The Academy's Evolution Site
Biological evolution is one of the most fundamental 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 all areas of scientific exploration.
This site provides teachers, students and general readers with a variety of educational resources on evolution. It includes key video clip from NOVA and WGBH produced science programs on DVD.
Tree of Life
The Tree of Life, an ancient symbol, symbolizes the interconnectedness of all life. It is used in many religions and cultures as an emblem of unity and love. It also has many practical applications, like providing a framework to understand the history of species and how they react to changes in environmental conditions.
Early approaches to depicting the world of biology focused on the classification of organisms into distinct categories which were identified by their physical and metabolic characteristics1. These methods, which depend on the sampling of different parts of organisms, or fragments of DNA have greatly increased the diversity of a tree of Life2. These trees are mostly populated by eukaryotes and bacteria are largely underrepresented3,4.
In avoiding the necessity of direct observation and experimentation, genetic techniques have enabled us to depict the Tree of Life in a much more accurate way. We can create trees by using molecular methods such as the small subunit ribosomal gene.
The Tree of Life has been dramatically expanded through genome sequencing. However, there is still much diversity to be discovered. This is especially the case for microorganisms which are difficult to cultivate, and are typically found in a single specimen5. A recent analysis of all genomes has produced a rough draft of the Tree of Life. This includes a variety of archaea, bacteria and other organisms that have not 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, assisting to determine if specific habitats require protection. This information can be used in a variety of ways, such as finding new drugs, fighting diseases and improving crops. The information is also incredibly valuable in conservation efforts. It helps biologists discover areas that are likely to be home to species that are cryptic, which could have vital metabolic functions and are susceptible to human-induced change. While funds 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 called an evolutionary tree) depicts the relationships between organisms. By using molecular information similarities and differences in morphology, or ontogeny (the course of development of an organism), scientists can build a phylogenetic tree which illustrates the evolutionary relationship between taxonomic categories. The concept of phylogeny is fundamental to understanding evolution, biodiversity and genetics.
A basic phylogenetic tree (see Figure PageIndex 10 ) identifies the relationships between organisms that share similar traits that evolved from common ancestral. These shared traits may be homologous, or analogous. Homologous traits are identical in their evolutionary origins and analogous traits appear like they do, but don't have the identical origins. Scientists organize similar traits into a grouping known as a the clade. All members of a clade have a common characteristic, like amniotic egg production. They all evolved from an ancestor with these eggs. The clades then join to form a phylogenetic branch to determine which organisms have the closest connection to each other.
Scientists make use of molecular DNA or RNA data to build a phylogenetic chart that is more accurate and detailed. This information is more precise and provides evidence of the evolution history of an organism. Molecular data allows researchers to determine the number of organisms that share a common ancestor and to estimate their evolutionary age.
Phylogenetic relationships can be affected by a number of factors that include the phenomenon of phenotypicplasticity. This is a type behavior that changes due to unique environmental conditions. This can cause a characteristic to appear more resembling to one species than to the other which can obscure the phylogenetic signal. This problem can be mitigated by using cladistics, which is a an amalgamation of analogous and homologous features in the tree.
Furthermore, phylogenetics may help predict the time and pace of speciation. 에볼루션 코리아 can aid conservation biologists in making decisions about which species to save from disappearance. Ultimately, it is the preservation of phylogenetic diversity that will create a complete and balanced ecosystem.
Evolutionary Theory
The main idea behind evolution is that organisms change over time as a result of their interactions with their environment. Many theories of evolution have been proposed by a variety of scientists including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who envisioned an organism developing slowly according to its requirements and needs, the Swedish botanist Carolus Linnaeus (1707-1778) who designed the modern hierarchical taxonomy, as well as Jean-Baptiste Lamarck (1744-1829) who suggested that the use or non-use of traits cause changes that could be passed on to the offspring.
In the 1930s & 1940s, concepts from various fields, including natural selection, genetics & particulate inheritance, merged to form a contemporary evolutionary theory. This describes how evolution is triggered by the variations in genes within a population and how these variants change with time due to natural selection. This model, which incorporates genetic drift, mutations, gene flow and sexual selection can be mathematically described mathematically.
Recent developments in evolutionary developmental biology have revealed how variation can be introduced to a species through 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 an individual's 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 over time (the expression of the genotype in the individual).
Incorporating evolutionary thinking into all areas of biology education could increase students' understanding of phylogeny and evolutionary. A recent study by Grunspan and colleagues, for instance demonstrated that teaching about the evidence supporting evolution helped students accept the concept of evolution in a college biology course. To learn more about how to teach about evolution, read The Evolutionary Potential in 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. But evolution isn't a thing that occurred in the past. It's an ongoing process, happening right now. Bacteria transform and resist antibiotics, viruses reinvent themselves and are able to evade new medications and animals alter their behavior in response to the changing environment. The results are usually evident.
But it wasn't until the late 1980s that biologists understood that natural selection can be observed in action as well. The main reason is that different traits can confer the ability to survive at different rates and reproduction, and can be passed down from one generation to the next.
In the past, if a certain allele - the genetic sequence that determines color - was present in a population of organisms that interbred, it could become more common than any other allele. As time passes, that could mean that the number of black moths within 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 evolutionary change when an organism, like bacteria, has a rapid generation turnover. Since 1988, biologist Richard Lenski has been tracking twelve populations of E. bacteria that descend from a single strain. samples of each population are taken every day, and over 50,000 generations have now passed.
Lenski's work has demonstrated that a mutation can dramatically alter the speed at which a population reproduces--and so the rate at which it evolves. It also proves that evolution is slow-moving, a fact that many find difficult to accept.
Another example of microevolution is the way mosquito genes for resistance to pesticides are more prevalent in areas where insecticides are used. This is due to the fact that the use of pesticides creates a selective pressure that favors those with resistant genotypes.
The rapidity of evolution has led to an increasing appreciation of its importance particularly in a world that is largely shaped by human activity. This includes the effects of climate change, pollution and habitat loss, which prevents many species from adapting. Understanding the evolution process can help us make better decisions about the future of our planet and the lives of its inhabitants.