The Academy's Evolution Site
Biology is a key concept in biology. The Academies are involved in helping those interested in science comprehend the evolution theory and how it is incorporated across all areas of scientific research.
This site provides teachers, students and general readers with a variety of educational resources on evolution. It contains key video clips from NOVA and WGBH produced science programs on DVD.
Tree of Life
The Tree of Life is an ancient symbol of the interconnectedness of all life. It is used in many religions and cultures as a symbol of unity and love. It has many practical applications as well, including providing a framework for understanding the history of species and how they respond to changes in environmental conditions.
Early attempts to describe the world of biology were based on categorizing organisms based on their physical and metabolic characteristics. These methods, which rely on sampling of different parts of living organisms or on small fragments of their DNA significantly expanded the diversity that could be represented in the tree of life2. However, these trees are largely comprised of eukaryotes, and bacterial diversity is still largely unrepresented3,4.
Genetic techniques have significantly expanded our ability to depict the Tree of Life by circumventing the requirement for direct observation and experimentation. Trees can be constructed using molecular techniques like the small-subunit ribosomal gene.
Despite the massive growth of the Tree of Life through genome sequencing, a lot of biodiversity is waiting to be discovered. This is particularly true of microorganisms, which can be difficult to cultivate and are often only found in a single specimen5. A recent study of all known genomes has created a rough draft of the Tree of Life, including numerous bacteria and archaea that have not been isolated and their diversity is not fully understood6.
The expanded Tree of Life is particularly useful in assessing the diversity of an area, helping to determine whether specific habitats require protection. This information can be used in a variety of ways, such as identifying new drugs, combating diseases and improving the quality of crops. This information is also extremely valuable to conservation efforts. It can help biologists identify the areas most likely to contain cryptic species with important metabolic functions that may be at risk from anthropogenic change. While funds to protect biodiversity are important, the best method to preserve the biodiversity of the world is to equip the people of developing nations with the information they require to take action locally and encourage conservation.
Phylogeny
A phylogeny, also known as an evolutionary tree, illustrates the connections between various groups of organisms. click through the up coming website page can build a phylogenetic diagram that illustrates the evolution of taxonomic groups using molecular data and morphological similarities or differences. The concept of phylogeny is fundamental to understanding biodiversity, evolution and genetics.
A basic phylogenetic tree (see Figure PageIndex 10 Finds the connections between organisms that have similar characteristics and have evolved from an ancestor with common traits. These shared traits can be analogous or homologous. Homologous traits are the same in terms of their evolutionary journey. Analogous traits could appear like they are but they don't have the same origins. Scientists arrange similar traits into a grouping called a the clade. Every organism in a group have a common characteristic, like amniotic egg production. They all evolved from an ancestor who had these eggs. A phylogenetic tree is constructed by connecting clades to identify the organisms who are the closest to one another.
Scientists utilize molecular DNA or RNA data to build a phylogenetic chart that is more accurate and precise. This data is more precise than morphological data and provides evidence of the evolutionary history of an organism or group. Researchers can use Molecular Data to estimate the age of evolution of organisms and determine how many organisms share an ancestor common to all.
The phylogenetic relationships between species are influenced by many factors, including phenotypic plasticity a kind of behavior that changes in response to specific environmental conditions. This can cause a particular trait to appear more similar to one species than other species, which can obscure the phylogenetic signal. However, this problem can be solved through the use of techniques like cladistics, which combine analogous and homologous features into the tree.
In addition, phylogenetics helps determine the duration and speed at which speciation occurs. This information can aid conservation biologists to decide which species to protect from the threat of extinction. It is ultimately the preservation of phylogenetic diversity which will lead to an ecosystem that is complete and balanced.
Evolutionary Theory
The fundamental concept of evolution is that organisms acquire various characteristics over time as a result of their interactions with their environments. Many scientists have developed 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 individual requirements, the Swedish taxonomist Carolus Linnaeus (1707-1778) who conceived the modern taxonomy system that is hierarchical, as well as Jean-Baptiste Lamarck (1844-1829), who suggested that the use or absence of traits can lead to changes that are passed on to the next generation.
In the 1930s and 1940s, ideas from a variety of fields--including natural selection, genetics, and particulate inheritance -- came together to form the current synthesis of evolutionary theory which explains how evolution is triggered by the variation of genes within a population and how those variations change over time as a result of natural selection. This model, which incorporates genetic drift, mutations as well as gene flow and sexual selection is mathematically described mathematically.
Recent developments in the field of evolutionary developmental biology have revealed that variations can be introduced into a species by mutation, genetic drift, and reshuffling of genes during sexual reproduction, as well as through migration between populations. These processes, as well as others like directional selection and genetic erosion (changes in the frequency of an individual's genotype over time) can lead to evolution which is defined by changes in the genome of the species over time and also by changes in phenotype as time passes (the expression of the genotype in an individual).
Students can gain a better understanding of the concept of phylogeny through incorporating evolutionary thinking into all aspects of biology. In a recent study conducted by Grunspan and colleagues. It was found that teaching students about the evidence for evolution boosted their acceptance of evolution during an undergraduate biology course. For more details on how to teach about evolution read The Evolutionary Power of Biology in all Areas of Biology or Thinking Evolutionarily as a Framework for Integrating Evolution into Life Sciences Education.
Evolution in Action
Scientists have looked at evolution through the past, analyzing fossils and comparing species. They also study living organisms. Evolution is not a distant event, but an ongoing process that continues to be observed today. Bacteria transform and resist antibiotics, viruses re-invent themselves and elude new medications, and animals adapt their behavior to the changing environment. The results are often evident.
It wasn't until late 1980s that biologists understood that natural selection could be observed in action as well. The reason is that different traits have different rates of survival and reproduction (differential fitness), and can be transferred from one generation to the next.
In the past, if a certain allele - the genetic sequence that determines color - was found in a group of organisms that interbred, it could be more common than other allele. As time passes, this could mean that the number of moths with black pigmentation in a group may increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
Monitoring evolutionary changes in action is much easier when a species has a fast generation turnover like bacteria. Since 1988, Richard Lenski, a biologist, has been tracking twelve populations of E.coli that are descended from a single strain. Samples from each population were taken regularly, and more than 50,000 generations of E.coli have passed.
Lenski's research has shown that mutations can drastically alter the efficiency with which a population reproduces--and so the rate at which it alters. It also demonstrates that evolution takes time, something that is difficult for some to accept.
Another example of microevolution is that mosquito genes that confer resistance to pesticides show up more often in populations where insecticides are used. This is because the use of pesticides creates a selective pressure that favors individuals with resistant genotypes.
The rapidity of evolution has led to a greater awareness of its significance especially in a planet shaped largely by human activity. This includes pollution, climate change, and habitat loss that hinders many species from adapting. Understanding evolution can help us make smarter decisions regarding the future of our planet and the lives of its inhabitants.