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 understand the concept of evolution and how it permeates all areas of scientific exploration.
This site provides a range of tools for teachers, students, and general readers on evolution. It contains important video clips from NOVA and WGBH-produced science programs on DVD.
Tree of Life
The Tree of Life is an ancient symbol of the interconnectedness of life. It appears in many cultures and spiritual beliefs as an emblem of unity and love. It has numerous practical applications as well, such as providing a framework to understand the evolution of species and how they react to changes in environmental conditions.
The earliest attempts to depict the biological world focused on separating species into distinct categories that were identified by their physical and metabolic characteristics1. These methods, based on sampling of different parts of living organisms or small fragments of their DNA greatly increased the variety of organisms that could be represented in a tree of life2. The trees are mostly composed by eukaryotes, and bacterial diversity is vastly underrepresented3,4.
In avoiding the necessity of direct observation and experimentation genetic techniques have enabled us to depict the Tree of Life in a more precise manner. We can construct trees using molecular techniques, such as the small-subunit ribosomal gene.
Despite the massive expansion of the Tree of Life through genome sequencing, a lot of biodiversity remains to be discovered. This is particularly true for microorganisms that are difficult to cultivate and are usually only found in a single sample5. A recent analysis of all genomes produced a rough draft of the Tree of Life. This includes a wide range of archaea, bacteria and other organisms that haven't yet been isolated or the diversity of which is not thoroughly understood6.
This expanded Tree of Life is particularly useful in assessing the diversity of an area, assisting to determine if certain habitats require special protection. This information can be utilized in a variety of ways, such as identifying new drugs, combating diseases and improving crops. This information is also extremely useful in conservation efforts. It can help biologists identify areas that are most likely to have species that are cryptic, which could perform important metabolic functions and are susceptible to the effects of human activity. While funds to protect biodiversity are essential, the best method to preserve the biodiversity of the world is to equip the people of developing nations with the knowledge they need to take action locally and encourage conservation.
Phylogeny
A phylogeny (also known as an evolutionary tree) shows the relationships between organisms. Scientists can construct a phylogenetic chart that shows the evolution of taxonomic categories using molecular information 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 ) determines the relationship between organisms with similar traits that have evolved from common ancestors. These shared traits may be analogous or homologous. 에볼루션바카라사이트 share their underlying evolutionary path and analogous traits appear similar but do not have the same origins. Scientists combine similar traits into a grouping referred to as a the clade. All organisms in a group have a common characteristic, like amniotic egg production. They all came from an ancestor who had these eggs. A phylogenetic tree can be constructed by connecting the clades to identify the species that are most closely related to one another.
To create a more thorough and accurate phylogenetic tree, scientists make use of molecular data from DNA or RNA to determine the connections between organisms. This information is more precise and provides evidence of the evolution history of an organism. Molecular data allows researchers to determine the number of organisms who share the same ancestor and estimate their evolutionary age.
The phylogenetic relationships between organisms can be affected by a variety of factors including phenotypic plasticity, an aspect of behavior that changes in response to unique environmental conditions. This can cause a trait to appear more similar to one species than to another and obscure the phylogenetic signals. However, this issue can be reduced by the use of techniques such as cladistics which include a mix of similar and homologous traits into the tree.
Additionally, phylogenetics aids determine the duration and rate at which speciation takes place. This information can assist conservation biologists in making choices about which species to safeguard from extinction. In the end, it's the conservation of phylogenetic variety that will lead to 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 proposed theories of evolution, such as the Islamic naturalist Nasir al-Din al-Tusi (1201-274), who believed that an organism would evolve according to its own needs as well as 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 use or non-use of traits can lead to changes that can be passed on to future generations.
In the 1930s & 1940s, theories from various fields, including natural selection, genetics & particulate inheritance, merged to create a modern theorizing of evolution. This defines how evolution happens through the variations in genes within the population and how these variants change with time due to natural selection. This model, which includes genetic drift, mutations as well as gene flow and sexual selection, can be mathematically described.
Recent discoveries in the field of evolutionary developmental biology have shown the ways in which variation can be introduced to a species through genetic drift, mutations, reshuffling genes during sexual reproduction and the movement between populations. These processes, along with other ones like directional selection and genetic erosion (changes in the frequency of the genotype over time) can result in evolution, which is defined by changes in the genome of the species over time and also by changes in phenotype as time passes (the expression of that genotype in the individual).
Students can better understand the concept of phylogeny by using evolutionary thinking in all areas of biology. A recent study conducted by Grunspan and colleagues, for example revealed that teaching students about the evidence that supports evolution increased students' acceptance of evolution in a college-level biology class. For more details on how to teach about evolution look up The Evolutionary Potential in all Areas of Biology or Thinking Evolutionarily: a Framework for Integrating Evolution into Life Sciences Education.
Evolution in Action
Traditionally scientists have studied evolution by looking back--analyzing fossils, comparing species and studying living organisms. However, evolution isn't something that occurred in the past. It's an ongoing process, happening right now. Bacteria mutate and resist antibiotics, viruses reinvent themselves and are able to evade new medications and animals change their behavior to a changing planet. The changes that result are often evident.
It wasn't until late 1980s that biologists began realize that natural selection was in action. The main reason is that different traits result in the ability to survive at different rates as well as reproduction, and may be passed down from generation to generation.
In the past, if one allele - the genetic sequence that determines color - appeared in a population of organisms that interbred, it might become more common than any other allele. As time passes, that could mean that the number of black moths within 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 the species, like bacteria, has a rapid generation turnover. Since 1988 biologist Richard Lenski has been tracking twelve populations of E. bacteria that descend from a single strain; samples from each population are taken every day and over fifty thousand generations have passed.
Lenski's research has demonstrated 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--a fact that some people find difficult to accept.
Microevolution can be observed in the fact that mosquito genes for resistance to pesticides are more common in populations where insecticides have been used. This is due to the fact that the use of pesticides creates a selective pressure that favors those with resistant genotypes.
The rapidity of evolution has led to a growing appreciation of its importance, especially in a world that is largely shaped by human activity. This includes pollution, climate change, and habitat loss that hinders many species from adapting. Understanding the evolution process can help you make better decisions about the future of our planet and its inhabitants.