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The concept of biological evolution is a fundamental concept in biology. The Academies are committed to helping those who are interested in science comprehend the evolution theory and how it can be applied throughout all fields of scientific research.
This site provides a wide range of tools for teachers, students as well as general readers about evolution. It has important 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 all life. It is seen in a variety of religions and cultures as an emblem of unity and love. It can be used in many practical ways in addition to providing a framework to understand the history of species, and how they react to changing environmental conditions.
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 sampling of various parts of living organisms or sequences of small fragments of their DNA significantly expanded the diversity that could be included in the tree of life2. These trees are largely composed of eukaryotes, while the diversity of bacterial species is greatly underrepresented3,4.
Genetic techniques have greatly broadened our ability to depict the Tree of Life by circumventing the requirement for direct observation and experimentation. We can create trees using molecular techniques, such as the small-subunit ribosomal gene.
The Tree of Life has been dramatically expanded through genome sequencing. However, there is still much biodiversity to be discovered. This is particularly true for microorganisms that are difficult to cultivate and are often only represented in a single sample5. A recent analysis of all genomes produced an unfinished draft of the 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 thoroughly understood6.
The expanded Tree of Life is particularly useful in assessing the diversity of an area, assisting to determine whether specific habitats require special protection. This information can be used in a variety of ways, including finding new drugs, battling diseases and enhancing crops. This information is also extremely beneficial in conservation efforts. It can aid biologists in identifying the areas that are most likely to contain cryptic species that could have important metabolic functions that could be vulnerable to anthropogenic change. While funds to protect biodiversity are important, the best way to conserve the world's biodiversity is to equip more people in developing nations with the necessary knowledge to act locally and support conservation.
Phylogeny
A phylogeny (also called an evolutionary tree) shows the relationships between different organisms. Scientists can build a phylogenetic diagram that illustrates the evolution of taxonomic categories using molecular information and morphological similarities or differences. Phylogeny plays a crucial 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 ancestral. These shared traits may be homologous, or analogous. Homologous traits are the same in terms of their evolutionary journey. Analogous traits might appear like they are but they don't have the same ancestry. Scientists put similar traits into a grouping called a the clade. Every organism in a group have a common trait, such as amniotic egg production. They all derived from an ancestor that had these eggs. A phylogenetic tree can be built by connecting the clades to identify the organisms who are the closest to one another.
Scientists use molecular DNA or RNA data to create a phylogenetic chart that is more accurate and detailed. This information is more precise and gives evidence of the evolutionary history of an organism. Researchers can utilize Molecular Data to estimate the age of evolution of organisms and identify the number of organisms that have the same ancestor.
The phylogenetic relationships between species can be influenced by several factors, including phenotypic flexibility, an aspect of behavior that alters in response to unique environmental conditions. This can cause a characteristic to appear more like a species other species, which can obscure the phylogenetic signal. However, this problem can be cured by the use of methods like cladistics, which include a mix of similar and homologous traits into the tree.
Furthermore, phylogenetics may aid in predicting the duration and rate of speciation. This information can assist conservation biologists in making choices about which species to 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 in evolution is that organisms alter over time because of their interactions with their environment. Many scientists have come up with theories of evolution, such as the Islamic naturalist Nasir al-Din al-Tusi (1201-274) who believed that an organism could evolve according to its individual requirements, the Swedish taxonomist Carolus Linnaeus (1707-1778) who developed the modern hierarchical taxonomy, as well as Jean-Baptiste Lamarck (1844-1829), who suggested that the usage or non-use of traits can lead to changes that can be passed on to future generations.
In the 1930s & 1940s, theories from various areas, including genetics, natural selection and particulate inheritance, came together to form a contemporary theorizing of evolution. This defines how evolution is triggered by the variation in genes within a population and how these variations change with time due to natural selection. This model, which includes genetic drift, mutations in gene flow, and sexual selection can be mathematically described.
Recent developments in the field of evolutionary developmental biology have revealed that variations can be introduced into a species through mutation, genetic drift, and reshuffling of genes in sexual reproduction, as well as by migration between populations. These processes, as well as other ones like directionally-selected selection and erosion of genes (changes in frequency of genotypes over time) can lead to evolution. Evolution is defined as changes in the genome over time, as well as changes in phenotype (the expression of genotypes in an individual).
Incorporating evolutionary thinking into all areas of biology education can increase students' understanding of phylogeny and evolutionary. In a recent study by Grunspan and co. It was demonstrated 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, look up The Evolutionary Potential of all Areas of Biology and Thinking Evolutionarily: A Framework for Infusing Evolution in Life Sciences Education.
Evolution in Action
Scientists have looked at evolution through the past, studying fossils, and comparing species. They also study living organisms. However, evolution isn't something that occurred in the past. It's an ongoing process that is that is taking place today. Viruses evolve to stay away from new medications and bacteria mutate to resist antibiotics. Animals adapt their behavior in the wake of a changing world. The changes that result are often visible.
It wasn't until the late 1980s that biologists began to realize that natural selection was in action. The key is the fact that different traits can confer an individual rate of survival as well as reproduction, and may be passed on from one generation to another.
In the past, when one particular allele, the genetic sequence that controls coloration - was present in a group of interbreeding organisms, it could quickly become more prevalent than the other alleles. In time, this could mean that the number of moths that have black pigmentation may increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
Monitoring evolutionary changes in action is easier when a particular species has a rapid generation turnover like bacteria. 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 every day and over 50,000 generations have now passed.
Lenski's work has shown that mutations can alter the rate at which change occurs and the effectiveness at which a population reproduces. It also shows that evolution takes time, something that is difficult for some to accept.
Microevolution is also evident in the fact that mosquito genes that confer resistance to pesticides are more common in populations where insecticides are used. This is because the use of pesticides creates a selective pressure that favors individuals with resistant genotypes.
The rapid pace at which evolution takes place has led to an increasing awareness of its significance in a world shaped by human activity--including climate change, pollution, and the loss of habitats that prevent many species from adjusting. Understanding the evolution process will help us make better choices about the future of our planet, and the lives of its inhabitants.