The Academy's Evolution Site
Biological evolution is a central concept in biology. The Academies are committed to helping those who are interested in science learn about the theory of evolution and how it is permeated in all areas of scientific research.
This site provides teachers, students and general readers with a variety of learning resources on evolution. It includes key video clip from NOVA and WGBH produced science programs on DVD.
Tree of Life
The Tree of Life is an ancient symbol that represents the interconnectedness of all life. It is a symbol of love and unity in many cultures. It also has many practical uses, like providing a framework for understanding the evolution of species and how they react to changes in the environment.
Early approaches to depicting the world of biology focused on categorizing organisms into distinct categories that were distinguished by physical and metabolic characteristics1. These methods, which rely on the collection of various parts of organisms, or DNA fragments, have greatly increased the diversity of a Tree of Life2. These trees are largely composed by eukaryotes, and bacteria are largely underrepresented3,4.
Genetic techniques have significantly expanded our ability to visualize the Tree of Life by circumventing the requirement for direct observation and experimentation. We can construct trees using molecular methods like the small-subunit ribosomal gene.
The Tree of Life has been dramatically expanded through genome sequencing. However, there is still much biodiversity to be discovered. This is particularly true for microorganisms, which are difficult to cultivate and are usually only represented in a single specimen5. Recent analysis of all genomes resulted in an initial draft of the Tree of Life. This includes a wide range of archaea, bacteria and other organisms that haven't yet been isolated, or their diversity is not thoroughly understood6.
The 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 utilized in a variety of ways, such as finding new drugs, battling diseases and enhancing crops. This information is also extremely beneficial in conservation efforts. It can help biologists identify areas that are likely to be home to species that are cryptic, which could have important metabolic functions and are susceptible to changes caused by humans. While funding to protect biodiversity are important, the most effective way to conserve the biodiversity of the world is to equip more people in developing nations with the knowledge they need to take action locally and encourage conservation.
Phylogeny
A phylogeny (also known as an evolutionary tree) depicts the relationships between different organisms. Using molecular data as well as morphological similarities and distinctions, or ontogeny (the process of the development of an organism) scientists can create a phylogenetic tree which illustrates the evolutionary relationships between taxonomic groups. 에볼루션바카라 of phylogeny is crucial in understanding genetics, biodiversity and evolution.
A basic phylogenetic Tree (see Figure PageIndex 10 Identifies the relationships between organisms with similar characteristics and have evolved from an ancestor with common traits. These shared traits may be analogous or homologous. Homologous traits are similar in terms of their evolutionary path. Analogous traits may look like they are, but they do not share the same origins. Scientists organize similar traits into a grouping referred to as a clade. For instance, all the species in a clade have the characteristic of having amniotic eggs and evolved from a common ancestor that had eggs. A phylogenetic tree can be constructed by connecting the clades to determine the organisms who are the closest to each other.
For a more precise and accurate phylogenetic tree scientists use molecular data from DNA or RNA to determine 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 organisms that share an ancestor common to them and estimate their evolutionary age.
The phylogenetic relationships of organisms can be influenced by several factors, including phenotypic plasticity a kind of behavior that changes in response to unique environmental conditions. This can cause a characteristic to appear more similar to one species than another which can obscure the phylogenetic signal. This problem can be addressed by using cladistics. This is a method that incorporates an amalgamation of analogous and homologous features in the tree.
Additionally, phylogenetics aids predict the duration and rate of speciation. This information can aid conservation biologists to make decisions about which species they should protect from the threat of extinction. In the end, it's the preservation of phylogenetic diversity that will lead to an ecologically balanced and complete ecosystem.
Evolutionary Theory
The fundamental concept in evolution is that organisms change over time due to their interactions with their environment. Many scientists have proposed 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 needs, the Swedish taxonomist Carolus Linnaeus (1707-1778) who developed the modern taxonomy system that is hierarchical as well as Jean-Baptiste Lamarck (1844-1829), who believed that the usage or non-use of traits can cause changes that are passed on to the next generation.
In the 1930s & 1940s, theories from various areas, including genetics, natural selection, and particulate inheritance, came together to create a modern synthesis of evolution theory. This defines how evolution is triggered by the variation in genes within a population and how these variants change with time due to natural selection. This model, known as genetic drift, mutation, gene flow, and sexual selection, is the foundation of the current evolutionary biology and can be mathematically explained.
Recent discoveries in the field of evolutionary developmental biology have revealed that genetic variation can be introduced into a species via genetic drift, mutation, and reshuffling genes during sexual reproduction, as well as by migration between populations. These processes, along with others such as directional selection or genetic erosion (changes in the frequency of a 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 the genotype in the individual).
Students can better understand the concept of phylogeny by using 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 during the course of a college biology. For more information on how to teach about evolution, read The Evolutionary Potential of All Areas of Biology and Thinking Evolutionarily A Framework for Infusing the Concept of Evolution into Life Sciences Education.
Evolution in Action
Traditionally scientists have studied evolution through looking back, studying fossils, comparing species and observing 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 antibiotics and bacteria transform to resist antibiotics. Animals adapt their behavior as a result of a changing world. The results are often apparent.
However, it wasn't until late 1980s that biologists realized that natural selection could be observed in action as well. The key is that various characteristics result in different rates of survival and reproduction (differential fitness), and can be transferred from one generation to the next.
In the past when one particular allele, the genetic sequence that controls coloration - was present in a group of interbreeding organisms, it might quickly become more prevalent than all other alleles. As time passes, that could mean the number of black moths in a particular population could rise. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
Monitoring evolutionary changes in action is easier when a species has a rapid generation turnover, as with bacteria. Since 1988, Richard Lenski, a biologist, has studied twelve populations of E.coli that descend from one strain. The samples of each population were taken regularly and more than 50,000 generations of E.coli have passed.
Lenski's research has demonstrated that mutations can alter the rate at which change occurs and the rate 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 the way mosquito genes for resistance to pesticides are more prevalent in areas where insecticides are employed. Pesticides create an enticement that favors individuals who have resistant genotypes.
The speed at which evolution can take place has led to an increasing appreciation of its importance in a world that is shaped by human activity, including climate changes, pollution and the loss of habitats that prevent many species from adapting. Understanding evolution will aid you in making better decisions about the future of our planet and its inhabitants.