The Academy's Evolution Site
Biology is one of the most fundamental concepts in biology. The Academies are involved in helping those who are interested in the sciences comprehend the evolution theory and how it is permeated throughout all fields of scientific research.
This site provides teachers, students and general readers with a variety of educational resources on evolution. It contains 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 is seen in a variety of religions and cultures as symbolizing unity and love. It has many practical applications as well, such as providing a framework to understand the evolution of species and how they react to changes in environmental conditions.
The first attempts to depict the world of biology were founded on categorizing organisms on their metabolic and physical characteristics. These methods, which rely on the sampling of different parts of living organisms, or sequences of small fragments of their DNA, greatly increased the variety of organisms that could be represented in a tree of life2. The trees are mostly composed of eukaryotes, while bacteria are largely underrepresented3,4.
Genetic techniques have significantly expanded our ability to visualize the Tree of Life by circumventing the need for direct observation and experimentation. Particularly, molecular methods allow us to build trees by using sequenced markers, such as the small subunit ribosomal RNA gene.
Despite the rapid expansion of the Tree of Life through genome sequencing, a lot of biodiversity is waiting to be discovered. This is particularly the case for microorganisms which are difficult to cultivate and which are usually only found in a single specimen5. 에볼루션 코리아 of all genomes known to date has produced a rough draft version of the Tree of Life, including numerous bacteria and archaea that have not been isolated, and which are not well understood.
This expanded Tree of Life is particularly useful for assessing the biodiversity of an area, helping to determine if certain habitats require special protection. This information can be used in a variety of ways, from identifying new treatments to fight disease to improving crop yields. This information is also extremely useful in conservation efforts. It can aid biologists in identifying the areas that are most likely to contain cryptic species with important metabolic functions that may be at risk from anthropogenic change. Although funding to safeguard biodiversity are vital, ultimately the best way to ensure the preservation of biodiversity around the world is for more people living in developing countries to be equipped with the knowledge to take action locally to encourage conservation from within.
Phylogeny
A phylogeny (also called an evolutionary tree) illustrates the relationship between different organisms. Using molecular data, morphological similarities and differences or ontogeny (the course of development of an organism), scientists can build a phylogenetic tree that illustrates the evolutionary relationship between taxonomic categories. Phylogeny is essential in understanding biodiversity, evolution and genetics.
A basic phylogenetic Tree (see Figure PageIndex 10 Identifies the relationships between organisms with similar characteristics and have evolved from an ancestor with common traits. These shared traits can be homologous, or analogous. Homologous traits are similar in their evolutionary roots, while analogous traits look similar but do not have the same origins. Scientists combine similar traits into a grouping called a Clade. Every organism in a group share a trait, such as amniotic egg production. They all came from an ancestor who had these eggs. A phylogenetic tree can be constructed by connecting the clades to identify the species that are most closely related to one another.
For a more precise and precise phylogenetic tree scientists use molecular data from DNA or RNA to establish the relationships between organisms. This information is more precise and provides evidence of the evolutionary history of an organism. The use of molecular data lets researchers identify the number of organisms who share a common ancestor and to estimate their evolutionary age.
The phylogenetic relationships of organisms are influenced by many factors, including phenotypic plasticity a kind of behavior that alters in response to unique environmental conditions. This can make a trait appear more similar to one species than another which can obscure the phylogenetic signal. However, this problem can be reduced by the use of methods such as cladistics which incorporate a combination of homologous and analogous features into the tree.
Additionally, phylogenetics can help predict the duration and rate at which speciation takes place. This information can aid conservation biologists in making decisions about which species to protect from the threat of extinction. In the end, it's the conservation of phylogenetic diversity which will create an ecosystem that is complete and balanced.
Evolutionary Theory
The main idea behind evolution is that organisms acquire various characteristics over time based on their interactions with their environment. A variety of theories about evolution have been developed by a wide variety of scientists such as the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who proposed that a living organism develop gradually 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 causes changes that could be passed on to offspring.
In the 1930s and 1940s, ideas from different fields, such as genetics, natural selection, and particulate inheritance, were brought together to form a contemporary theorizing of evolution. This describes how evolution is triggered by the variation in genes within the population and how these variants alter over time due to natural selection. This model, called genetic drift mutation, gene flow and sexual selection, is a cornerstone of modern evolutionary biology and can be mathematically described.
Recent discoveries in the field of evolutionary developmental biology have demonstrated that genetic variation can be introduced into a species via genetic drift, mutation, and reshuffling genes during sexual reproduction, as well as through the movement of populations. These processes, as well as others such as the directional selection process and the erosion of genes (changes in the frequency of genotypes over time) can lead to evolution. Evolution is defined by changes in the genome over time, as well as changes in phenotype (the expression of genotypes within individuals).
Students can better understand phylogeny by incorporating evolutionary thinking in all areas of biology. In a recent study by Grunspan et al., it was shown that teaching students about the evidence for evolution boosted their understanding of evolution in the course of a college biology. For more information on 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
Traditionally scientists have studied evolution through looking back--analyzing fossils, comparing species and studying living organisms. But evolution isn't just something that happened in the past, it's an ongoing process that is happening right now. Bacteria evolve and resist antibiotics, viruses re-invent themselves and escape new drugs and animals alter their behavior to a changing planet. The resulting changes are often easy to see.
It wasn't until the late 1980s when biologists began to realize that natural selection was also in action. The main reason is that different traits confer a different rate of survival and reproduction, and they can be passed down from one generation to another.
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 any other allele. As time passes, this could mean that the number of moths sporting black pigmentation in a group may increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
It is easier to track evolutionary change when an organism, like bacteria, has a high generation turnover. Since 1988, Richard Lenski, a biologist, has been tracking twelve populations of E.coli that descend from a single strain. The samples of each population have been taken regularly and more than 50,000 generations of E.coli have passed.
Lenski's research has shown that a mutation can dramatically alter the rate at which a population reproduces and, consequently the rate at which it changes. It also demonstrates that evolution takes time, a fact that is difficult for some to accept.
Another example of microevolution is that mosquito genes that are resistant to pesticides appear more frequently in populations where insecticides are employed. This is due to pesticides causing an enticement that favors individuals who have resistant genotypes.
The speed at which evolution can take place has led to an increasing recognition of its importance in a world shaped by human activity, including climate change, pollution, and the loss of habitats that hinder the species from adapting. Understanding evolution can aid you in making better decisions about the future of our planet and its inhabitants.