The Academy's Evolution Site
Biological evolution is a central concept in biology. The Academies are involved in helping those who are interested in science to comprehend the evolution theory and how it is permeated in all areas of scientific research.
This site provides teachers, students and general readers with a range of learning resources on evolution. It has important video clips 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 life. It is an emblem of love and harmony in a variety of cultures. It also has important practical applications, like providing a framework for understanding the history of species and how they react to changes in environmental conditions.
The first attempts to depict the biological world were founded on categorizing organisms on their metabolic and physical characteristics. These methods, which relied on sampling of different parts of living organisms or on small fragments of their DNA, greatly increased the variety of organisms that could be included in the tree of life2. These trees are mostly populated by eukaryotes and bacteria are largely underrepresented3,4.
Genetic techniques have greatly expanded our ability to visualize 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.
The Tree of Life has been dramatically expanded through genome sequencing. However there is a lot of biodiversity to be discovered. This is particularly the case for microorganisms which are difficult to cultivate, and which are usually only present in a single sample5. A recent analysis of all known genomes has produced a rough draft version of the Tree of Life, including numerous bacteria and archaea that have not been isolated, and whose diversity is poorly understood6.
This expanded Tree of Life can be used to determine the diversity of a particular area and determine if certain habitats require special protection. This information can be utilized in a range of ways, from identifying new medicines to combating disease to enhancing the quality of crop yields. This information is also extremely useful in conservation efforts. It can aid biologists in identifying the areas most likely to contain cryptic species that could have important metabolic functions that could be at risk from anthropogenic change. Although funding to protect biodiversity are crucial, ultimately the best way to preserve the world's biodiversity is for more people in developing countries to be empowered with the knowledge to take action locally to encourage conservation from within.
Phylogeny
A phylogeny, also called an evolutionary tree, illustrates the connections between groups of organisms. Scientists can construct a phylogenetic chart that shows the evolution of taxonomic groups using molecular data and morphological similarities or differences. Phylogeny is essential in understanding biodiversity, evolution and genetics.
A basic phylogenetic Tree (see Figure PageIndex 10 Finds the connections between organisms with similar traits and evolved from a common ancestor. These shared traits could be either analogous or homologous. Homologous traits are identical in their evolutionary roots and analogous traits appear similar, but do not share the same ancestors. Scientists group similar traits into a grouping referred to as a clade. All organisms in a group share a characteristic, like amniotic egg production. They all derived from an ancestor that had these eggs. A phylogenetic tree is constructed by connecting clades to determine the organisms who are the closest to one another.
To create a more thorough and accurate phylogenetic tree, scientists make use of molecular data from DNA or RNA to establish the relationships between organisms. This data is more precise than the morphological data and gives evidence of the evolutionary history of an individual or group. Researchers can utilize Molecular Data to estimate the evolutionary age of living organisms and discover how many organisms have an ancestor common to all.
The phylogenetic relationships of organisms are influenced by many factors, including phenotypic plasticity a kind of behavior that alters in response to specific environmental conditions. This can make a trait appear more similar to a species than another and obscure the phylogenetic signals. However, this problem can be reduced by the use of methods like cladistics, which include a mix of similar and homologous traits into the tree.
Additionally, phylogenetics can aid in predicting the time and pace of speciation. This information will assist conservation biologists in deciding 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 complete and balanced.
Evolutionary Theory
The fundamental concept of evolution is that organisms develop different features over time due to their interactions with their surroundings. Many theories of evolution have been proposed by a wide variety of scientists such as the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who proposed that a living organism develop gradually according to its needs, the Swedish botanist Carolus Linnaeus (1707-1778) who developed modern hierarchical taxonomy, and Jean-Baptiste Lamarck (1744-1829) who suggested that the use or non-use of traits causes changes that can be passed on to the offspring.
In the 1930s and 1940s, concepts from various fields, including genetics, natural selection, and particulate inheritance--came together to form the modern evolutionary theory synthesis that explains how evolution happens through the variations 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, gene flow and sexual selection can be mathematically described mathematically.
Recent advances in the field of evolutionary developmental biology have revealed how variations can be introduced to a species via genetic drift, mutations or reshuffling of genes in sexual reproduction and migration between populations. These processes, along with others such as directionally-selected selection and erosion of genes (changes in the frequency of genotypes over time), can lead towards evolution. Evolution is defined by changes in the genome over time and changes in phenotype (the expression of genotypes in individuals).
Students can better understand phylogeny by incorporating evolutionary thinking throughout all aspects of biology. A recent study by Grunspan and colleagues, for instance revealed that teaching students about the evidence supporting evolution helped students accept the concept of evolution in a college biology class. For more details on how to teach evolution look up The Evolutionary Potential in all Areas of Biology or Thinking Evolutionarily as a Framework for Integrating Evolution into Life Sciences Education.
Evolution in Action
Scientists have traditionally studied evolution by looking in the past--analyzing fossils and comparing species. They also study living organisms. Evolution isn't a flims event, but a process that continues today. Bacteria mutate and resist antibiotics, viruses evolve and escape new drugs, and animals adapt their behavior to the changing environment. The changes that result are often easy to see.
It wasn't until the 1980s when biologists began to realize that natural selection was also at work. The key 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 one particular allele, the genetic sequence that defines color in a group of interbreeding species, it could rapidly become more common than the other alleles. As time passes, that could mean that the number of black moths within the population 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 evolutionary change when an organism, like bacteria, has a high generation turnover. Since 1988, biologist Richard Lenski has been tracking twelve populations of E. coli that descended from a single strain. samples from each population are taken every day and more than 50,000 generations have now passed.
Lenski's work has shown that mutations can alter the rate at which change occurs and the efficiency at which a population reproduces. It also shows that evolution takes time--a fact that some find hard to accept.
에볼루션 코리아 can be observed in the fact that mosquito genes that confer resistance to pesticides are more common in populations where insecticides are used. This is due to the fact that the use of pesticides causes a selective pressure that favors individuals who have resistant genotypes.
The speed at which evolution can take place has led to a growing recognition of its importance in a world shaped by human activity--including climate change, pollution, and the loss of habitats that prevent the species from adapting. Understanding the evolution process can assist you in making better choices about the future of our planet and its inhabitants.