The Academy's Evolution Site
Biology is a key concept in biology. The Academies have long been involved in helping those interested in science comprehend the concept of evolution and how it affects all areas of scientific research.
This site provides students, teachers and general readers with a variety of educational resources on evolution. It includes the most important video clips from NOVA and the 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 a symbol of love and harmony in a variety of cultures. It has many practical applications in addition to providing a framework for understanding the evolution of species and how they respond to changes in environmental conditions.
Early attempts to represent the biological world were based on categorizing organisms based on their metabolic and physical characteristics. These methods, which relied on the sampling of various parts of living organisms or short DNA fragments, significantly expanded the diversity that could be included in the tree of life2. However these trees are mainly composed of eukaryotes; bacterial diversity is still largely unrepresented3,4.
By avoiding the need for direct observation and experimentation genetic techniques have enabled us to represent the Tree of Life in a much more accurate way. We can construct trees using molecular techniques like the small-subunit ribosomal gene.
The Tree of Life has been greatly expanded thanks to genome sequencing. However, there is still much diversity to be discovered. This is particularly true for microorganisms, which are difficult to cultivate and are often only present in a single sample5. A recent study of all genomes that are known has created a rough draft of the Tree of Life, including many archaea and bacteria that have not been isolated, and which are not well understood.
The expanded Tree of Life can be used to assess the biodiversity of a specific region and determine if particular habitats need special protection. The information can be used in a range of ways, from identifying the most effective remedies to fight diseases to improving the quality of crops. This information is also extremely useful in conservation efforts. It can help biologists identify the areas that are most likely to contain cryptic species with significant metabolic functions that could be at risk of anthropogenic changes. While funds to protect biodiversity are essential however, the most effective method to protect the world's biodiversity is for more people living in developing countries to be empowered with the necessary knowledge to act locally to promote conservation from within.
Phylogeny
A phylogeny, also called an evolutionary tree, shows the connections between various groups of organisms. Using molecular data as well as morphological similarities and distinctions or ontogeny (the course of development of an organism), scientists can build a phylogenetic tree which illustrates the evolution of taxonomic categories. The phylogeny of a tree plays an important role in understanding biodiversity, genetics and evolution.
A basic phylogenetic Tree (see Figure PageIndex 10 ) determines the relationship between organisms that share similar traits that evolved from common ancestral. These shared traits may be homologous, or analogous. Homologous traits are similar in their evolutionary origins and analogous traits appear similar but do not have the same ancestors. Scientists put similar traits into a grouping referred to as a Clade. All members of a clade share a trait, such as amniotic egg production. They all evolved from an ancestor that had these eggs. The clades are then connected to form a phylogenetic branch to determine the organisms with the closest relationship to.
To create a more thorough and accurate phylogenetic tree, scientists rely on molecular information from DNA or RNA to identify the connections between organisms. This data is more precise than the morphological data and gives evidence of the evolutionary history of an individual or group. The use of molecular data lets researchers identify the number of species that have the same ancestor and estimate their evolutionary age.
The phylogenetic relationships of a species can be affected by a number of factors, including the phenotypic plasticity. This is a kind of behavior that alters due to specific environmental conditions. This can cause a trait to appear more similar to a species than to another, obscuring the phylogenetic signals. please click for source can be addressed by using cladistics, which incorporates an amalgamation of homologous and analogous features in the tree.
Additionally, phylogenetics can help predict the time and pace of speciation. This information can assist conservation biologists in making choices about which species to save from 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 of evolution is that organisms acquire various characteristics over time based on their interactions with their surroundings. 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 individual requirements and needs, the Swedish taxonomist Carolus Linnaeus (1707-1778) who conceived the modern taxonomy system that is hierarchical as well as Jean-Baptiste Lamarck (1844-1829), who suggested that the use or non-use of traits can cause changes that can be passed on to future generations.
In the 1930s and 1940s, ideas from different fields, including genetics, natural selection and particulate inheritance, were brought together to form a contemporary synthesis of evolution theory. This defines how evolution occurs by the variations in genes within a population and how these variations change with time due to natural selection. This model, which incorporates genetic drift, mutations as well as gene flow and sexual selection is mathematically described mathematically.
Recent discoveries in the field of evolutionary developmental biology have shown the ways in which variation can be introduced to a species via mutations, genetic drift, reshuffling genes during sexual reproduction and migration between populations. These processes, as well as others like directional selection and genetic erosion (changes in the frequency of an individual's genotype over time) can lead to evolution that is defined as change in the genome of the species over time and also by changes in phenotype as time passes (the expression of the genotype in the individual).
Students can better understand the concept of phylogeny through incorporating evolutionary thinking in all areas of biology. A recent study by Grunspan and colleagues, for example revealed that teaching students about the evidence that supports evolution increased students' understanding of evolution in a college-level biology course. For more information on how to teach evolution read The Evolutionary Potential in all Areas of Biology or Thinking Evolutionarily as a Framework for Infusing Evolution into Life Sciences Education.
Evolution in Action
Traditionally scientists have studied evolution through looking back, studying fossils, comparing species and observing living organisms. Evolution is not a distant moment; it is an ongoing process that continues to be observed today. Bacteria evolve and resist antibiotics, viruses reinvent themselves and escape new drugs, and animals adapt their behavior in response to a changing planet. The changes that occur are often apparent.
It wasn't until late 1980s when biologists began to realize that natural selection was also at work. The key to this is that different traits confer a different rate of survival as well as reproduction, and may be passed on from generation to generation.
In the past, if one allele - the genetic sequence that determines colour was found in a group of organisms that interbred, it could become more common than other allele. In time, this could mean that the number of moths with black pigmentation could 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 much easier when a species has a rapid turnover of its generation like bacteria. Since 1988, Richard Lenski, a biologist, has been tracking twelve populations of E.coli that descend from one strain. Samples of each population have been collected regularly, and more than 50,000 generations of E.coli have been observed to have passed.
Lenski's research has shown 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 demonstrates that evolution takes time, a fact that some find difficult to accept.
Microevolution can be observed in the fact that mosquito genes that confer resistance to pesticides are more prevalent in areas that have used insecticides. This is due to the fact that the use of pesticides creates a pressure that favors individuals who have resistant genotypes.
The rapidity of evolution has led to a growing recognition 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 evolution will assist you in making better choices about the future of our planet and its inhabitants.