The Academy's Evolution Site
Biology is one of the most fundamental concepts in biology. The Academies have long been involved in helping those interested in science comprehend the theory of evolution and how it influences all areas of scientific exploration.
This site provides students, teachers and general readers with a variety of educational resources on evolution. It includes the most important video clips from NOVA and WGBH's science programs on DVD.
Tree of Life
The Tree of Life is an ancient symbol that symbolizes the interconnectedness of all life. It is an emblem of love and harmony in a variety of cultures. It also has many practical uses, like providing a framework to understand the history of species and how they react to changes in environmental conditions.
The first attempts at depicting the world of biology focused on categorizing species into distinct categories that were identified by their physical and metabolic characteristics1. These methods, based on the sampling of various parts of living organisms, or sequences of small fragments of their DNA significantly expanded the diversity that could be represented in the tree of life2. These trees are largely composed by eukaryotes, and bacteria are largely underrepresented3,4.
Genetic techniques have greatly broadened our ability to represent the Tree of Life by circumventing the requirement for direct observation and experimentation. In particular, molecular methods enable us to create trees by using sequenced markers such as the small subunit of ribosomal RNA gene.
The Tree of Life has been greatly expanded thanks to genome sequencing. However there is a lot of biodiversity to be discovered. This is especially relevant to microorganisms that are difficult to cultivate and are typically found in one sample5. A recent analysis of all genomes produced an initial draft of the Tree of Life. This includes a variety of archaea, bacteria and other organisms that have not yet been isolated, or the diversity of which is not fully understood6.
The expanded Tree of Life is particularly beneficial in assessing the biodiversity of an area, helping to determine if certain habitats require special protection. The information can be used in a variety of ways, from identifying the most effective medicines to combating disease to enhancing the quality of crop yields. This information is also beneficial in conservation efforts. It can aid biologists in identifying the areas that are most likely to contain cryptic species that could have important metabolic functions that may be vulnerable to anthropogenic change. Although funds to protect biodiversity are essential but the most effective way to ensure the preservation of biodiversity around the world is for more people in developing countries to be equipped with the knowledge to act locally to promote conservation from within.
Phylogeny
A phylogeny, also called an evolutionary tree, illustrates the relationships between various groups of organisms. Scientists can build a phylogenetic chart that shows the evolution of taxonomic groups based on molecular data and morphological differences or similarities. Phylogeny plays a crucial role in understanding the relationship between genetics, biodiversity and evolution.
A basic phylogenetic tree (see Figure PageIndex 10 ) determines the relationship between organisms with similar traits that have evolved from common ancestors. These shared traits could be homologous, or analogous. Homologous characteristics are identical in their evolutionary paths. Analogous traits could appear like they are but they don't share the same origins. Scientists group similar traits into a grouping called a the clade. Every organism in a group have a common characteristic, for example, amniotic egg production. 바카라 에볼루션 derived from an ancestor who had these eggs. A phylogenetic tree can be constructed by connecting clades to determine the organisms that are most closely related to each other.
To create a more thorough and accurate phylogenetic tree scientists make use of molecular data from DNA or RNA to determine the relationships between organisms. This information is more precise than the morphological data and provides evidence of the evolutionary history of an organism or group. Molecular data allows researchers to determine the number of organisms that share the same ancestor and estimate their evolutionary age.
The phylogenetic relationships of organisms can be affected by a variety of factors, including phenotypic flexibility, a kind of behavior that changes in response to unique environmental conditions. This can cause a trait to appear more like a species another, clouding the phylogenetic signal. However, this problem can be cured by the use of techniques such as cladistics that incorporate a combination of homologous and analogous features into the tree.
In addition, phylogenetics helps determine the duration and rate of speciation. This information can help conservation biologists decide the species they should safeguard from extinction. Ultimately, it is the preservation of phylogenetic diversity that will result in an ecologically balanced and complete ecosystem.
Evolutionary Theory
The central theme in evolution is that organisms change over time as a result of their interactions with their environment. Many theories of evolution have been developed by a wide variety of scientists, including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who believed that an organism would evolve gradually according to its requirements, 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 causes changes that can be passed on to the offspring.
In the 1930s and 1940s, theories from a variety of fields--including genetics, natural selection and particulate inheritance--came together to create the modern evolutionary theory which explains how evolution is triggered by the variation of genes within a population and how those variations change over time due to natural selection. This model, known as genetic drift mutation, gene flow, and sexual selection, is a cornerstone of current evolutionary biology, and can be mathematically described.
Recent discoveries in the field of evolutionary developmental biology have demonstrated that genetic variation can be introduced into a species via mutation, genetic drift and reshuffling of genes during sexual reproduction, and also through migration between populations. These processes, along with other ones like directional selection and genetic erosion (changes in the frequency of an individual's genotype over time), can lead to evolution that is defined as change in the genome of the species over time, and also the change in phenotype over time (the expression of that genotype in the individual).
Incorporating evolutionary thinking into all areas of biology education can improve students' understanding of phylogeny and evolution. A recent study by Grunspan and colleagues, for instance demonstrated that teaching about the evidence that supports evolution helped students accept the concept of evolution in a college biology class. For more information on how to teach about evolution, 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 studied evolution by looking in the past, studying fossils, and comparing species. They also study living organisms. But evolution isn't a thing that happened in the past. It's an ongoing process that is taking place in the present. Viruses reinvent themselves to avoid new drugs and bacteria evolve to resist antibiotics. Animals adapt their behavior in the wake of the changing environment. The changes that result are often evident.
It wasn't until the 1980s when biologists began to realize that natural selection was also in action. The main reason is that different traits can confer the ability to survive at different rates and reproduction, and they can be passed on from generation to generation.
In the past, if one particular allele - the genetic sequence that defines color in a group of interbreeding organisms, it could quickly become more prevalent than other alleles. In time, this could mean that the number of moths sporting black pigmentation may 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, Richard Lenski, a biologist, has studied twelve populations of E.coli that are descended from one strain. Samples from each population have been taken regularly, and more than 500.000 generations of E.coli have passed.
Lenski's work has demonstrated that a mutation can profoundly alter the efficiency with the rate at which a population reproduces, and consequently the rate at which it changes. It also demonstrates that evolution is slow-moving, a fact that some find hard to accept.
Another example of microevolution is that mosquito genes that are resistant to pesticides appear more frequently in populations where insecticides are used. This is due to the fact that the use of pesticides creates a pressure that favors those with resistant genotypes.
The rapid pace at which evolution takes place has led to an increasing awareness of its significance in a world that is shaped by human activities, including climate change, pollution and the loss of habitats which prevent many species from adapting. Understanding evolution will aid you in making better decisions about the future of the planet and its inhabitants.