The Academy's Evolution Site
The concept of biological evolution is among the most fundamental concepts in biology. The Academies are involved in helping those interested in science learn about the theory of evolution and how it is permeated throughout all fields of scientific research.
This site provides a range of sources for students, teachers, and general readers on evolution. It has important video clips from NOVA and WGBH's science programs on DVD.
Tree of Life
The Tree of Life, an ancient symbol, represents 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 history of species and how they react to changes in the environment.
Early attempts to describe the world of biology were based on categorizing organisms based on their physical and metabolic characteristics. These methods rely on the collection of various parts of organisms or fragments of DNA have significantly increased the diversity of a Tree of Life2. These trees are largely composed of eukaryotes, while bacteria are largely underrepresented3,4.
By avoiding the need for direct observation and experimentation, genetic techniques have enabled us to depict the Tree of Life in a more precise manner. We can construct trees using molecular methods like the small-subunit ribosomal gene.
Despite the dramatic expansion of the Tree of Life through genome sequencing, much biodiversity still is waiting to be discovered. This is particularly true for microorganisms that are difficult to cultivate and are usually found in a single specimen5. Recent analysis of all genomes produced an unfinished draft of a Tree of Life. This includes a variety of bacteria, archaea and other organisms that have not yet been isolated, or whose diversity has not been fully understood6.
This expanded Tree of Life is particularly useful in assessing the diversity of an area, which can help to determine if certain habitats require protection. This information can be used in a range of ways, from identifying new treatments to fight disease to enhancing crops. This information is also extremely valuable for conservation efforts. It helps biologists discover areas most likely to have species that are cryptic, which could have vital metabolic functions and be vulnerable to human-induced change. While conservation funds are essential, the best way to conserve the world's biodiversity is to equip more people in developing nations with the knowledge they need to take action locally and encourage conservation.
Phylogeny
A phylogeny, also called an evolutionary tree, illustrates the relationships between different groups of organisms. Scientists can build a phylogenetic chart that shows the evolution of taxonomic categories using molecular information and morphological similarities or differences. The phylogeny of a tree plays an important role in understanding genetics, biodiversity and evolution.
A basic phylogenetic Tree (see Figure PageIndex 10 Determines the relationship between organisms that have similar characteristics and have evolved from a common ancestor. These shared traits could be analogous or homologous. Homologous traits are the same in their evolutionary path. Analogous traits may look similar however they do not share the same origins. Scientists combine similar traits into a grouping called a Clade. For instance, all of the organisms that make up a clade share the characteristic of having amniotic eggs. They evolved from a common ancestor that had eggs. The clades are then linked to form a phylogenetic branch that can identify organisms that have the closest connection to each other.
For a more detailed and accurate phylogenetic tree scientists rely on molecular information from DNA or RNA to determine the connections between organisms. This information is more precise than morphological data and provides evidence of the evolutionary background of an organism or group. Molecular data allows researchers to identify the number of species that have the same ancestor and estimate their evolutionary age.
The phylogenetic relationship can be affected by a number of factors such as phenotypicplasticity. This is a type behavior that changes in response to particular environmental conditions. This can cause a characteristic to appear more similar in one species than another, obscuring the phylogenetic signal. This problem can be mitigated by using cladistics. This is a method that incorporates the combination of analogous and homologous features in the tree.
Additionally, phylogenetics aids predict the duration and rate at which speciation occurs. This information can assist conservation biologists in making choices about which species to safeguard from the threat of extinction. In the end, it is the conservation of phylogenetic diversity that will lead to an ecosystem that is complete and balanced.
Evolutionary Theory
The central theme in evolution is that organisms change over time as a result of their interactions with their environment. A variety of theories about evolution have been proposed by a wide variety of scientists including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who proposed that a living organism develop gradually according to its requirements as well as the Swedish botanist Carolus Linnaeus (1707-1778) who developed the modern hierarchical taxonomy, as well as Jean-Baptiste Lamarck (1744-1829) who suggested that the use or misuse of traits cause changes that could be passed on to offspring.
In the 1930s and 1940s, ideas from different fields, such as genetics, natural selection and particulate inheritance, merged to form a modern theorizing of evolution. This describes how evolution happens through the variation in genes within a population and how these variants change over time as a result of natural selection. This model, called genetic drift or mutation, gene flow, and sexual selection, is a cornerstone of modern evolutionary biology and can be mathematically described.
Recent developments in the field of evolutionary developmental biology have revealed that genetic variation can be introduced into a species via genetic drift, mutation, and reshuffling of genes in sexual reproduction, and also by migration between populations. These processes, along with others like directional selection and genetic erosion (changes in the frequency of the genotype over time) can lead to 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 within the individual).
Incorporating evolutionary thinking into all aspects of biology education can increase students' understanding of phylogeny as well as evolution. 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, look up 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 studied evolution by looking in the past, analyzing fossils and comparing species. They also observe living organisms. Evolution is not a distant moment; it is an ongoing process. Recommended Website evolve to stay away from new medications and bacteria mutate to resist antibiotics. Animals alter their behavior in the wake of a changing environment. The results are usually visible.
But it wasn't until the late-1980s that biologists realized that natural selection can be observed in action as well. The key is that different traits have different rates of survival and reproduction (differential fitness), and can be passed from one generation to the next.
In the past, if an allele - the genetic sequence that determines colour was found in a group of organisms that interbred, it could be more common than other allele. Over time, this would mean that the number of moths sporting black pigmentation in a group could 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 tracked twelve populations of E.coli that are descended from one strain. Samples from each population have been collected regularly and more than 50,000 generations of E.coli have passed.
Lenski's work has demonstrated that a mutation can profoundly alter the speed at which a population reproduces--and so the rate at which it evolves. It also demonstrates that evolution takes time, which is hard for some to accept.
Microevolution can also be seen in the fact that mosquito genes for resistance to pesticides are more prevalent in areas where insecticides have been used. This is due to pesticides causing an exclusive pressure that favors those with resistant genotypes.
The speed at which evolution can take place has led to an increasing recognition of its importance in a world that is shaped by human activities, including climate change, pollution, and the loss of habitats that prevent the species from adapting. Understanding the evolution process will assist you in making better choices regarding the future of the planet and its inhabitants.