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 permeates all areas of scientific exploration.
click the following article provides students, teachers and general readers with a variety of educational resources on evolution. It includes key video clip 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 used in many cultures and spiritual beliefs as a symbol of unity and love. It also has practical applications, like providing a framework to understand the history of species and how they respond to changes in the environment.
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 short DNA fragments, significantly increased the variety that could be represented in the tree of life2. However the trees are mostly made up of eukaryotes. Bacterial diversity is not represented in a large way3,4.
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 by using molecular methods like the small-subunit ribosomal gene.
The Tree of Life has been significantly expanded by genome sequencing. However, there is still much biodiversity to be discovered. This is particularly true of microorganisms that are difficult to cultivate and are often only represented in a single sample5. A recent analysis of all genomes known to date has produced a rough draft of the Tree of Life, including a large number of bacteria and archaea that have not been isolated, and whose diversity is poorly understood6.
The expanded Tree of Life can be used to determine the diversity of a particular area and determine if specific habitats need special protection. This information can be used in a range of ways, from identifying new remedies to fight diseases to enhancing the quality of crops. The information is also incredibly valuable to conservation efforts. It can help biologists identify areas that are most likely to have species that are cryptic, which could have vital metabolic functions and are susceptible to changes caused by humans. Although funds to safeguard biodiversity are vital however, the most effective method to protect the world's biodiversity is for more people in developing countries to be empowered with the necessary knowledge to act locally to promote conservation from within.
Phylogeny
A phylogeny, also known as an evolutionary tree, illustrates the relationships between various groups of organisms. By using molecular information as well as morphological similarities and distinctions, or ontogeny (the course of development of an organism), scientists can build an phylogenetic tree that demonstrates the evolutionary relationship between taxonomic groups. The role of phylogeny is crucial in understanding biodiversity, genetics and evolution.
A basic phylogenetic Tree (see Figure PageIndex 10 Finds the connections between organisms that have similar characteristics and have evolved from an ancestor that shared traits. These shared traits could be either homologous or analogous. Homologous traits are similar in their evolutionary journey. Analogous traits could appear like they are however they do not share the same origins. Scientists arrange similar traits into a grouping referred to as a clade. Every organism in a group share a characteristic, for example, amniotic egg production. They all derived from an ancestor that had these eggs. The clades are then connected to create a phylogenetic tree to determine which organisms have the closest relationship.
For a more precise and accurate phylogenetic tree scientists rely on molecular information from DNA or RNA to establish the relationships between organisms. This information is more precise and gives evidence of the evolution history of an organism. Researchers can use Molecular Data to estimate the evolutionary age of organisms and identify how many species share a common ancestor.
Phylogenetic relationships can be affected by a number of factors such as the phenotypic plasticity. This is a type behavior that changes as a result of unique environmental conditions. This can cause a characteristic to appear more similar to a species than another which can obscure the phylogenetic signal. However, this problem can be reduced by the use of techniques such as cladistics that incorporate a combination of homologous and analogous features into the tree.
Furthermore, phylogenetics may help predict the duration and rate of speciation. This information can help conservation biologists decide which species to protect from extinction. In the end, it's the conservation of phylogenetic diversity that will result in an ecosystem that is balanced and complete.
Evolutionary Theory
The central theme of evolution is that organisms acquire different features over time as a result of their interactions with their surroundings. A variety of theories about evolution have been proposed by a wide variety of scientists, including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who proposed that a living organism develop slowly according to its needs, the Swedish botanist Carolus Linnaeus (1707-1778) who developed modern hierarchical taxonomy, and Jean-Baptiste Lamarck (1744-1829) who suggested that the use or non-use of traits can cause changes that can be passed on to offspring.
In the 1930s and 1940s, theories from various fields, including genetics, natural selection, and particulate inheritance, came together to create a modern synthesis of evolution theory. This describes how evolution happens through the variation in genes within the population, and how these variations change with time due to natural selection. This model, which encompasses mutations, genetic drift in gene flow, and sexual selection can be mathematically described.
Recent discoveries in the field of evolutionary developmental biology have shown how variation can be introduced to a species via genetic drift, mutations, reshuffling genes during sexual reproduction and migration between populations. These processes, as well as others such as 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 better understand the concept of phylogeny by using evolutionary thinking into all aspects of biology. In a study by Grunspan et al. It was found that teaching students about the evidence for evolution boosted their understanding of evolution during a college-level course in biology. To find out 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--analyzing fossils, comparing species, and studying living organisms. Evolution is not a past moment; it is a process that continues today. The virus reinvents itself to avoid new drugs and bacteria evolve to resist antibiotics. Animals adapt their behavior in the wake of a changing world. The results are usually visible.
It wasn't until late 1980s that biologists began to realize that natural selection was in action. The key is that different characteristics result in different rates of survival and reproduction (differential fitness) and are passed from one generation to the next.
In the past, if a certain allele - the genetic sequence that determines color - appeared in a population of organisms that interbred, it might become more prevalent than any other allele. Over time, this would mean that the number of moths sporting black pigmentation in a group could increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
It is easier to see evolutionary change when the species, like bacteria, has a rapid generation turnover. 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 regularly and over 500.000 generations have been observed.
Lenski's research has revealed that mutations can drastically alter the efficiency with which a population reproduces and, consequently the rate at which it changes. It also shows evolution takes time, something that is difficult for some to accept.
Another example of microevolution is that mosquito genes that confer resistance to pesticides show up more often in populations in which insecticides are utilized. This is because the use of pesticides causes a selective pressure that favors those with resistant genotypes.
The rapidity of evolution has led to a greater appreciation 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 evolution will assist you in making better choices regarding the future of the planet and its inhabitants.