20 Tips To Help You Be More Efficient At Evolution Site
The Academy's Evolution Site
Biological evolution is one of the most important concepts in biology. The Academies have been active for a long time in helping those interested in science understand the theory of evolution and how it permeates every area of scientific inquiry.
This site provides a range of sources for students, teachers and general readers of evolution. It also includes important 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 life. It is an emblem of love and unity across many cultures. It also has important practical uses, like providing a framework to understand the evolution of species and how they react to changing environmental conditions.
Early attempts to describe the biological world 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 fragments of DNA, have significantly increased the diversity of a Tree of Life2. However the trees are mostly made up of eukaryotes. Bacterial diversity is still largely unrepresented3,4.
By avoiding the need for direct experimentation and observation, genetic techniques have allowed us to represent the Tree of Life in a more precise manner. We can create trees using molecular techniques like the small-subunit ribosomal gene.
The Tree of Life has been dramatically expanded through genome sequencing. However there is still a lot of biodiversity to be discovered. This is particularly true of microorganisms that are difficult to cultivate and are often only represented in a single specimen5. A recent analysis of all genomes known to date has produced a rough draft of the Tree of Life, including numerous bacteria and archaea that have not been isolated and which are not well understood.
This expanded Tree of Life can be used to determine the diversity of a particular area and determine if specific habitats need special protection. This information can be used in a variety of ways, from identifying new treatments to fight disease to enhancing the quality of crops. It is also beneficial in conservation efforts. It can aid biologists in identifying the areas most likely to contain cryptic species that could have important metabolic functions that may be at risk of anthropogenic changes. While funds to protect biodiversity are crucial however, the most effective method to protect the world's biodiversity is for more people in developing countries to be empowered with the necessary knowledge to take action locally to encourage conservation from within.
Phylogeny
A phylogeny, also known as an evolutionary tree, illustrates the relationships between groups of organisms. Using molecular data, morphological similarities and differences, or ontogeny (the process of the development of an organism), scientists can build an phylogenetic tree that demonstrates the evolution of taxonomic categories. Phylogeny is essential in understanding the evolution of biodiversity, evolution and genetics.
A basic phylogenetic tree (see Figure PageIndex 10 ) identifies the relationships between organisms that share similar traits that evolved from common ancestors. These shared traits can be either homologous or analogous. Homologous traits are similar in their underlying evolutionary path and analogous traits appear similar, but do not share the same origins. Scientists organize similar traits into a grouping referred to as a clade. For example, all of the organisms in a clade share the characteristic of having amniotic eggs and evolved from a common ancestor which had these eggs. A phylogenetic tree can be constructed by connecting clades to determine the organisms which are the closest to each other.
To create a more thorough and accurate phylogenetic tree, scientists rely on molecular information from DNA or RNA to determine the connections between organisms. This information is more precise and gives evidence of the evolution history of an organism. The use of molecular data lets researchers determine the number of species that share an ancestor common to them and estimate their evolutionary age.
The phylogenetic relationships between species can be influenced by several factors, including phenotypic flexibility, a type of behavior that changes in response to unique environmental conditions. This can make a trait appear more similar to one species than to the other, obscuring the phylogenetic signals. This issue can be cured by using cladistics, which incorporates an amalgamation of homologous and analogous traits in the tree.
In addition, phylogenetics can aid in predicting the time and pace of speciation. This information can aid conservation biologists in making decisions about which species to protect from the threat of extinction. In the end, it is the preservation of phylogenetic diversity that will lead to 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. 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 believed that an organism would evolve gradually according to its needs, the Swedish botanist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical taxonomy Jean-Baptiste Lamarck (1744-1829) who suggested that use or disuse of traits cause changes that can be passed on to offspring.
In the 1930s and 1940s, ideas from different fields, including genetics, natural selection and particulate inheritance, were brought together to create a modern synthesis of evolution theory. This describes how evolution occurs by the variation in genes within a population and how these variants change over time as a result of natural selection. This model, which includes mutations, genetic drift in gene flow, and sexual selection can be mathematically described.
Recent discoveries in the field of evolutionary developmental biology have revealed how variation can be introduced to a species by genetic drift, mutations or reshuffling of genes in sexual reproduction and migration between populations. These processes, as well as others like directional selection and genetic erosion (changes in the frequency of the genotype over time), can lead to evolution that is defined as change in the genome of the species over time and the change in phenotype over time (the expression of that genotype in an individual).
Students can gain a better understanding of the concept of phylogeny by using evolutionary thinking into all aspects of biology. A recent study by Grunspan and colleagues, for example, showed that teaching about the evidence that supports evolution helped students accept the concept of evolution in a college biology course. To learn more about how to teach about evolution, look up The Evolutionary Potential of all Areas of Biology and Thinking Evolution arily A Framework for Infusing Evolution into Life Sciences Education.
Evolution in Action
Traditionally scientists have studied evolution through looking back, studying fossils, comparing species and studying living organisms. But evolution isn't a thing that occurred in the past. It's an ongoing process, taking place right now. Bacteria mutate and resist antibiotics, viruses reinvent themselves and escape new drugs and animals alter their behavior to the changing climate. The changes that result are often visible.
However, it wasn't until late 1980s that biologists understood that natural selection can be observed in action as well. The main reason is that different traits result in an individual rate of survival as well as reproduction, and may be passed down from one generation to another.
In the past when one particular allele - the genetic sequence that controls coloration - was present in a group of interbreeding organisms, it might rapidly become more common than other alleles. 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.
It is easier to observe evolutionary change when the species, like bacteria, has a high generation turnover. Since 1988, Richard Lenski, a biologist, has been tracking twelve populations of E.coli that descend from one strain. Samples of each population have been taken regularly, and more than 500.000 generations of E.coli have been observed to have passed.
Lenski's work has demonstrated that mutations can drastically alter the efficiency with which a population reproduces--and so, the rate at which it changes. It also shows that evolution takes time, which is hard for some to accept.
Microevolution can be observed in the fact that mosquito genes for pesticide resistance are more common in populations where insecticides are used. This is due to pesticides causing an exclusive pressure that favors individuals who have resistant genotypes.
The speed at which evolution takes place has led to a growing appreciation of its importance in a world that is shaped by human activity--including climate change, pollution, and the loss of habitats that hinder the species from adapting. Understanding evolution will aid you in making better decisions about the future of our planet and its inhabitants.