The Academy's Evolution Site
Biology is a key 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 affects every area of scientific inquiry.
This site provides teachers, students 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, an ancient symbol, symbolizes the interconnectedness of all life. It appears in many religions and cultures as an emblem of unity and love. It also has many practical applications, such as providing a framework to understand the history of species and how they respond to changes in the environment.
Early attempts to represent the biological world were built on categorizing organisms based on their physical and metabolic characteristics. These methods, which depend on the collection of various 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 the diversity of bacterial species is greatly underrepresented3,4.
Genetic techniques have greatly expanded our ability to visualize the Tree of Life by circumventing the need for direct observation and experimentation. We can create trees using molecular methods, 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 especially true for microorganisms that are difficult to cultivate and are typically found in one sample5. A recent analysis of all genomes has produced an unfinished draft of the Tree of Life. This includes a large number of bacteria, archaea and other organisms that have not yet been identified or their diversity is not well understood6.
The expanded Tree of Life can be used to evaluate the biodiversity of a particular area and determine if specific habitats require special protection. The information is useful in a variety of ways, such as finding new drugs, fighting diseases and improving crops. This information is also extremely valuable for conservation efforts. It helps biologists discover areas most likely to be home to species that are cryptic, which could perform important metabolic functions and be vulnerable to human-induced change. While funding to protect biodiversity are essential, the best method to protect the world's biodiversity is to empower more people in developing countries with the information they require to act locally and support conservation.
Phylogeny
A phylogeny (also called an evolutionary tree) depicts the relationships between species. Using molecular data as well as morphological similarities and distinctions, or ontogeny (the process of the development of an organism), scientists can build an phylogenetic tree that demonstrates the evolutionary relationship between taxonomic categories. The concept of phylogeny is fundamental to understanding evolution, biodiversity and genetics.
A basic phylogenetic tree (see Figure PageIndex 10 Identifies the relationships between organisms that have similar traits and evolved from a common ancestor. These shared traits can be either analogous or homologous. Homologous traits share their evolutionary roots, while analogous traits look like they do, but don't have the identical origins. Scientists group similar traits together into a grouping referred to as a clade. For instance, all the organisms in a clade share the characteristic of having amniotic egg and evolved from a common ancestor who had eggs. The clades are then linked to form a phylogenetic branch that can determine the organisms with the closest relationship to.
For a more detailed and accurate phylogenetic tree scientists rely on molecular information from DNA or RNA to establish the relationships among organisms. This data is more precise than the morphological data and gives evidence of the evolutionary history of an organism or group. Researchers can utilize Molecular Data to calculate the age of evolution of organisms and determine the number of organisms that have an ancestor common to all.
The phylogenetic relationships of a species can be affected by a number of factors that include the phenotypic plasticity. This is a kind of behaviour that can change as a result of specific environmental conditions. This can cause a trait to appear more similar in one species than other species, which can obscure the phylogenetic signal. However, this problem can be reduced by the use of techniques like cladistics, which incorporate a combination of homologous and analogous features into the tree.
Additionally, phylogenetics can help predict the duration and rate of speciation. This information will assist conservation biologists in making choices about which species to protect from disappearance. In weblink , it is the preservation of phylogenetic diversity that will result in an ecosystem that is complete and balanced.
Evolutionary Theory
The main idea behind evolution is that organisms change over time as a result of their interactions with their environment. Many theories of evolution have been developed by a variety of scientists including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who envisioned an organism developing gradually according to 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 cause changes that could be passed on to offspring.
In the 1930s & 1940s, concepts from various fields, including natural selection, genetics & particulate inheritance, were brought together to form a modern evolutionary theory. This explains how evolution occurs by the variation in genes within a population and how these variations change with time due to natural selection. This model, known as genetic drift or mutation, gene flow, and sexual selection, is a key element of modern evolutionary biology and is mathematically described.
Recent developments in the field of evolutionary developmental biology have shown that genetic variation can be introduced into a species through genetic drift, mutation, and reshuffling of genes during sexual reproduction, and also through migration between populations. These processes, along with other ones like directional selection and gene erosion (changes in frequency of genotypes over time), can lead towards evolution. Evolution is defined as changes in the genome over time as well as changes in the phenotype (the expression of genotypes within individuals).
Students can gain a better understanding of phylogeny by incorporating evolutionary thinking into all areas of biology. A recent study by Grunspan and colleagues, for example demonstrated that teaching about the evidence for evolution increased students' understanding of evolution in a college biology class. For more details on how to teach evolution look up The Evolutionary Potency in All Areas of Biology or Thinking Evolutionarily: a Framework for Infusing Evolution into Life Sciences Education.
Evolution in Action
Scientists have studied evolution by looking in the past, studying fossils, and comparing species. They also study living organisms. Evolution is not a distant moment; it is a process that continues today. The virus reinvents itself to avoid new antibiotics and bacteria transform to resist antibiotics. Animals adapt their behavior because of the changing environment. The results are often evident.
It wasn't until late 1980s that biologists understood that natural selection could be observed in action as well. The key to this is that different traits result in the ability to survive at different rates and reproduction, and can be passed on from generation to generation.
In the past when one particular allele, the genetic sequence that defines color in a population of interbreeding species, it could quickly become more prevalent than all other alleles. In time, this could mean that the number of black moths in a population could increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
The ability to observe evolutionary change is much easier when a species has a fast generation turnover, as with bacteria. Since 1988, biologist Richard Lenski has been tracking twelve populations of E. Coli that descended from a single strain. samples from each population are taken every day and more than 50,000 generations have now been observed.
Lenski's research has demonstrated that mutations can alter the rate at which change occurs and the efficiency of a population's reproduction. 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 for pesticide resistance are more prevalent in areas where insecticides have been used. This is due to the fact that the use of pesticides creates a selective pressure that favors those with resistant genotypes.
The rapid pace at which evolution can take place has led to an increasing recognition of its importance in a world that is shaped by human activity, including climate change, pollution, and the loss of habitats that hinder many species from adapting. Understanding evolution can help you make better decisions about the future of our planet and its inhabitants.