The Academy's Evolution Site
Biology is one of the most important concepts in biology. The Academies have been active for a long time in helping those interested in science comprehend the concept of evolution and how it permeates all areas of scientific research.
This site provides students, teachers and general readers with a variety of learning resources on evolution. It contains key video clips from NOVA and WGBH's science programs on DVD.
Tree of Life
The Tree of Life, an ancient symbol, represents the interconnectedness of all life. It is an emblem of love and unity across many cultures. It also has important practical uses, like providing a framework to understand the history of species and how they react to changes in the environment.
The earliest attempts to depict the biological world focused on the classification of organisms into distinct categories that were identified by their physical and metabolic characteristics1. These methods, which are based on the collection of various parts of organisms, or fragments of DNA, have greatly increased the diversity of a Tree of Life2. However the trees are mostly comprised of eukaryotes, and bacterial diversity is still largely unrepresented3,4.
Genetic techniques have significantly expanded our ability to represent the Tree of Life by circumventing the requirement for direct observation and experimentation. Particularly, molecular techniques enable us to create trees using sequenced markers, such as the small subunit ribosomal gene.
Despite the massive growth of the Tree of Life through genome sequencing, a lot of biodiversity awaits discovery. This is particularly the case for microorganisms which are difficult to cultivate and are typically found in one sample5. A recent analysis of all known genomes has produced a rough draft version of the Tree of Life, including a large number of bacteria and archaea that have not been isolated, and which are not well understood.
The expanded Tree of Life is particularly useful for assessing the biodiversity of an area, helping to determine if specific habitats require special protection. This information can be used in a variety of ways, from identifying new treatments to fight disease to enhancing crops. The information is also useful in conservation efforts. It can aid biologists in identifying those areas that are most likely contain cryptic species that could have significant metabolic functions that could be at risk from anthropogenic change. While conservation funds are important, the best method to preserve the world's biodiversity is to empower the people of developing nations with the necessary knowledge to act locally and promote conservation.
Phylogeny
A phylogeny (also called an evolutionary tree) depicts the relationships between organisms. Scientists can construct an phylogenetic chart which shows the evolutionary relationships between taxonomic categories using molecular information and morphological differences or similarities. The phylogeny of a tree plays an important role in understanding biodiversity, genetics and evolution.
A basic phylogenetic tree (see Figure PageIndex 10 ) identifies the relationships between organisms that share similar traits that have evolved from common ancestors. These shared traits may be analogous, or homologous. Homologous traits are similar in terms of their evolutionary path. Analogous traits might appear like they are, but they do not have the same origins. Scientists group similar traits into a grouping known as a Clade. All members of a clade share a characteristic, for example, amniotic egg production. They all came from an ancestor that had these eggs. A phylogenetic tree is then constructed by connecting the clades to identify the species that are most closely related to each other.
Scientists make use of DNA or RNA molecular information to build a phylogenetic chart which is more precise and precise. This information is more precise than the morphological data and provides evidence of the evolutionary history of an organism or group. Researchers can utilize Molecular Data to determine the age of evolution of organisms and determine how many organisms have the same ancestor.
에볼루션 슬롯 can be affected by a variety of factors such as the phenotypic plasticity. This is a type behavior that changes due to specific environmental conditions. This can cause a characteristic to appear more resembling to one species than to the other, obscuring the phylogenetic signals. However, Suggested Resource site can be reduced by the use of methods such as cladistics which include a mix of analogous and homologous features into the tree.
Additionally, phylogenetics aids determine the duration and speed of speciation. This information can assist conservation biologists make decisions about which species they should protect from the threat of extinction. In the end, it is the preservation of phylogenetic diversity which will create an ecosystem that is complete and balanced.
Evolutionary Theory
The central theme in evolution is that organisms change over time due to their interactions with their environment. Many theories of evolution have been proposed by a variety of scientists such as the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who envisioned an organism developing slowly according to its requirements, the Swedish botanist Carolus Linnaeus (1707-1778) who developed modern hierarchical taxonomy, and Jean-Baptiste Lamarck (1744-1829) who suggested that the use or misuse of traits cause changes that could be passed on to offspring.
In the 1930s and 1940s, concepts from a variety of fields--including genetics, natural selection and particulate inheritance - came together to form the current synthesis of evolutionary theory, which defines 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, which is known as genetic drift mutation, gene flow and sexual selection, is a key element of current evolutionary biology, and can be mathematically explained.
Recent discoveries in the field of evolutionary developmental biology have revealed that variations can be introduced into a species through mutation, genetic drift and reshuffling genes during sexual reproduction, as well as by migration between populations. These processes, as well as others like directional selection and genetic erosion (changes in the frequency of a genotype over time) can lead to evolution, which is defined by changes in the genome of the species over time, and also the change in phenotype as time passes (the expression of the genotype within the individual).
Incorporating evolutionary thinking into all areas of biology education could increase student understanding of the concepts of phylogeny as well as evolution. A recent study conducted by Grunspan and colleagues, for example demonstrated that teaching about the evidence for evolution helped students accept the concept of evolution in a college-level biology class. For more details about how to teach evolution read The Evolutionary Power of Biology in all Areas of Biology or Thinking Evolutionarily as a Framework for Infusing 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 occurred in the past. It's an ongoing process that is that is taking place in the present. Bacteria mutate and resist antibiotics, viruses evolve and escape new drugs and animals alter their behavior to the changing climate. The resulting changes are often visible.
It wasn't until late 1980s that biologists began to realize that natural selection was also in play. The key is that different characteristics result in different rates of survival and reproduction (differential fitness) and are transferred from one generation to the next.
In the past, if an allele - the genetic sequence that determines colour was present in a population of organisms that interbred, it could become more common than any other allele. In time, this could mean that 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.
It is easier to see evolution when the species, 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 frequently and more than 50,000 generations of E.coli have passed.
Lenski's research has revealed that a mutation can profoundly alter the efficiency with which a population reproduces--and so the rate at which it changes. It also demonstrates that evolution is slow-moving, a fact that some find difficult to accept.
Microevolution can also be seen in the fact that mosquito genes for resistance to pesticides are more prevalent in populations where insecticides have been used. Pesticides create an exclusive pressure that favors individuals who have resistant genotypes.
The rapidity of evolution has led to a greater recognition of its importance especially in a planet that is largely shaped by human activity. This includes pollution, climate change, and habitat loss that prevents many species from adapting. Understanding evolution will help us make better decisions about the future of our planet as well as the lives of its inhabitants.