The Advanced Guide To Evolution Site
The Academy's Evolution Site
Biological evolution is one of the most important concepts in biology. The Academies are committed to helping those interested in the sciences comprehend the evolution theory and how it is incorporated across all areas of scientific research.
This site provides teachers, students and general readers with a wide range of learning resources on evolution. It includes important video clips from NOVA and WGBH-produced science programs on DVD.
Tree of Life
The Tree of Life is an ancient symbol of the interconnectedness of all life. 에볼루션 바카라 무료 is a symbol of love and unity in many cultures. It can be used in many practical ways as well, such as providing a framework to understand the history of species, and how they respond to changes in environmental conditions.
Early attempts to describe the biological world were built on categorizing organisms based on their physical and metabolic characteristics. These methods, based on sampling of different parts of living organisms or on short fragments of their DNA significantly expanded the diversity that could be represented in the tree of life2. These trees are mostly populated of eukaryotes, while bacteria are largely underrepresented3,4.
Genetic techniques have greatly 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 using sequenced markers such as the small subunit of ribosomal RNA gene.
The Tree of Life has been greatly expanded thanks to genome sequencing. However there is a lot of diversity to be discovered. This is particularly true of microorganisms, which are difficult to cultivate and are usually only found in a single sample5. A recent study of all genomes that are known has produced a rough draft of the Tree of Life, including numerous bacteria and archaea that are not isolated and which are not well understood.
The expanded Tree of Life is particularly useful in assessing the diversity of an area, helping to determine if certain habitats require protection. The information is useful in many ways, including finding new drugs, battling diseases and improving crops. This information is also extremely valuable to conservation efforts. It can aid biologists in identifying the areas most likely to contain cryptic species with potentially important metabolic functions that could be at risk of anthropogenic changes. While conservation funds are important, the best method to protect the biodiversity of the world is to equip more people in developing countries with the necessary knowledge to act locally and promote conservation.
Phylogeny
A phylogeny, also known as an evolutionary tree, reveals the relationships between groups of organisms. Utilizing molecular data, morphological similarities and differences or ontogeny (the process of the development of an organism), scientists can build a phylogenetic tree which illustrates the evolution of taxonomic categories. Phylogeny plays a crucial role in understanding biodiversity, genetics and evolution.
A basic phylogenetic tree (see Figure PageIndex 10 Identifies the relationships between organisms with similar traits and have evolved from an ancestor that shared traits. These shared traits could be analogous, or homologous. Homologous traits share their evolutionary roots, while analogous traits look similar, but do not share the same origins. Scientists arrange similar traits into a grouping called a clade. All members of a clade have a common characteristic, for example, amniotic egg production. They all came from an ancestor with these eggs. The clades are then linked to form a phylogenetic branch that can determine which organisms have the closest connection to each other.
Scientists use DNA or RNA molecular data to create a phylogenetic chart which is more precise and precise. This information is more precise and provides evidence of the evolutionary history of an organism. The use of molecular data lets researchers determine the number of organisms that share a common ancestor and to estimate their evolutionary age.
Phylogenetic relationships can be affected by a variety of factors such as the phenotypic plasticity. This is a kind of behavior that alters as a result of unique environmental conditions. This can cause a trait to appear more similar to one species than another and obscure the phylogenetic signals. This problem can be mitigated by using cladistics. This is a method that incorporates the combination of analogous and homologous features in the tree.
In addition, phylogenetics can help predict the duration and rate of speciation. This information can aid conservation biologists to decide which species to protect from extinction. Ultimately, it is the preservation of phylogenetic diversity that will lead to an ecosystem that is complete and balanced.
Evolutionary Theory
The fundamental concept in evolution is that organisms alter over time because of their interactions with their environment. Several theories of evolutionary change have been proposed by a wide variety of scientists such as 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 conceived the modern hierarchical taxonomy Jean-Baptiste Lamarck (1744-1829) who suggested that the use or misuse of traits causes changes that could be passed onto offspring.
In the 1930s and 1940s, ideas from a variety of fields--including genetics, natural selection and particulate inheritance--came together to form the current evolutionary theory, which defines how evolution is triggered by the variations of genes within a population and how these variants change in time as a result of natural selection. This model, known as genetic drift, mutation, gene flow, and sexual selection, is a key element of the current evolutionary biology and can be mathematically described.
Recent discoveries in the field of evolutionary developmental biology have shown that variation can be introduced into a species via genetic drift, mutation, and reshuffling of genes in sexual reproduction, as well as by migration between populations. These processes, as well as other ones like directional selection and genetic erosion (changes in the frequency of a 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 over time (the expression of that genotype within the individual).
Students can better understand phylogeny by incorporating evolutionary thinking in all aspects of biology. A recent study by Grunspan and colleagues, for example, showed that teaching about the evidence for evolution increased students' understanding of evolution in a college biology course. For more information on how to teach about evolution, look up The Evolutionary Potential in 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 studying fossils, comparing species and studying living organisms. Evolution isn't a flims moment; it is an ongoing process that continues to be observed today. Bacteria evolve and resist antibiotics, viruses reinvent themselves and escape new drugs and animals change their behavior in response to a changing planet. The resulting changes are often evident.
It wasn't until late 1980s when biologists began to realize that natural selection was in action. The key to this is that different traits can confer a different rate of survival as well as reproduction, and may be passed down from one generation to the next.
In the past, when one particular allele - the genetic sequence that controls coloration - was present in a population of interbreeding organisms, it might rapidly become more common than the other alleles. Over time, that would mean the number of black moths in 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 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 one strain. 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 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 is hard for some to accept.
Another example of microevolution is that mosquito genes that are resistant to pesticides are more prevalent in populations where insecticides are used. This is due to pesticides causing an exclusive pressure that favors individuals who have resistant genotypes.
The rapidity of evolution has led to a growing appreciation of its importance especially in a planet that is largely shaped by human activity. This includes climate change, pollution, and habitat loss, which prevents many species from adapting. Understanding evolution will help us make better decisions about the future of our planet and the life of its inhabitants.
