The Academy's Evolution Site
Biological evolution is a central concept in biology. The Academies are committed to helping those who are interested in the sciences understand evolution theory and how it can be applied in all areas of scientific research.
This site offers a variety of tools for teachers, students as well as general readers about 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, symbolizes the interconnectedness of all life. It is a symbol of love and harmony in a variety of cultures. It has many practical applications in addition to providing a framework to understand 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 were distinguished by physical and metabolic characteristics1. These methods, which relied on the sampling of various parts of living organisms or short fragments of their DNA, significantly increased the variety that could be represented in a tree of life2. However, these trees are largely made up of eukaryotes. Bacterial diversity is not represented in a large way3,4.
Genetic techniques have significantly expanded our ability to represent the Tree of Life by circumventing the requirement for direct observation and experimentation. We can construct trees using molecular methods, such as the small-subunit ribosomal gene.
Despite the massive growth of the Tree of Life through genome sequencing, much biodiversity still remains to be discovered. This is especially true of microorganisms, which are difficult to cultivate and are typically only found in a single specimen5. mouse click the up coming post of all genomes resulted in an initial draft of the Tree of Life. This includes a large number of archaea, bacteria and other organisms that haven't yet been identified or their diversity is not well understood6.
The expanded Tree of Life can be used to evaluate the biodiversity of a specific area and determine if specific habitats require special protection. The information is useful in many ways, including finding new drugs, battling diseases and improving the quality of crops. This information is also extremely beneficial for conservation efforts. It helps biologists discover areas that are likely to be home to cryptic species, which may have important metabolic functions and be vulnerable to changes caused by humans. While conservation funds are important, the most effective method to protect the biodiversity of the world is to equip more people in developing nations with the necessary knowledge to take action locally and encourage conservation.
Phylogeny
A phylogeny (also called an evolutionary tree) shows the relationships between organisms. Scientists can create a phylogenetic chart that shows the evolution of taxonomic groups using molecular data and morphological similarities or differences. The role of phylogeny is crucial in understanding biodiversity, genetics and evolution.
A basic phylogenetic tree (see Figure PageIndex 10 Identifies the relationships between organisms that have similar characteristics and have evolved from a common ancestor. These shared traits could be either homologous or analogous. Homologous traits are identical in their underlying evolutionary path, while analogous traits look similar, but do not share the identical origins. Scientists combine similar traits into a grouping referred to as a clade. For instance, all the species in a clade share the trait of having amniotic egg and evolved from a common ancestor which had these eggs. The clades are then linked to form a phylogenetic branch that can identify organisms that have the closest connection to each other.
To create a more thorough and accurate phylogenetic tree scientists make use of molecular data from DNA or RNA to determine the connections between organisms. This information is more precise and provides evidence of the evolution history of an organism. Researchers can use Molecular Data to determine the age of evolution of organisms and determine how many organisms have an ancestor common to all.
The phylogenetic relationship can be affected by a variety of factors that include the phenotypic plasticity. This is a kind of behavior that changes as a result of specific environmental conditions. This can cause a trait to appear more like a species another, clouding the phylogenetic signal. This problem can be mitigated by using cladistics. This is a method that incorporates a combination of homologous and analogous traits in the tree.
Furthermore, phylogenetics may help predict the duration and rate of speciation. This information can help conservation biologists decide the species they should safeguard from the threat of extinction. In the end, it's the conservation of phylogenetic diversity that will result in an ecosystem that is balanced and complete.
Evolutionary Theory
The main idea behind evolution is that organisms develop different features over time based on their interactions with their surroundings. Several theories of evolutionary change have been proposed by a wide range of scientists such as the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who proposed that a living organism develop slowly according to its requirements, the Swedish botanist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical taxonomy, as well as Jean-Baptiste Lamarck (1744-1829) who suggested that the use or misuse of traits causes changes that can be passed on to offspring.
In the 1930s and 1940s, ideas from a variety of fields--including genetics, natural selection, and particulate inheritance--came together to create the modern evolutionary theory synthesis that explains how evolution happens through the variation of genes within a population, and how these variants change over time due to natural selection. This model, which incorporates mutations, genetic drift, gene flow and sexual selection, can be mathematically described mathematically.
Recent advances in the field of evolutionary developmental biology have shown how variations can be introduced to a species by mutations, genetic drift or reshuffling of genes in sexual reproduction and the movement between populations. These processes, along with other ones like directional selection and genetic erosion (changes in the frequency of a genotype over time) can result in evolution, which is defined by changes in the genome of the species over time, and the change in phenotype as time passes (the expression of the genotype in an individual).
Students can better understand the concept of phylogeny by using evolutionary thinking in all aspects of biology. In a study by Grunspan and colleagues. It was found that teaching students about the evidence for evolution increased their acceptance of evolution during the course of a college biology. To find out more about how to teach about evolution, read The Evolutionary Potential in All Areas of Biology and Thinking Evolutionarily A Framework for Infusing the Concept of 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. Evolution is not a distant event, but an ongoing process that continues to be observed today. The virus reinvents itself to avoid new drugs and bacteria evolve to resist antibiotics. Animals alter their behavior because of the changing environment. The resulting changes are often visible.
It wasn't until the late 1980s that biologists began to realize that natural selection was also in action. The reason is that different traits confer different rates of survival and reproduction (differential fitness), and can be passed from one generation to the next.
In the past, when one particular allele - the genetic sequence that controls coloration - was present in a population of interbreeding species, it could quickly become more common than all other alleles. As time passes, this could mean that the number of moths that have black pigmentation may 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 been tracking twelve populations of E.coli that descend from a single strain. Samples of each population have been taken frequently and more than 500.000 generations of E.coli have passed.
Lenski's research has revealed that mutations can alter the rate of change and the effectiveness of a population's reproduction. It also shows evolution takes time, which is hard for some to accept.
Microevolution is also evident in the fact that mosquito genes for resistance to pesticides are more common in populations where insecticides have been used. This is due to pesticides causing a selective pressure which favors those with resistant genotypes.
The rapidity of evolution has led to a growing appreciation of its importance, especially in a world shaped largely by human activity. This includes pollution, climate change, and habitat loss that prevents many species from adapting. Understanding the evolution process can help us make smarter decisions regarding the future of our planet, and the lives of its inhabitants.