The Academy's Evolution Site
The concept of biological evolution is a fundamental concept in biology. The Academies are involved in helping those who are interested in science understand evolution theory and how it can be applied throughout all fields of scientific research.
This site offers a variety of tools for teachers, students as well as general readers about 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 appears in many spiritual traditions and cultures as an emblem of unity and love. It also has important practical applications, like providing a framework for understanding the evolution of species and how they respond to changing environmental conditions.
Early attempts to describe the world of biology were founded on categorizing organisms on their metabolic and physical characteristics. These methods depend on the sampling of different parts of organisms or short DNA fragments, have greatly increased the diversity of a tree of Life2. These trees are mostly populated by eukaryotes and bacteria are largely underrepresented3,4.
Genetic techniques have greatly broadened our ability to depict the Tree of Life by circumventing the requirement for direct observation and experimentation. We can create trees using molecular techniques such as the small subunit ribosomal gene.
Despite the rapid growth of the Tree of Life through genome sequencing, a large amount of biodiversity remains to be discovered. This is especially true of microorganisms, which can be difficult to cultivate and are often only found in a single specimen5. A recent study of all genomes that are known has produced a rough draft of the Tree of Life, including a large number of bacteria and archaea that have not been isolated and which are not well understood.
The expanded Tree of Life can be used to evaluate the biodiversity of a specific region 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 crop yields. This information is also useful for conservation efforts. It can help biologists identify areas that are most likely to have cryptic species, which could have important metabolic functions, and could be susceptible to human-induced change. While funds to protect biodiversity are important, the best method to preserve the world's biodiversity is to empower the people of developing nations with the necessary knowledge to take action locally and encourage conservation.
Phylogeny
A phylogeny, also known as an evolutionary tree, illustrates the relationships between various groups of organisms. Using molecular data similarities and differences in morphology, or ontogeny (the course of development of an organism), scientists can build a phylogenetic tree that illustrates the evolutionary relationship between taxonomic groups. Phylogeny plays a crucial role in understanding biodiversity, genetics and evolution.
A basic phylogenetic tree (see Figure PageIndex 10 Finds the connections between organisms that have similar characteristics and have evolved from an ancestor that shared traits. These shared traits may be analogous or homologous. Homologous traits share their evolutionary origins and analogous traits appear similar, but do not share the same ancestors. Scientists arrange similar traits into a grouping known as a the clade. All members of a clade have a common trait, such as amniotic egg production. They all came from an ancestor with these eggs. A phylogenetic tree can be constructed by connecting clades to identify the organisms which are the closest to each other.
Scientists make use of DNA or RNA molecular data to create a phylogenetic chart which is more precise and detailed. This information is more precise and gives evidence of the evolution history of an organism. Researchers can utilize Molecular Data to determine the age of evolution of organisms and determine the number of organisms that share the same ancestor.
The phylogenetic relationships of organisms can be affected by a variety of factors, including phenotypic plasticity a type of behavior that alters in response to specific environmental conditions. This can cause a trait to appear more similar to one species than to another, obscuring the phylogenetic signals. However, this issue can be cured by the use of techniques like cladistics, which include a mix of similar and homologous traits into the tree.
In addition, phylogenetics can help predict the duration and rate of speciation. This information will assist conservation biologists in making decisions about which species to safeguard 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 central theme of evolution is that organisms develop distinct characteristics over time due to their interactions with their environment. Many scientists have developed theories of evolution, including the Islamic naturalist Nasir al-Din al-Tusi (1201-274), who believed that an organism could evolve according to its own requirements, the Swedish taxonomist Carolus Linnaeus (1707-1778), who created the modern hierarchical taxonomy, as well as Jean-Baptiste Lamarck (1844-1829), who believed that the use or absence of traits can lead to changes that are passed on to the next generation.
In look at here & 1940s, concepts from various areas, including genetics, natural selection and particulate inheritance, came together to form a contemporary synthesis of evolution theory. This defines how evolution occurs by the variation of genes in the population and how these variants change over time as a result of natural selection. This model, which is known as genetic drift mutation, gene flow, and sexual selection, is the foundation of current evolutionary biology, and is mathematically described.
Recent advances in evolutionary developmental biology have revealed how variation can be introduced to a species through genetic drift, mutations, reshuffling genes during sexual reproduction and the movement between populations. These processes, as well as others such as directional selection or genetic erosion (changes in the frequency of an individual's genotype over time) can lead to evolution which is defined by change in the genome of the species over time and the change in phenotype over time (the expression of that genotype in an individual).
Incorporating evolutionary thinking into all areas of biology education can improve students' understanding of phylogeny as well as evolution. A recent study conducted by Grunspan and colleagues, for example revealed that teaching students about the evidence supporting evolution increased students' understanding of evolution in a college biology class. For more information about how to teach evolution read The Evolutionary Potency in All Areas of Biology or Thinking Evolutionarily as a Framework for Integrating Evolution into Life Sciences Education.
Evolution in Action
Traditionally scientists have studied evolution through looking back--analyzing fossils, comparing species, and studying living organisms. Evolution isn't a flims event; it is a process that continues today. The virus reinvents itself to avoid new medications and bacteria mutate to resist antibiotics. Animals alter their behavior because of a changing environment. The resulting changes are often easy to see.
It wasn't until the 1980s when biologists began to realize that natural selection was at work. 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 one particular allele, the genetic sequence that defines color in a group of interbreeding organisms, it might rapidly become more common than all other alleles. As time passes, that could mean that 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.
It is easier to track evolution when a species, such as bacteria, has a high generation turnover. Since 1988, Richard Lenski, a biologist, has tracked twelve populations of E.coli that are descended from a single strain. Samples from each population were taken regularly, and more than 500.000 generations of E.coli have been observed to have passed.
Lenski's work has demonstrated that a mutation can profoundly alter the efficiency with which a population reproduces and, consequently, the rate at which it evolves. It also shows that evolution takes time, a fact that is difficult for some to accept.
Another example of microevolution is how mosquito genes that confer resistance to pesticides show up more often in areas where insecticides are employed. This is because the use of pesticides causes a selective pressure that favors individuals with resistant genotypes.
The rapidity of evolution has led to a growing recognition of its importance, especially in a world that is largely shaped by human activity. This includes the effects of climate change, pollution and habitat loss that prevents many species from adapting. Understanding evolution can assist you in making better choices about the future of the planet and its inhabitants.