The Academy's Evolution Site
The concept of biological evolution is among the most fundamental concepts in biology. The Academies are committed to helping those who are interested in the sciences comprehend the evolution theory and how it is incorporated throughout all fields of scientific research.
This site provides students, teachers and general readers with a variety of learning resources about evolution. It contains key video clips from NOVA and the WGBH-produced science programs on DVD.
Tree of Life
The Tree of Life is an ancient symbol that symbolizes the interconnectedness of all life. It is seen in a variety of spiritual traditions and cultures as a symbol of unity and love. It has many practical applications as well, including providing a framework to understand the history of species, and how they react to changing environmental conditions.
The first attempts to depict the biological world were founded on categorizing organisms on their metabolic and physical characteristics. These methods, which relied on the sampling of various parts of living organisms, or sequences of short fragments of their DNA greatly increased the variety of organisms that could be included in the tree of life2. The trees are mostly composed by eukaryotes and the diversity of bacterial species is greatly underrepresented3,4.
Genetic techniques have significantly expanded our ability to visualize the Tree of Life by circumventing the need for direct observation and experimentation. Trees can be constructed by 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 particularly relevant to microorganisms that are difficult to cultivate, and which are usually only found in one 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 useful in assessing the diversity of an area, which can help to determine whether specific habitats require special protection. The information is useful in a variety of ways, including finding new drugs, fighting diseases and enhancing crops. The information is also beneficial in conservation efforts. It can help biologists identify areas most likely to be home to species that are cryptic, which could perform important metabolic functions and are susceptible to the effects of human activity. While conservation funds are essential, the best method to preserve the world's biodiversity is to equip more people in developing nations with the necessary knowledge to act locally and promote conservation.
Phylogeny
A phylogeny (also known as an evolutionary tree) depicts the relationships between species. Using molecular data, morphological similarities and differences or ontogeny (the course of development of an organism) scientists can construct a phylogenetic tree that illustrates the evolutionary relationship between taxonomic groups. The phylogeny of a tree plays an important role in understanding biodiversity, genetics and evolution.
A basic phylogenetic Tree (see Figure PageIndex 10 Finds the connections between organisms that have similar traits and evolved from an ancestor with common traits. These shared traits could be analogous or homologous. Homologous traits share their underlying evolutionary path, while analogous traits look similar but do not have the same ancestors. Scientists arrange similar traits into a grouping called a the clade. For example, all of the organisms that make up a clade have the characteristic of having amniotic eggs. They evolved from a common ancestor which had these eggs. A phylogenetic tree is then constructed by connecting clades to determine the organisms that are most closely related to each other.
에볼루션 바카라 체험 utilize molecular DNA or RNA data to create a phylogenetic chart that is more accurate and precise. 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 an ancestor common to them and estimate their evolutionary age.
The phylogenetic relationship can be affected by a variety of factors such as the phenomenon of phenotypicplasticity. This is a type 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. However, this issue can be reduced by the use of methods like cladistics, which combine homologous and analogous features into the tree.
Additionally, phylogenetics can aid in predicting the length and speed of speciation. This information can help conservation biologists decide which species to protect from the threat of extinction. It is ultimately the preservation of phylogenetic diversity that will create an ecosystem that is complete and balanced.
Evolutionary Theory
The main idea behind evolution is that organisms change over time due to their interactions with their environment. 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 envisioned an organism developing slowly in accordance with its needs, the Swedish botanist Carolus Linnaeus (1707-1778) who designed the modern hierarchical taxonomy 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, concepts from a variety of fields--including natural selection, genetics, and particulate inheritance--came together to form the modern synthesis of evolutionary theory which explains how evolution occurs through the variation of genes within a population, and how those variations change in time due to natural selection. This model, which includes mutations, genetic drift as well as gene flow and sexual selection is mathematically described mathematically.
Recent advances in evolutionary developmental biology have revealed the ways in which variation can be introduced to a species by mutations, genetic drift and reshuffling of genes during sexual reproduction and migration between populations. These processes, along with other ones like directional selection and genetic erosion (changes in the frequency of a genotype over time) can result in evolution that is defined as 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 in all areas of biology. A recent study by Grunspan and colleagues, for example demonstrated that teaching about the evidence supporting evolution increased students' acceptance of evolution in a college-level biology course. To learn more about how to teach about evolution, see The Evolutionary Potential of all Areas of Biology and Thinking Evolutionarily A Framework for Infusing the Concept of Evolution into Life Sciences Education.
Evolution in Action
Traditionally, scientists have studied evolution by looking back--analyzing fossils, comparing species and observing living organisms. Evolution is not a past moment; it is an ongoing process. Bacteria transform and resist antibiotics, viruses re-invent themselves and elude new medications and animals alter their behavior in response to a changing planet. The results are usually easy to see.
It wasn't until the 1980s when biologists began to realize that natural selection was in play. The key is the fact that different traits can confer the ability to survive at different rates and reproduction, and they can be passed on from one generation to another.
In the past, if an allele - the genetic sequence that determines colour - was present in a population of organisms that interbred, it might become more prevalent than any other allele. In time, this could mean the number of black moths within the 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 see evolutionary change when a species, such as bacteria, has a rapid generation turnover. Since 1988, Richard Lenski, a biologist, has studied twelve populations of E.coli that are descended from a single strain. Samples from 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 at which a population reproduces. It also shows that evolution takes time, which is difficult for some to accept.
Microevolution can be observed in the fact that mosquito genes that confer resistance to pesticides are more common in populations where insecticides are used. 에볼루션 바카라 체험 is because pesticides cause an enticement that favors individuals who have resistant genotypes.
The speed of evolution taking place has led to an increasing recognition of its importance in a world shaped by human activities, including climate change, pollution and the loss of habitats which prevent the species from adapting. Understanding evolution can aid you in making better decisions about the future of our planet and its inhabitants.