The Academy's Evolution Site
Biology is one of the most important concepts in biology. The Academies have been active for a long time in helping those interested in science comprehend the concept of evolution and how it influences all areas of scientific exploration.
This site offers a variety of tools for students, teachers as well as general readers about evolution. It also includes important video clips from NOVA and WGBH produced science programs on DVD.
Tree of Life
The Tree of Life, an ancient symbol, represents the interconnectedness of all life. It is a symbol of love and harmony in a variety of cultures. It also has many practical applications, like providing a framework for understanding the evolution of species and how they respond to changing environmental conditions.
The first attempts to depict the biological world were founded on categorizing organisms on their physical and metabolic characteristics. These methods, which relied on the sampling of various parts of living organisms or sequences of small DNA fragments, greatly increased the variety of organisms that could be included in the tree of life2. However these trees are mainly composed of eukaryotes; bacterial diversity is not represented in a large way3,4.
Genetic techniques have greatly expanded our ability to represent the Tree of Life by circumventing the need for direct observation and experimentation. Trees can be constructed using molecular techniques like the small-subunit ribosomal gene.
Despite the rapid expansion of the Tree of Life through genome sequencing, a lot of biodiversity remains to be discovered. This is especially true of microorganisms that are difficult to cultivate and are often only present in a single sample5. A recent study of all genomes known to date has created a rough draft of the Tree of Life, including numerous bacteria and archaea that have not been isolated, and whose diversity is poorly understood6.
This expanded Tree of Life is particularly beneficial in assessing the biodiversity of an area, which can help to determine if specific habitats require protection. The information is useful in many ways, including finding new drugs, fighting diseases and improving the quality of crops. This information is also valuable in conservation efforts. It helps biologists determine the areas most likely to contain cryptic species with important metabolic functions that could be at risk of anthropogenic changes. Although funding to protect biodiversity are crucial however, the most effective method to protect the world's biodiversity is for more people in developing countries to be equipped with the knowledge to act locally to promote conservation from within.
Phylogeny
A phylogeny, also known as an evolutionary tree, reveals the connections between various groups of organisms. Using molecular data, morphological similarities and differences or ontogeny (the process of the development of an organism) scientists can construct a phylogenetic tree which illustrates the evolution of taxonomic categories. The role of phylogeny is crucial in understanding biodiversity, genetics and evolution.
A basic phylogenetic Tree (see Figure PageIndex 10 Identifies the relationships between organisms with similar characteristics and have evolved from a common ancestor. These shared traits are either analogous or homologous. Homologous traits are identical in their underlying evolutionary path, while analogous traits look similar, but do not share the identical origins. Scientists group similar traits together into a grouping referred to as a the clade. For instance, all the organisms that make up a clade share the trait of having amniotic eggs and evolved from a common ancestor that had these eggs. A phylogenetic tree can be constructed by connecting the clades to identify the organisms which are the closest to one another.
Scientists use DNA or RNA molecular data to build a phylogenetic chart that is more accurate and precise. This information is more precise and gives evidence of the evolutionary history of an organism. Researchers can utilize Molecular Data to determine the evolutionary age of organisms and determine the number of organisms that share an ancestor common to all.
The phylogenetic relationships of a species can be affected by a variety of factors that include the phenomenon of phenotypicplasticity. This is a kind of behaviour that can change due to particular environmental conditions. This can cause a particular trait to appear more similar to one species than another, obscuring the phylogenetic signal. However, this problem can be cured by the use of techniques such as cladistics that include a mix of analogous and homologous features into the tree.
Additionally, phylogenetics can help predict the time and pace of speciation. This information can aid conservation biologists to make decisions about which species they should protect from extinction. In the end, it's the conservation of phylogenetic diversity that will result in an ecosystem that is complete and balanced.
Evolutionary Theory
The fundamental concept of evolution is that organisms acquire distinct characteristics over time due to their interactions with their environments. Many scientists have proposed theories of evolution, including the Islamic naturalist Nasir al-Din al-Tusi (1201-274), who believed that a living thing would evolve according to its own requirements and needs, the Swedish taxonomist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical taxonomy, as well as Jean-Baptiste Lamarck (1844-1829), who believed that the use or non-use of certain traits can result in changes that can be passed on to future generations.
In the 1930s and 1940s, theories from various fields, including genetics, natural selection, and particulate inheritance -- came together to form the current evolutionary theory which explains how evolution happens through the variation of genes within a population, and how those variants change in time as a result of natural selection. This model, known as genetic drift, mutation, gene flow and sexual selection, is a key element of current evolutionary biology, and is mathematically described.
Recent discoveries in evolutionary developmental biology have shown how variations can be introduced to a species by genetic drift, mutations or reshuffling of genes in sexual reproduction and migration between populations. These processes, along with 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 changes in the genome of the species over time, and also by changes in phenotype as time passes (the expression of that genotype within the individual).
Incorporating evolutionary thinking into all aspects of biology education could increase student understanding of the concepts of phylogeny and evolution. In a recent study by Grunspan and colleagues., it was shown that teaching students about the evidence for evolution boosted their acceptance of evolution during the course of a college biology. For more information about how to teach evolution, see 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 looked at evolution through the past, analyzing fossils and comparing species. They also study living organisms. Evolution is not a past event; it is an ongoing process. The virus reinvents itself to avoid new drugs and bacteria evolve to resist antibiotics. Animals alter their behavior as a result of the changing environment. The results are usually evident.
It wasn't until the 1980s when biologists began to realize that natural selection was also in action. The key to this is that different traits confer a different rate of survival as well as reproduction, and may be passed on from one generation to the next.
In the past, if one particular allele--the genetic sequence that controls coloration - was present in a group of interbreeding species, it could quickly become more common than all other alleles. In time, this could mean that the number of moths that have black pigmentation in a population could increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
It is easier to track evolution when a species, such as bacteria, has a high generation turnover. Since 1988, Richard Lenski, a biologist, has tracked twelve populations of E.coli that descend from one strain. Samples of each population have been collected frequently and more than 500.000 generations of E.coli have been observed to have passed.
Lenski's research has revealed that mutations can alter the rate at which change occurs and the effectiveness of a population's reproduction. It also proves that evolution takes time--a fact that some are unable to accept.
Another example of microevolution is the way mosquito genes that are resistant to pesticides appear more frequently in areas in which insecticides are utilized. evolutionkr is due to the fact that the use of pesticides causes a selective pressure that favors those with resistant genotypes.
The rapidity of evolution has led to a greater recognition of its importance, especially in a world which is largely shaped by human activities. This includes pollution, climate change, and habitat loss, which prevents many species from adapting. Understanding the evolution process will help us make better decisions about the future of our planet as well as the lives of its inhabitants.