a particular population could rise. 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 the species, like bacteria, has a high generation turnover. Since 1988, Richard Lenski, a biologist, has studied twelve populations of E.coli that descend from one strain. The samples of each population were taken frequently and more than 50,000 generations of E.coli have passed.
Lenski's work has demonstrated that mutations can drastically alter the speed at which a population reproduces--and so the rate at which it evolves. It also shows that evolution takes time, a fact that some people are unable to accept.
Another example of microevolution is that mosquito genes for resistance to pesticides appear more frequently in populations where insecticides are used. 에볼루션코리아 create an exclusive pressure that favors those with resistant genotypes.
The speed at which evolution takes place has led to a growing recognition 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 the evolution process will assist you in making better choices about the future of our planet and its inhabitants.