The Academy's Evolution Site
Biology 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 every area of scientific inquiry.
This site provides teachers, students and general readers with a wide range of learning resources on 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, 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.
Early approaches to depicting the world of biology focused on separating organisms into distinct categories which had been distinguished by their physical and metabolic characteristics1. These methods are based on the collection of various parts of organisms or DNA fragments, have greatly increased the diversity of a tree of Life2. These trees are largely composed of eukaryotes, while bacterial diversity is vastly underrepresented3,4.
Genetic techniques have greatly broadened our ability to depict the Tree of Life by circumventing the need for direct observation and experimentation. Particularly, molecular techniques allow us to construct trees using sequenced markers like the small subunit of ribosomal RNA gene.
Despite the massive growth of the Tree of Life through genome sequencing, a lot of biodiversity remains to be discovered. This is especially true of microorganisms that are difficult to cultivate and are usually only present in a single specimen5. A recent analysis of all genomes produced an unfinished draft of the Tree of Life. This includes a wide range of bacteria, archaea and other organisms that have not yet been isolated, or the diversity of which is not well understood6.
The expanded Tree of Life is particularly useful in assessing the diversity of an area, helping to determine whether specific habitats require protection. The information is useful in a variety of ways, including finding new drugs, battling diseases and improving crops. 바카라 에볼루션 is also extremely useful in conservation efforts. It helps biologists determine those areas that are most likely contain cryptic species with significant metabolic functions that could be at risk of anthropogenic changes. While funding to protect biodiversity are essential, the best way to conserve the world's biodiversity is to empower the people of developing nations with the information they require to act locally and promote conservation.
Phylogeny
A phylogeny (also called an evolutionary tree) shows the relationships between different organisms. Utilizing molecular data similarities and differences in morphology, or ontogeny (the process of the development of an organism), scientists can build a phylogenetic tree which illustrates the evolution of taxonomic categories. Phylogeny is essential in understanding biodiversity, evolution and genetics.
A basic phylogenetic tree (see Figure PageIndex 10 Determines the relationship between organisms that have similar traits and have evolved from an ancestor that shared traits. These shared traits are either homologous or analogous. Homologous traits are similar in terms of their evolutionary paths. Analogous traits may look like they are, but they do not share the same origins. Scientists arrange similar traits into a grouping referred to as a clade. For instance, all the organisms in a clade share the trait of having amniotic eggs. They evolved from a common ancestor which had eggs. The clades then join to create a phylogenetic tree to determine the organisms with the closest relationship to.
To create a more thorough and accurate phylogenetic tree scientists rely on molecular information from DNA or RNA to identify the connections between organisms. This information is more precise than morphological information and provides evidence of the evolutionary background of an organism or group. The use of molecular data lets researchers determine the number of organisms that share the same ancestor and estimate their evolutionary age.
The phylogenetic relationships of a species can be affected by a variety of factors, including the phenotypic plasticity. This is a type of behavior that alters in response to specific environmental conditions. This can cause a particular trait to appear more similar in one species than another, obscuring the phylogenetic signal. This problem can be addressed by using cladistics, which incorporates an amalgamation of homologous and analogous features in the tree.
Additionally, phylogenetics aids determine the duration and speed of speciation. This information can assist conservation biologists in deciding which species to protect from the threat of extinction. It is ultimately the preservation of phylogenetic diversity which will result in an ecosystem that is complete and balanced.
Evolutionary Theory
The main idea behind evolution is that organisms alter over time because of their interactions with their environment. Many scientists have come up with theories of evolution, including the Islamic naturalist Nasir al-Din al-Tusi (1201-274), who believed that an organism would evolve according to its individual requirements, the Swedish taxonomist Carolus Linnaeus (1707-1778) who developed the modern taxonomy system that is hierarchical as well as Jean-Baptiste Lamarck (1844-1829), who believed that the usage or non-use of certain traits can result in changes that can be passed on to future generations.
In the 1930s and 1940s, ideas from a variety of fields -- including genetics, natural selection, and particulate inheritance - came together to create the modern synthesis of evolutionary theory which explains how evolution occurs through the variations of genes within a population and how those variations change in time as a result of natural selection. This model, called genetic drift or mutation, gene flow and sexual selection, is a cornerstone of current evolutionary biology, and can be mathematically explained.
Recent advances in evolutionary developmental biology have shown the ways in which variation can be introduced to a species by mutations, genetic drift, reshuffling genes during sexual reproduction, and even migration between populations. These processes, along with 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 and changes in the phenotype (the expression of genotypes in an individual).
Incorporating evolutionary thinking into all aspects of biology education could increase student understanding of the concepts of phylogeny as well as evolution. In a recent study by Grunspan and co. It was found that teaching students about the evidence for evolution boosted their understanding of evolution in an undergraduate biology course. For more information on how to teach evolution, see The Evolutionary Power of Biology in All Areas of Biology or Thinking Evolutionarily as a Framework for Integrating Evolution into Life Sciences Education.
Evolution in Action
Traditionally, scientists have studied evolution through studying fossils, comparing species, and observing living organisms. However, evolution isn't something that happened in the past; it's an ongoing process happening right now. Viruses reinvent themselves to avoid new antibiotics and bacteria transform to resist antibiotics. Animals alter their behavior as a result of the changing environment. The results are usually evident.
It wasn't until late 1980s that biologists realized that natural selection can be seen in action, as well. The key is the fact that different traits confer a different rate of survival and reproduction, and they can be passed on from generation to generation.
In the past, if one allele - the genetic sequence that determines colour - was present in a population of organisms that interbred, it could become more prevalent than any other allele. Over time, this would mean that the number of moths sporting black pigmentation in a 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 evolution when an organism, like bacteria, has a rapid generation turnover. Since 1988, Richard Lenski, a biologist, has tracked twelve populations of E.coli that descend from one strain. Samples from each population were taken regularly, and more than 50,000 generations of E.coli have been observed to have passed.
Lenski's work has shown that mutations can alter the rate at which change occurs and the rate at which a population reproduces. It also shows that evolution takes time, which is hard for some to accept.
Another example of microevolution is that mosquito genes that confer resistance to pesticides show up more often in populations in which insecticides are utilized. That's because the use of pesticides creates a pressure that favors individuals who have resistant genotypes.
The rapidity of evolution has led to an increasing appreciation of its importance particularly in a world which is largely shaped by human activities. This includes pollution, climate change, and habitat loss that hinders many species from adapting. Understanding evolution will aid you in making better decisions about the future of our planet and its inhabitants.