So , You've Bought Evolution Site ... Now What?
The Academy's Evolution Site
Biological evolution is a central concept in biology. The Academies are committed to helping those interested in science comprehend the evolution theory and how it can be applied in all areas of scientific research.
This site offers a variety of resources for teachers, students, and general readers on evolution. It includes key video clip from NOVA and WGBH produced science programs on DVD.
Tree of Life
The Tree of Life is an ancient symbol of the interconnectedness of life. It is seen in a variety of spiritual traditions and cultures as symbolizing unity and love. It can be used in many practical ways in addition to providing a framework for understanding the history of species, and how they respond to changes in environmental conditions.
The earliest attempts to depict the world of biology focused on categorizing organisms into distinct categories which were distinguished by their physical and metabolic characteristics1. These methods are based on the collection of various parts of organisms or DNA fragments, have greatly 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.
By avoiding the need for direct observation and experimentation, genetic techniques have allowed us to represent the Tree of Life in a more precise manner. Particularly, molecular methods allow us to construct trees using sequenced markers such as the small subunit ribosomal gene.
Despite the rapid growth of the Tree of Life through genome sequencing, a large amount of biodiversity remains to be discovered. This is especially true of microorganisms that are difficult to cultivate and are often only represented in a single specimen5. Recent analysis of all genomes resulted in a rough draft of a Tree of Life. This includes a large number of archaea, bacteria, and other organisms that have not yet been isolated or their diversity is not well understood6.
The expanded Tree of Life can be used to determine the diversity of a specific area and determine if specific habitats require special protection. The information is useful in many ways, including finding new drugs, fighting diseases and improving crops. This information is also useful for conservation efforts. It can aid biologists in identifying areas that are most likely to have species that are cryptic, which could perform important metabolic functions, and could be susceptible to changes caused by humans. While funding to protect biodiversity are important, the most effective method to preserve the biodiversity of the world is to equip the people of developing nations with the necessary knowledge to take action locally and encourage conservation.
Phylogeny
A phylogeny (also known as an evolutionary tree) shows the relationships between different organisms. Scientists can build a phylogenetic diagram that illustrates the evolutionary relationship of taxonomic groups based on molecular data and morphological similarities or differences. 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 with similar traits that have evolved from common ancestors. These shared traits could be homologous, or analogous. Homologous traits are identical in their evolutionary origins while analogous traits appear similar but do not have the same origins. Scientists combine similar traits into a grouping known as a Clade. All members of a clade share a trait, such as amniotic egg production. They all came from an ancestor with these eggs. The clades are then connected to form a phylogenetic branch that can determine which organisms have the closest relationship to.
For a more detailed and accurate phylogenetic tree, scientists make use of molecular data from DNA or RNA to establish the relationships between organisms. This information is more precise and provides evidence of the evolution history of an organism. Researchers can utilize Molecular Data to calculate the evolutionary age of organisms and identify how many species share an ancestor common to all.
The phylogenetic relationships of organisms can be influenced by several factors, including phenotypic flexibility, an aspect of behavior that changes in response to specific environmental conditions. This can cause a particular trait to appear more similar in one species than another, obscuring the phylogenetic signal. This problem can be addressed by using cladistics, which is a a combination of homologous and analogous traits in the tree.
Additionally, phylogenetics aids determine the duration and rate at which speciation occurs. This information can help conservation biologists decide which species they should protect from the threat of extinction. It is ultimately the preservation of phylogenetic diversity that will lead to an ecologically balanced and complete ecosystem.
Evolutionary Theory
The central theme of evolution is that organisms acquire different features over time due to their interactions with their surroundings. Several theories of evolutionary change have been developed 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 in accordance with its requirements as well as the Swedish botanist Carolus Linnaeus (1707-1778) who designed the modern hierarchical taxonomy, as well as Jean-Baptiste Lamarck (1744-1829) who suggested that the use or misuse of traits causes changes that can be passed on to offspring.
In the 1930s and 1940s, concepts from a variety of fields -- including genetics, natural selection and particulate inheritance -- came together to form the current evolutionary theory synthesis 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, which incorporates mutations, genetic drift, gene flow and sexual selection can be mathematically described.
Recent discoveries in evolutionary developmental biology have shown how variations can be introduced to a species through genetic drift, mutations, reshuffling genes during sexual reproduction and the movement between populations. These processes, along with others like directional selection and genetic erosion (changes in the frequency of an individual's genotype over time) can lead to evolution which is defined by change in the genome of the species over time, and also by changes in phenotype as time passes (the expression of the genotype in an individual).
Students can better understand phylogeny by incorporating evolutionary thinking into all aspects of biology. In Read Significantly more by Grunspan and co. It was demonstrated that teaching students about the evidence for evolution increased their understanding of evolution during the course of a college biology. For more details on how to teach about evolution look up The Evolutionary Power of Biology in All Areas of Biology or Thinking Evolutionarily as a Framework for Integrating Evolution into Life Sciences Education.
Evolution in Action
Scientists have traditionally studied evolution through looking back in the past, analyzing fossils and comparing species. They also study living organisms. However, evolution isn't 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 are able to evade new medications and animals alter their behavior to a changing planet. The changes that occur are often apparent.
It wasn't until late 1980s that biologists understood that natural selection can be observed in action as well. The key is that various traits have different rates of survival and reproduction (differential fitness) and can be passed down from one generation to the next.
In the past, if a certain allele - the genetic sequence that determines colour - was found in a group of organisms that interbred, it might become more common than any other allele. Over time, that would mean that the number of black moths in a particular population could rise. 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, Richard Lenski, a biologist, has been tracking twelve populations of E.coli that descend from a single strain. Samples from each population were taken regularly and more than 500.000 generations of E.coli have passed.
Lenski's work has demonstrated that a mutation can profoundly alter the efficiency with the rate at which a population reproduces, and consequently, the rate at which it changes. It also proves that evolution takes time--a fact that some find hard to accept.
Microevolution is also evident in the fact that mosquito genes for pesticide resistance are more prevalent in areas where insecticides are used. 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 greater recognition of its importance particularly 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 can help us make smarter decisions regarding the future of our planet as well as the lives of its inhabitants.