The Academy's Evolution Site
The concept of biological evolution is a fundamental concept in biology. The Academies have been for a long time involved in helping people who are interested in science comprehend the theory of evolution and how it influences all areas of scientific research.
This site provides teachers, students and general readers with a variety of educational resources on evolution. It contains key video clips from NOVA and the WGBH-produced science programs on DVD.
Tree of Life
The Tree of Life is an ancient symbol of the interconnectedness of life. It is a symbol of love and unity in many cultures. It also has important practical applications, 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 world of biology focused on the classification of species into distinct categories that were distinguished by physical and metabolic characteristics1. These methods are based on the sampling of different parts of organisms or short DNA fragments, have significantly increased the diversity of a tree of Life2. However these trees are mainly comprised of eukaryotes, and bacterial diversity is still largely unrepresented3,4.
Genetic techniques have significantly expanded our ability to visualize the Tree of Life by circumventing the requirement for direct observation and experimentation. In particular, molecular methods enable us to create trees using sequenced markers, such as the small subunit ribosomal gene.
The Tree of Life has been significantly expanded by genome sequencing. However there is a lot of biodiversity to be discovered. This is especially true of microorganisms, which can be difficult to cultivate and are typically only found in a single sample5. A recent analysis of all genomes known to date has created a rough draft of the Tree of Life, including many bacteria and archaea that have not been isolated and which are not well understood.
This expanded Tree of Life can be used to assess the biodiversity of a particular area and determine if certain habitats require special protection. The information is useful in many ways, including finding new drugs, fighting diseases and improving the quality of crops. This information is also extremely beneficial in conservation efforts. It can help biologists identify areas that are likely to have cryptic species, which could perform important metabolic functions and be vulnerable to the effects of human activity. Although funding to safeguard biodiversity are vital however, the most effective method to protect the world's biodiversity is for more people 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 connections between groups of organisms. Scientists can construct a phylogenetic chart that shows the evolutionary relationship of taxonomic groups using molecular data 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 ) identifies the relationships between organisms with similar traits that evolved from common ancestral. These shared traits are either analogous or homologous. Homologous traits are identical in their evolutionary origins, while analogous traits look similar, but do not share the identical origins. Scientists group similar traits together into a grouping referred to as a Clade. All members of a clade share a characteristic, like amniotic egg production. They all evolved from an ancestor who had these eggs. A phylogenetic tree is then constructed by connecting clades to determine the organisms who are the closest to one another.
Scientists use DNA or RNA molecular data to construct a phylogenetic graph that is more accurate and detailed. This information is more precise and provides evidence of the evolutionary history of an organism. Molecular data allows researchers to determine the number of organisms who share an ancestor common to them and estimate their evolutionary age.
The phylogenetic relationships between organisms can be influenced by several factors, including phenotypic flexibility, a kind of behavior that changes in response to specific environmental conditions. This can cause a trait to appear more resembling to one species than to the other and obscure the phylogenetic signals. However, this problem can be solved through the use of techniques such as cladistics that combine homologous and analogous features into the tree.
Additionally, phylogenetics can help predict the length and speed of speciation. This information can assist conservation biologists decide the species they should safeguard from extinction. In the end, it is the conservation of phylogenetic diversity which will create an ecosystem that is complete and balanced.
Evolutionary Theory
The fundamental concept of evolution is that organisms acquire distinct characteristics over time due to their interactions with their environments. A variety of theories about evolution have been proposed by a wide variety of scientists, including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who proposed that a living organism develop slowly in accordance with its requirements, the Swedish botanist Carolus Linnaeus (1707-1778) who developed 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 & 1940s, theories from various fields, including genetics, natural selection and particulate inheritance, were brought together to form a contemporary theorizing of evolution. 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, known as genetic drift mutation, gene flow and sexual selection, is the foundation of modern evolutionary biology and is mathematically described.
Recent advances in the field of evolutionary developmental biology have revealed how variations can be introduced to a species by genetic drift, mutations and reshuffling of genes during sexual reproduction, and even migration between populations. These processes, along with other ones like directional selection and genetic erosion (changes in the frequency of the genotype over time) can lead to evolution, which is defined by changes in the genome of the species over time and the change in phenotype over time (the expression of the genotype in the individual).
Incorporating evolutionary thinking into all aspects of biology education could increase students' understanding of phylogeny and evolution. In a study by Grunspan et al., it was shown that teaching students about the evidence for evolution boosted their understanding of evolution in a college-level course in biology. For more information on how to teach evolution, see The Evolutionary Potency 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 by studying fossils, comparing species, and observing living organisms. However, evolution isn't something that occurred in the past, it's an ongoing process, happening in the present. Bacteria evolve and resist antibiotics, viruses reinvent themselves and escape new drugs and animals alter their behavior in response to a changing planet. The results are often visible.
It wasn't until late 1980s that biologists began realize that natural selection was at work. The key is that various characteristics result in different rates of survival and reproduction (differential fitness) and can be passed from one generation to the next.
In the past, if one allele - the genetic sequence that determines color - appeared in a population of organisms that interbred, it could become more prevalent than any other allele. In time, this could mean the number of black moths in a particular population could rise. 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 been tracking twelve populations of E.coli that descend from one strain. Samples from each population have been collected frequently and more than 500.000 generations of E.coli have passed.
Lenski's work has demonstrated that a mutation can dramatically alter the speed at the rate at which a population reproduces, and consequently, the rate at which it evolves. It also proves that evolution takes time--a fact that some people find difficult to accept.
에볼루션 슬롯게임 of microevolution is the way mosquito genes for resistance to pesticides show up more often in areas in which insecticides are utilized. That's because the use of pesticides creates a pressure that favors individuals with resistant genotypes.
The speed at which evolution takes place has led to an increasing recognition of its importance in a world shaped by human activity, including climate changes, pollution and the loss of habitats that hinder the species from adapting. Understanding the evolution process will help us make better choices about the future of our planet as well as the lives of its inhabitants.