The Academy's Evolution Site
The concept of biological evolution is among 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 permeates all areas of scientific exploration.
This site provides a wide range of resources for teachers, students and general readers of evolution. It includes the most important video clips from NOVA and the WGBH-produced science programs on DVD.
Tree of Life
The Tree of Life, an ancient symbol, represents the interconnectedness of all life. It is a symbol of love and unity across many cultures. 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 changing environmental conditions.
The first attempts at depicting the biological world focused on categorizing species into distinct categories that had been distinguished by their physical and metabolic characteristics1. These methods, which rely on the collection of various parts of organisms or fragments of DNA, have greatly increased the diversity of a Tree of Life2. The trees are mostly composed by eukaryotes and bacterial diversity is vastly underrepresented3,4.
By avoiding the necessity for direct observation and experimentation genetic techniques have enabled us to depict the Tree of Life in a more precise way. Particularly, molecular methods allow us to construct trees by using sequenced markers such as the small subunit ribosomal RNA gene.
Despite the rapid expansion of the Tree of Life through genome sequencing, a large amount of biodiversity is waiting to be discovered. This is especially the case for microorganisms which are difficult to cultivate, and are usually found in one sample5. A recent analysis of all genomes that are known has produced a rough draft of the Tree of Life, including numerous archaea and bacteria that have not been isolated and their diversity is not fully understood6.
The expanded Tree of Life can be used to determine the diversity of a specific area and determine if particular habitats require special protection. This information can be used in a variety of ways, such as identifying new drugs, combating diseases and improving the quality of crops. This information is also extremely valuable for conservation efforts. It can aid biologists in identifying areas most likely to be home to species that are cryptic, which could perform important metabolic functions and are susceptible to changes caused by humans. Although funding to protect biodiversity are essential but the most effective way to preserve the world's biodiversity is for more people living in developing countries to be empowered with the necessary knowledge to take action locally to encourage conservation from within.
Phylogeny
A phylogeny, also called an evolutionary tree, shows the relationships between groups of organisms. Scientists can construct a phylogenetic chart that shows the evolutionary relationships between taxonomic categories using molecular information and morphological similarities or differences. The phylogeny of a tree plays an important role in understanding biodiversity, genetics and evolution.
A basic phylogenetic tree (see Figure PageIndex 10 ) is a method of identifying the relationships between organisms with similar traits that have evolved from common ancestors. These shared traits can be either homologous or analogous. Homologous characteristics are identical in terms of their evolutionary path. Analogous traits may look similar, but they do not share the same origins. Scientists arrange similar traits into a grouping referred to as a clade. For example, all of the species in a clade share the characteristic of having amniotic eggs. They evolved from a common ancestor who had these eggs. A phylogenetic tree is then built by connecting the clades to determine the organisms which are the closest to each other.
To create a more thorough and accurate phylogenetic tree, scientists make use of molecular data from DNA or RNA to establish the connections between organisms. This information is more precise than morphological data and gives evidence of the evolutionary background of an organism or group. Researchers can use Molecular Data to estimate the evolutionary age of organisms and determine how many species have an ancestor common to all.
The phylogenetic relationship can be affected by a variety of factors that include the phenotypic plasticity. This is a type behavior that changes in response to unique environmental conditions. This can cause a particular trait to appear more similar to one species than other species, which can obscure the phylogenetic signal. This problem can be addressed by using cladistics. This is a method that incorporates a combination of homologous and analogous features in the tree.
Additionally, phylogenetics aids predict the duration and rate of speciation. This information can help conservation biologists make decisions about the species they should safeguard from the threat of extinction. In the end, it's the preservation of phylogenetic diversity which will create an ecosystem that is complete and balanced.
Evolutionary Theory
The central theme of evolution is that organisms develop different features over time based on their interactions with their surroundings. Several theories of evolutionary change have been developed by a variety of scientists such as the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who believed that an organism would evolve slowly in accordance with its requirements as well as the Swedish botanist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical taxonomy Jean-Baptiste Lamarck (1744-1829) who suggested that the use or misuse of traits causes changes that can be passed onto offspring.
In the 1930s and 1940s, theories from various fields, including genetics, natural selection, and particulate inheritance, were brought together to form a modern evolutionary theory. This explains how evolution occurs by the variations in genes within the population and how these variations alter over time due to natural selection. This model, called genetic drift, mutation, gene flow and sexual selection, is the foundation of the 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 through mutation, genetic drift and reshuffling of genes in sexual reproduction, as well as by migration between populations. These processes, as well as others, such as the directional selection process and the erosion of genes (changes to the frequency of genotypes over time), can lead towards evolution. Evolution is defined as changes in the genome over time as well as changes in the phenotype (the expression of genotypes in an individual).
Incorporating evolutionary thinking into all areas of biology education can increase student understanding of the concepts of phylogeny and evolution. In a study by Grunspan et al. It was found that teaching students about the evidence for evolution boosted their understanding of evolution during an undergraduate biology course. For more details on how to teach about evolution read The Evolutionary Power of Biology in All Areas of Biology or Thinking Evolutionarily A Framework for Infusing Evolution into Life Sciences Education.
Evolution in Action
Scientists have looked at evolution through the past--analyzing fossils and comparing species. They also observe living organisms. However, evolution isn't something that occurred in the past; it's an ongoing process happening in the present. Viruses reinvent themselves to avoid new antibiotics and bacteria transform to resist antibiotics. Animals adapt their behavior as a result of a changing environment. The results are often apparent.
It wasn't until late 1980s that biologists began realize that natural selection was also at work. 에볼루션 사이트 is that different traits have different rates of survival and reproduction (differential fitness) and are transferred from one generation to the next.
In the past, if one particular allele - the genetic sequence that determines coloration--appeared in a population of interbreeding species, it could quickly become more common than all other alleles. Over time, that would mean the number of black moths in the population could increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
Monitoring evolutionary changes in action is easier when a particular species has a rapid generation turnover such as bacteria. Since 1988 the biologist Richard Lenski has been tracking twelve populations of E. Coli that descended from a single strain. samples of each population are taken every day, and over 500.000 generations have been observed.
Lenski's research has shown that mutations can drastically alter the efficiency with which a population reproduces--and so, the rate at which it alters. It also demonstrates that evolution is slow-moving, a fact that some are unable to accept.
Another example of microevolution is the way mosquito genes that confer resistance to pesticides show up more often in populations where insecticides are used. This is because the use of pesticides causes a selective pressure that favors people who have resistant genotypes.
The speed at which evolution takes place has led to a growing awareness of its significance in a world shaped by human activities, including climate change, pollution, and the loss of habitats which prevent the species from adapting. Understanding evolution can help us make smarter decisions about the future of our planet and the life of its inhabitants.