The Academy's Evolution Site
Biological evolution is one of the most important concepts in biology. The Academies have been for a long time involved in helping those interested in science understand the theory of evolution and how it influences all areas of scientific research.
This site provides a range of sources for teachers, students as well as general readers about evolution. It has 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 appears in many cultures and spiritual beliefs as a symbol of unity and love. It also has important practical applications, such as providing a framework for understanding the evolution of species and how they respond to changes in the environment.
Early attempts to describe the biological world were based on categorizing organisms based on their physical and metabolic characteristics. These methods, which rely on the collection of various parts of organisms, or fragments of DNA, have significantly increased the diversity of a Tree of Life2. However the trees are mostly composed of eukaryotes; bacterial diversity remains vastly underrepresented3,4.
Genetic techniques have significantly expanded our ability to represent the Tree of Life by circumventing the requirement for direct observation and experimentation. Particularly, molecular methods enable us to create trees by using sequenced markers, such as the small subunit ribosomal gene.
Despite the massive growth of the Tree of Life through genome sequencing, a large amount of biodiversity remains to be discovered. This is particularly true of microorganisms, which are difficult to cultivate and are typically only present in a single sample5. A recent study 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 beneficial in assessing the biodiversity of an area, which can help to determine if specific habitats require protection. This information can be utilized in many ways, including identifying new drugs, combating diseases and improving crops. This information is also extremely beneficial to conservation efforts. It can help biologists identify areas that are likely to have species that are cryptic, which could have vital metabolic functions and be vulnerable to human-induced change. While conservation funds are important, the most effective method to preserve the world's biodiversity is to empower more people in developing nations with the necessary knowledge to take action locally and encourage conservation.
Phylogeny
A phylogeny, also known as an evolutionary tree, illustrates the connections between groups of organisms. Scientists can construct an phylogenetic chart which shows the evolution of taxonomic groups using molecular data and morphological similarities or differences. Phylogeny is crucial in understanding evolution, biodiversity and genetics.
A basic phylogenetic tree (see Figure PageIndex 10 Finds the connections between organisms with similar characteristics and have evolved from an ancestor with common traits. These shared traits could be either analogous or homologous. Homologous traits are identical in their evolutionary origins while analogous traits appear like they do, but don't have the same origins. Scientists group similar traits together into a grouping referred to as a Clade. For example, all of the organisms in a clade share the trait of having amniotic eggs and evolved from a common ancestor which had eggs. The clades then join to create a phylogenetic tree to identify organisms that have the closest connection to each other.
Scientists utilize molecular DNA or RNA data to build a phylogenetic chart that is more accurate and precise. This information is more precise and provides evidence of the evolution of an organism. Researchers can use Molecular Data to calculate the evolutionary age of organisms and identify how many species share an ancestor common to all.
The phylogenetic relationship can be affected by a number of factors such as the phenomenon of phenotypicplasticity. This is a kind of behavior that changes due to unique environmental conditions. This can cause a particular trait to appear more similar in one species than another, clouding the phylogenetic signal. This problem can be addressed by using cladistics, which incorporates the combination of homologous and analogous features in the tree.
In 무료에볼루션 , phylogenetics can help predict the length and speed of speciation. This information will assist conservation biologists in making decisions about which species to save from disappearance. Ultimately, it is the preservation of phylogenetic diversity that will result in an ecosystem that is complete and balanced.
Evolutionary Theory
The fundamental concept in evolution is that organisms alter over time because of their interactions with their environment. Many scientists have developed theories of evolution, such as the Islamic naturalist Nasir al-Din al-Tusi (1201-274), who believed that a living thing would develop according to its own needs as well as the Swedish taxonomist Carolus Linnaeus (1707-1778) who developed the modern hierarchical system of taxonomy, 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 and 1940s, ideas from a variety of fields--including genetics, natural selection and particulate inheritance - came together to form the current synthesis of evolutionary theory that explains how evolution happens 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 cornerstone of modern evolutionary biology and can be mathematically explained.
Recent developments in the field of evolutionary developmental biology have revealed that variation can be introduced into a species through mutation, genetic drift and reshuffling of genes in sexual reproduction, as well as through the movement of populations. These processes, as well as others like directional selection and genetic erosion (changes in the frequency of the genotype over time) can lead to evolution that is defined as changes in the genome of the species over time and also by changes in phenotype as time passes (the expression of the genotype in an individual).
Incorporating evolutionary thinking into all areas of biology education can increase students' understanding of phylogeny and evolution. A recent study by Grunspan and colleagues, for example, showed that teaching about the evidence that supports evolution increased students' understanding of evolution in a college biology class. For more information on how to teach about evolution, look up The Evolutionary Potential in All Areas of Biology and Thinking Evolutionarily: A Framework for Infusing Evolution into Life Sciences Education.
Evolution in Action
Scientists have traditionally studied evolution by looking in the past, studying fossils, and comparing species. They also observe living organisms. Evolution is not a distant event; it is an ongoing process. Viruses reinvent themselves to avoid new medications and bacteria mutate to resist antibiotics. Animals alter their behavior because of a changing environment. The changes that occur are often visible.
It wasn't until late 1980s that biologists began realize that natural selection was also in action. The main reason is that different traits can confer the ability to survive at different rates as well as reproduction, and may be passed on from one generation to the next.
In the past, if one allele - the genetic sequence that determines colour appeared in a population of organisms that interbred, it could be more prevalent than any other allele. Over time, this would mean that the number of moths with black pigmentation in a group may increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
It is easier to see evolutionary change when a species, such as bacteria, has a high generation turnover. Since 1988 the biologist Richard Lenski has been tracking twelve populations of E. coli that descended from a single strain. samples of each are taken on a regular basis and over 500.000 generations have been observed.
Lenski's work has demonstrated that a mutation can profoundly alter the rate at the rate at which a population reproduces, and consequently the rate at which it evolves. It also shows evolution takes time, which is hard for some to accept.
Microevolution can be observed in the fact that mosquito genes for resistance to pesticides are more prevalent in populations where insecticides are used. This is due to the fact that the use of pesticides creates a pressure that favors those 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 activities, including climate change, pollution, and the loss of habitats that prevent the species from adapting. Understanding evolution will help us make better decisions regarding the future of our planet as well as the life of its inhabitants.