The Academy's Evolution Site
The concept of biological evolution is among the most central concepts in biology. The Academies have been active for a long time in helping people who are interested in science understand the theory of evolution and how it influences all areas of scientific exploration.
This site provides a range of sources for students, teachers and general readers of evolution. It contains key video clips from NOVA and WGBH produced science programs on DVD.
Tree of Life
The Tree of Life is an ancient symbol that represents the interconnectedness of life. It is a symbol of love and unity across many cultures. It also has practical uses, like providing a framework to understand the evolution of species and how they react to changing environmental conditions.
Early attempts to describe the biological world were founded on categorizing organisms on their physical and metabolic characteristics. These methods, which rely on the sampling of different parts of organisms or fragments of DNA, have significantly increased the diversity of a Tree of Life2. These trees are mostly populated by eukaryotes, and bacteria are largely underrepresented3,4.
Genetic techniques have greatly broadened our ability to visualize the Tree of Life by circumventing the requirement for direct observation and experimentation. Trees can be constructed using molecular techniques, such as the small-subunit ribosomal gene.
The Tree of Life has been significantly expanded by genome sequencing. However, there is still much diversity to be discovered. This is particularly relevant to microorganisms that are difficult to cultivate, and which are usually only found in a single specimen5. A recent analysis of all genomes resulted in an initial draft of a Tree of Life. This includes a large number of archaea, bacteria, and other organisms that haven't yet been isolated or whose diversity has not been well understood6.
The expanded Tree of Life is particularly useful in assessing the diversity of an area, assisting to determine if specific habitats require protection. The information can be used in a variety of ways, from identifying the most effective remedies to fight diseases to enhancing the quality of crops. It is also beneficial for conservation efforts. It can aid biologists in identifying the areas most likely to contain cryptic species that could have important metabolic functions that could be vulnerable to anthropogenic change. While funding to protect biodiversity are important, the best way to conserve the world's biodiversity is to equip the people of developing nations with the necessary knowledge to take action locally and encourage conservation.
Phylogeny
A phylogeny (also known as an evolutionary tree) depicts the relationships between organisms. Scientists can construct a phylogenetic diagram that illustrates the evolution of taxonomic groups based on molecular data and morphological differences or similarities. Phylogeny is essential in understanding evolution, biodiversity and genetics.
A basic phylogenetic tree (see Figure PageIndex 10 ) identifies the relationships between organisms with similar traits that have evolved from common ancestors. These shared traits can be homologous, or analogous. Homologous traits are similar in their underlying evolutionary path, while analogous traits look similar, but do not share the identical origins. Scientists organize similar traits into a grouping called a the clade. All members of a clade have a common characteristic, like amniotic egg production. They all came from an ancestor with these eggs. A phylogenetic tree is constructed by connecting the clades to identify the organisms which are the closest to each other.
Scientists utilize molecular DNA or RNA data to build a phylogenetic chart that is more accurate and detailed. This data is more precise than morphological information and provides evidence of the evolution history of an individual or group. Researchers can utilize Molecular Data to estimate the age of evolution of living organisms and discover how many species share an ancestor common to all.
The phylogenetic relationship can be affected by a number of factors, including the phenotypic plasticity. This is a type of behaviour that can change in response to unique environmental conditions. This can cause a trait to appear more similar to one species than another, obscuring the phylogenetic signals. This problem can be addressed by using cladistics. This is a method that incorporates a combination of analogous and homologous features in the tree.
Furthermore, phylogenetics may help predict the time and pace of speciation. This information can assist conservation biologists in deciding which species to safeguard from the threat of extinction. In the end, it's the conservation of phylogenetic diversity that will lead to an ecosystem that is balanced and complete.
Evolutionary Theory
The fundamental concept in evolution is that organisms change over time as a result of their interactions with their environment. Several theories of evolutionary change have been developed by a wide range of scientists such as the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who believed that an organism would evolve slowly in accordance with its needs, the Swedish botanist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical taxonomy Jean-Baptiste Lamarck (1744-1829) who suggested that the use or non-use of traits causes changes that can be passed onto offspring.
In the 1930s and 1940s, theories from a variety of fields--including natural selection, genetics, and particulate inheritance -- came together to form the current synthesis of evolutionary theory, which defines how evolution is triggered by the variations of genes within a population, and how those variations change over time as a result of natural selection. This model, known as genetic drift mutation, gene flow, and sexual selection, is a key element of modern evolutionary biology and can be mathematically described.
에볼루션 슬롯 in the field of evolutionary developmental biology have demonstrated that variation can be introduced into a species through mutation, genetic drift, and reshuffling of genes during sexual reproduction, as well as through the movement of populations. These processes, as well as others such as directional selection or genetic erosion (changes in the frequency of an individual's genotype over time) can result in evolution, which is defined by change in the genome of the species over time, and also the change in phenotype over time (the expression of that genotype in an individual).
Students can better understand the concept of phylogeny through incorporating evolutionary thinking in all areas of biology. In a recent study conducted by Grunspan and co. It was found that teaching students about the evidence for evolution increased their understanding of evolution during a college-level course in biology. To learn more about how to teach about evolution, please read The Evolutionary Potential in All Areas of Biology and Thinking Evolutionarily: A Framework for Infusing Evolution in Life Sciences Education.
Evolution in Action
Traditionally, scientists have studied evolution through looking back, studying fossils, comparing species and observing living organisms. But evolution isn't a thing that occurred in the past, it's an ongoing process happening today. Bacteria evolve and resist antibiotics, viruses evolve and elude new medications and animals change their behavior to the changing climate. The changes that occur are often apparent.
It wasn't until the 1980s that biologists began to 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 an allele - the genetic sequence that determines colour was found in a group of organisms that interbred, it could be more common than any other allele. Over time, this would mean that the number of moths that have black pigmentation in a group may increase. 에볼루션 사이트 is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
It is easier to track evolution when the species, like bacteria, has a high generation turnover. Since 1988 biologist Richard Lenski has been tracking twelve populations of E. Coli that descended from a single strain. samples of each population are taken regularly, and over fifty thousand generations have passed.
Lenski's research has revealed that mutations can drastically alter the efficiency with which a population reproduces--and so the rate at which it alters. It also shows evolution takes time, a fact that is difficult for some to accept.
Microevolution can also be seen in the fact that mosquito genes that confer resistance to pesticides are more prevalent in populations where insecticides are used. Pesticides create an exclusive pressure that favors those with resistant genotypes.
The rapid pace at which evolution can take place has led to an increasing appreciation of its importance in a world shaped by human activities, including climate changes, pollution and the loss of habitats which prevent many species from adapting. Understanding the evolution process can help us make smarter decisions regarding the future of our planet and the lives of its inhabitants.