The Academy's Evolution Site
Biology is a key concept in biology. The Academies are committed to helping those who are interested in science learn about the theory of evolution and how it can be applied throughout all fields of scientific research.
This site provides students, teachers and general readers with a variety of learning resources about evolution. It also includes important video clips 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 spiritual traditions and cultures as a symbol of unity and love. It can be used in many practical ways as well, such as providing a framework to understand the history of species and how they respond to changes in environmental conditions.
Early attempts to describe the world of biology were built on categorizing organisms based on their physical and metabolic characteristics. These methods, which are based on the sampling of different parts of organisms or short DNA fragments have greatly increased the diversity of a tree of Life2. However the trees are mostly composed of eukaryotes; bacterial diversity is not represented in a large way3,4.
By avoiding the need for direct experimentation and observation genetic techniques have enabled us to depict the Tree of Life in a more precise manner. Particularly, molecular methods enable us to create trees by using sequenced markers, such as the small subunit ribosomal RNA gene.
The Tree of Life has been dramatically expanded through genome sequencing. However there is a lot of diversity to be discovered. This is particularly true of microorganisms that are difficult to cultivate and are usually only represented in a single specimen5. A recent study of all genomes known to date has produced a rough draft version of the Tree of Life, including numerous bacteria and archaea that have not been isolated, and their diversity is not fully understood6.
The expanded Tree of Life can be used to evaluate the biodiversity of a specific area and determine if specific habitats need special protection. This information can be used in a variety of ways, including finding new drugs, fighting diseases and improving the quality of crops. The information is also incredibly beneficial for conservation efforts. It helps biologists discover areas most likely to be home to species that are cryptic, which could perform important metabolic functions and are susceptible to the effects of human activity. While conservation funds are essential, the best method to preserve the world's biodiversity is to equip more people in developing nations with the necessary knowledge to take action locally and encourage conservation.
Phylogeny
A phylogeny, also called an evolutionary tree, shows the relationships between various groups of organisms. Scientists can build a phylogenetic diagram that illustrates the evolution of taxonomic groups using molecular data 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 Identifies the relationships between organisms that have similar characteristics and have evolved from an ancestor with common traits. These shared traits are either homologous or analogous. Homologous traits are the same in their evolutionary paths. Analogous traits may look similar, but they do not share the same origins. Scientists organize similar traits into a grouping known as a clade. All organisms in a group have a common characteristic, for example, amniotic egg production. They all evolved from an ancestor who had these eggs. A phylogenetic tree is built by connecting the clades to identify the organisms who are the closest to one another.
For a more detailed and accurate phylogenetic tree, scientists make use of molecular data from DNA or RNA to identify the relationships among organisms. This information is more precise than morphological information and provides evidence of the evolution history of an organism or group. The use of molecular data lets researchers determine the number of species who share an ancestor common to them and estimate their evolutionary age.
The phylogenetic relationship can be affected by a variety of factors that include phenotypicplasticity. This is a kind of behaviour that can change in response to specific environmental conditions. This can cause a particular trait to appear more similar to one species than other species, which can obscure the phylogenetic signal. However, this issue can be solved through the use of techniques such as cladistics which incorporate a combination of homologous and analogous features into the tree.
Additionally, phylogenetics can help predict the duration and rate at which speciation occurs. This information can assist conservation biologists in making choices about which species to safeguard from disappearance. In the end, it's the conservation of phylogenetic diversity that will result in an ecosystem that is complete and balanced.
Evolutionary Theory
The fundamental concept of evolution is that organisms acquire distinct characteristics over time due to their interactions with their environment. Several theories of evolutionary change 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 slowly in accordance with its needs as well as the Swedish botanist Carolus Linnaeus (1707-1778) who designed the modern hierarchical taxonomy Jean-Baptiste Lamarck (1744-1829) who suggested that the use or non-use of traits cause changes that can be passed on to the offspring.
In the 1930s and 1940s, theories from various fields, such as natural selection, genetics & particulate inheritance, came together to create a modern theorizing of evolution. This defines how evolution happens through the variation in genes within a population and how these variations change with time due to natural selection. This model, known as genetic drift, mutation, gene flow and sexual selection, is a key element of current evolutionary biology, and is mathematically described.
Recent advances in evolutionary developmental biology have demonstrated 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, in conjunction with others, such as the directional selection process and the erosion of genes (changes in the frequency of genotypes over time) can result in evolution. Evolution is defined as changes in the genome over time as well as changes in phenotype (the expression of genotypes in an individual).
Incorporating evolutionary thinking into all aspects of biology education can improve students' understanding of phylogeny and evolutionary. A recent study conducted by Grunspan and colleagues, for example, showed that teaching about the evidence supporting evolution increased students' understanding of evolution in a college-level biology course. To learn more about how to teach about evolution, please read The Evolutionary Potential in all Areas of Biology and Thinking Evolutionarily: A Framework for Infusing Evolution in Life Sciences Education.
Evolution in Action
Scientists have traditionally looked at evolution through the past, studying fossils, and comparing species. They also study living organisms. Evolution is not a past moment; it is a process that continues today. Viruses reinvent themselves to avoid new drugs and bacteria evolve to resist antibiotics. Animals alter their behavior as a result of a changing world. The changes that result are often easy to see.
It wasn't until late 1980s that biologists realized that natural selection could be observed in action as well. The reason is that different traits confer 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 defines color in a group of interbreeding organisms, it might rapidly become more common than all other alleles. Over time, this would mean that the number of moths with black pigmentation in a population may increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
Observing evolutionary change in action is easier when a particular species has a rapid turnover of its generation, as with bacteria. Since 1988 the biologist Richard Lenski has been tracking twelve populations of E. Coli that descended from a single strain; samples from each population are taken regularly and over 50,000 generations have now been observed.
Lenski's work has shown that mutations can alter the rate at which change occurs and the efficiency of a population's reproduction. It also demonstrates that evolution takes time, which is difficult for some to accept.
Another example of microevolution is the way mosquito genes that are resistant to pesticides are more prevalent in areas where insecticides are used. 에볼루션 무료체험 is due to the fact that the use of pesticides creates a pressure that favors individuals who have resistant genotypes.
The rapidity of evolution has led to a growing appreciation of its importance especially in a planet that is largely shaped by human activity. This includes the effects of climate change, pollution and habitat loss that hinders many species from adapting. Understanding the evolution process will assist you in making better choices about the future of the planet and its inhabitants.