The Academy's Evolution Site
Biology is a key concept in biology. The Academies are involved in helping those interested in science learn about the theory of evolution and how it is incorporated throughout all fields of scientific research.
This site provides teachers, students and general readers with a range of learning resources on evolution. It includes key video clip from NOVA and WGBH produced science programs on DVD.
에볼루션 바카라 사이트 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 also has important practical applications, like providing a framework to understand the history of species and how they respond to changing environmental conditions.
Early attempts to represent the biological world were founded on categorizing organisms on their physical and metabolic characteristics. These methods, based on sampling of different parts of living organisms or on sequences of small DNA fragments, greatly increased the variety of organisms that could be represented in a tree of life2. However, these trees are largely composed of eukaryotes; bacterial diversity remains vastly underrepresented3,4.
Genetic techniques have greatly expanded our ability to depict the Tree of Life by circumventing the requirement for direct observation and experimentation. Trees can be constructed using molecular methods such as the small subunit ribosomal gene.
Despite the dramatic expansion of the Tree of Life through genome sequencing, much biodiversity still is waiting to be discovered. This is especially true of microorganisms that are difficult to cultivate and are typically only present in a single sample5. A recent analysis of all genomes that are known has produced a rough draft version 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 useful for assessing the biodiversity of an area, assisting to determine whether specific habitats require protection. This information can be used in a variety of ways, from identifying new treatments to fight disease to enhancing the quality of crops. This information is also valuable in conservation efforts. It can aid biologists in identifying the areas most likely to contain cryptic species with important metabolic functions that may be at risk from anthropogenic change. While funds to safeguard biodiversity are vital, ultimately the best way to preserve the world's biodiversity is for more people 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, shows the connections between different groups of organisms. Scientists can construct a phylogenetic chart that shows the evolutionary relationships between taxonomic categories using molecular information and morphological similarities or differences. The phylogeny of a tree plays an important role in understanding the relationship between genetics, biodiversity and evolution.
A basic phylogenetic Tree (see Figure PageIndex 10 Identifies the relationships between organisms that have similar characteristics and have evolved from a common ancestor. These shared traits can be homologous, or analogous. Homologous traits are the same in their evolutionary journey. Analogous traits could appear like they are however they do not share the same origins. Scientists put similar traits into a grouping called a clade. For instance, all of the organisms in a clade share the characteristic of having amniotic eggs and evolved from a common ancestor which had these eggs. A phylogenetic tree is constructed by connecting the clades to identify the organisms which are the closest to one another.
To create a more thorough and precise phylogenetic tree scientists make use of molecular data from DNA or RNA to determine the relationships between organisms. This data is more precise than morphological data and provides evidence of the evolutionary history of an organism or group. The analysis of molecular data can help researchers identify the number of species that share a common ancestor and to estimate their evolutionary age.
Phylogenetic relationships can be affected by a variety of factors that include phenotypicplasticity. This is a kind of behavior that changes in response to specific environmental conditions. This can cause a trait to appear more like a species another, obscuring the phylogenetic signal. This problem can be addressed by using cladistics. This is a method that incorporates an amalgamation of analogous and homologous features in the tree.
Furthermore, phylogenetics may help predict the length and speed of speciation. This information can help conservation biologists decide the species they should safeguard from the threat of extinction. In the end, it is the preservation of phylogenetic diversity which will create an ecosystem that is balanced and complete.
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 proposed by a wide variety of scientists including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who envisioned an organism developing slowly according to its requirements, the Swedish botanist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical taxonomy Jean-Baptiste Lamarck (1744-1829) who suggested that the use or non-use of traits causes changes that can be passed onto offspring.
In the 1930s and 1940s, concepts from a variety of fields--including natural selection, genetics, and particulate inheritance - came together to form the modern evolutionary theory synthesis that explains how evolution happens through the variations of genes within a population and how these variants change in time due to natural selection. This model, which encompasses genetic drift, mutations as well as gene flow and sexual selection, can be mathematically described.
Recent discoveries in the field of evolutionary developmental biology have demonstrated how variations can be introduced to a species via mutations, genetic drift, reshuffling genes during sexual reproduction and the movement between populations. These processes, along with others, such as directional selection and gene erosion (changes in the frequency of genotypes over time) can result in evolution. Evolution is defined by changes in the genome over time as well as changes in phenotype (the expression of genotypes in an individual).
Incorporating evolutionary thinking into all areas of biology education can improve students' understanding of phylogeny as well as evolution. In a study by Grunspan et al. It was demonstrated that teaching students about the evidence for evolution boosted their understanding of evolution in a college-level course in biology. For more details on how to teach about evolution read The Evolutionary Potential in all Areas of Biology or Thinking Evolutionarily as a Framework for Infusing Evolution into Life Sciences Education.
Evolution in Action
Scientists have traditionally studied evolution by looking in the past, studying fossils, and comparing species. They also study living organisms. But evolution isn't just something that occurred in the past, it's an ongoing process that is taking place today. Bacteria mutate and resist antibiotics, viruses evolve and are able to evade new medications and animals change their behavior to a changing planet. The resulting changes are often visible.
It wasn't until late 1980s that biologists began to realize that natural selection was in play. The main reason is that different traits can confer an individual rate of survival and reproduction, and can be passed down from one generation to another.
In the past, if one particular allele, the genetic sequence that determines coloration--appeared in a population of interbreeding organisms, it might quickly become more prevalent than the other alleles. As time passes, this could mean that the number of moths with black pigmentation 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 the species, like bacteria, has a high generation turnover. 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 regularly and more than fifty thousand generations 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 evolves. It also shows that evolution takes time--a fact that some find difficult to accept.
Another example of microevolution is the way mosquito genes for resistance to pesticides are more prevalent in areas in which insecticides are utilized. Pesticides create an exclusive pressure that favors individuals who have resistant genotypes.
The speed at which evolution takes 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 which prevent many species from adjusting. Understanding the evolution process will help us make better choices about the future of our planet as well as the lives of its inhabitants.