The Academy's Evolution Site
Biology is a key concept in biology. The Academies are committed to helping those who are interested in science to comprehend the evolution theory and how it is permeated throughout all fields of scientific research.
This site provides a wide range of sources for teachers, students as well as general readers about evolution. It includes key video clips from NOVA and the WGBH-produced science programs on DVD.
Tree of Life
The Tree of Life, an ancient symbol, symbolizes the interconnectedness of all life. It is an emblem of love and unity across many cultures. It also has practical uses, like providing a framework for understanding the evolution of species and how they react to changing environmental conditions.
Early attempts to represent the world of biology were built on categorizing organisms based on their physical and metabolic characteristics. These methods, which are based on the sampling of different parts of organisms or short DNA fragments, 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.
In avoiding the necessity of direct observation and experimentation, genetic techniques have made it possible to depict 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 dramatic growth of the Tree of Life through genome sequencing, a lot of biodiversity is waiting to be discovered. This is especially true of microorganisms, which can be difficult to cultivate and are typically only represented in a single sample5. A recent analysis of all genomes known to date has produced a rough draft of the Tree of Life, including a large number of archaea and bacteria that are not isolated and their diversity is not fully understood6.
This expanded Tree of Life is particularly beneficial in assessing the biodiversity of an area, helping to determine if specific habitats require protection. This information can be used in a variety of ways, including identifying new drugs, combating diseases and improving crops. This information is also extremely beneficial to conservation efforts. It can aid biologists in identifying those areas that are most likely contain cryptic species with potentially important metabolic functions that could be at risk of anthropogenic changes. Although funds to protect biodiversity are essential, ultimately the best way to ensure the preservation of biodiversity around the world is for more people living in developing countries to be empowered with the knowledge to act locally to promote conservation from within.
Phylogeny
A phylogeny, also known as an evolutionary tree, illustrates the relationships between various groups of organisms. Scientists can construct a phylogenetic chart that shows the evolutionary relationship of taxonomic groups based on molecular data and morphological differences or similarities. The phylogeny of a tree plays an important role in understanding biodiversity, genetics and evolution.
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 could be either analogous or homologous. Homologous traits are identical in their evolutionary roots, while analogous traits look like they do, but don't have the same ancestors. Scientists group similar traits into a grouping known as a the clade. For instance, all the organisms in a clade share the trait of having amniotic eggs and evolved from a common ancestor which had these eggs. The clades are then connected to form a phylogenetic branch that can identify organisms that have the closest relationship to.
For a more precise and accurate phylogenetic tree, scientists use molecular data from DNA or RNA to establish the connections between organisms. This information is more precise and gives evidence of the evolution of an organism. Molecular data allows researchers to identify the number of species that have the same ancestor and estimate their evolutionary age.
The phylogenetic relationships between organisms can be affected by a variety of factors, including phenotypic flexibility, an aspect 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 reduced by the use of techniques such as cladistics which include a mix of homologous and analogous features into the tree.
Furthermore, phylogenetics may aid in predicting the time and pace of speciation. This information can aid conservation biologists in making decisions about which species to safeguard from disappearance. In the end, it's the preservation of phylogenetic diversity which will result in an ecologically balanced and complete ecosystem.
Evolutionary Theory
The main idea behind evolution is that organisms develop various characteristics over time as a result of their interactions with their surroundings. Many scientists have proposed theories of evolution, such as the Islamic naturalist Nasir al-Din al-Tusi (1201-274) who believed that an organism would evolve according to its own 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 suggested that the use or absence of traits can cause changes that are passed on to the next generation.
In the 1930s and 1940s, concepts from various fields, including genetics, natural selection and particulate inheritance - came together to create the modern synthesis of evolutionary theory that explains how evolution happens through the variation of genes within a population, and how those variations change over time as a result of natural selection. This model, called genetic drift, mutation, gene flow, and sexual selection, is a key element of current evolutionary biology, and is mathematically described.
Read More Listed here in evolutionary developmental biology have shown how variations can be introduced to a species via genetic drift, mutations and reshuffling of genes during sexual reproduction and the movement between populations. These processes, as well as other ones like directionally-selected selection and erosion of genes (changes in frequency of genotypes over time) can lead to evolution. Evolution is defined as changes in the genome over time, as well as changes in the phenotype (the expression of genotypes in an individual).
Students can better understand phylogeny by incorporating evolutionary thinking in all areas of biology. In a recent study conducted by Grunspan et al. It was demonstrated that teaching students about the evidence for evolution boosted their understanding of evolution in the course of a college biology. For more details on how to teach evolution, see The Evolutionary Potential in all Areas of Biology or Thinking Evolutionarily A Framework for Integrating Evolution into Life Sciences Education.
Evolution in Action
Scientists have studied evolution by looking in the past, studying fossils, and comparing species. They also observe living organisms. Evolution isn't a flims event, but an ongoing process. Bacteria evolve and resist antibiotics, viruses re-invent themselves and elude new medications and animals alter their behavior in response to the changing climate. The results are usually evident.
But it wasn't until the late 1980s that biologists understood that natural selection could be observed in action as well. The key to this is that different traits confer a different rate of survival and reproduction, and they can be passed down from generation to generation.
In the past, if one allele - the genetic sequence that determines colour was found in a group of organisms that interbred, it might become more common than other allele. As time passes, this could mean that the number of moths that have black pigmentation in a population could 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 the biologist Richard Lenski has been tracking twelve populations of E. bacteria that descend from a single strain; samples of each population are taken regularly, and over 50,000 generations have now been observed.
Lenski's research has demonstrated that mutations can alter the rate at which change occurs and the efficiency at which a population reproduces. It also shows evolution takes time, a fact that is difficult for some to accept.
Another example of microevolution is how mosquito genes that confer resistance to pesticides are more prevalent in areas where insecticides are used. Pesticides create a selective pressure which favors individuals who have resistant genotypes.
The rapidity of evolution has led to an increasing awareness of its significance especially in a planet shaped largely by human activity. This includes the effects of climate change, pollution and habitat loss that prevents many species from adapting. Understanding evolution will aid you in making better decisions regarding the future of the planet and its inhabitants.
