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The Academy's Evolution Site

Biological evolution is one of the most fundamental concepts in biology. The Academies are committed to helping those who are interested in science to comprehend the evolution theory and how it is permeated across all areas of scientific research.

This site provides students, teachers and general readers with a wide range of learning resources about evolution. It has important video clips from NOVA and WGBH's science programs on DVD.

Tree of Life

The Tree of Life is an ancient symbol that represents the interconnectedness of life. It appears in many cultures and spiritual beliefs as an emblem of unity and love. It can be used in many practical ways as well, including providing a framework for understanding the history of species and how they react to changes in environmental conditions.

Early approaches to depicting the biological world focused on categorizing species into distinct categories that had been distinguished by physical and metabolic characteristics1. These methods, which rely on sampling of different parts of living organisms or small fragments of their DNA, significantly expanded the diversity that could be included in a tree of life2. These trees are largely composed by eukaryotes and bacterial diversity is vastly underrepresented3,4.

Genetic techniques have significantly expanded our ability to visualize the Tree of Life by circumventing the need for direct observation and experimentation. In particular, molecular methods enable us to create trees by using sequenced markers like the small subunit ribosomal gene.

Despite the rapid growth of the Tree of Life through genome sequencing, a lot of biodiversity is waiting to be discovered. This is particularly true of microorganisms, which can be difficult to cultivate and are typically only represented in a single sample5. A recent study of all genomes known to date has produced a rough draft of the Tree of Life, including many bacteria and archaea that have not been isolated, and which are not well understood.

This expanded Tree of Life is particularly useful in assessing the diversity of an area, assisting to determine if specific habitats require protection. The information can be used in a range of ways, from identifying the most effective treatments to fight disease to enhancing crop yields. This information is also valuable to conservation efforts. It can help biologists identify areas that are most likely to have cryptic species, which may have important metabolic functions and be vulnerable to the effects of human activity. While funds to protect biodiversity are crucial but the most effective way to protect the world's biodiversity is for more people in developing countries to be equipped with the knowledge to act locally to promote conservation from within.

Phylogeny

A phylogeny (also known as an evolutionary tree) shows the relationships between species. By using molecular information as well as morphological similarities and distinctions or ontogeny (the course of development of an organism) scientists can create a phylogenetic tree which illustrates the evolution of taxonomic categories. The phylogeny of a tree plays an important role in understanding biodiversity, genetics and evolution.

A basic phylogenetic Tree (see Figure PageIndex 10 Determines the relationship between organisms with similar traits and evolved from a common ancestor. These shared traits are either analogous or homologous. Homologous traits are similar in their evolutionary path. Analogous traits may look similar, but they do not have the same origins. Scientists combine similar traits into a grouping referred to as a Clade. For instance, all of the organisms that make up a clade share the trait of having amniotic eggs and evolved from a common ancestor which had eggs. The clades are then linked to form a phylogenetic branch that can determine which organisms have the closest relationship to.

For a more precise and accurate phylogenetic tree scientists use molecular data from DNA or RNA to determine the connections between organisms. This data is more precise than the morphological data and provides evidence of the evolution history of an individual or group. The analysis of molecular data can help researchers identify the number of species who share an ancestor common to them and estimate their evolutionary age.

The phylogenetic relationships of a species can be affected by a variety of factors, including phenotypicplasticity. This is a type behavior that alters as a result of particular environmental conditions. This can cause a characteristic to appear more similar to one species than another, clouding the phylogenetic signal. However, this problem can be cured by the use of techniques like cladistics, which combine similar and homologous traits into the tree.

In addition, phylogenetics helps determine the duration and speed at which speciation takes place. This information will assist conservation biologists in making decisions about which species to protect from disappearance. Ultimately, it is the preservation of phylogenetic diversity that will lead to an ecosystem that is complete and balanced.

Evolutionary Theory

The central theme in evolution is that organisms alter over time because of their interactions with their environment. Many theories of evolution 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 according to its needs as well as 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 cause changes that can be passed onto offspring.

In the 1930s and 1940s, concepts from various areas, including genetics, 에볼루션 블랙잭 natural selection, and particulate inheritance, were brought together to form a contemporary synthesis of evolution theory. This describes how evolution is triggered by the variations in genes within a population and 에볼루션 바카라 how these variants change with time due to natural selection. This model, called genetic drift mutation, gene flow, and sexual selection, is a cornerstone of the current evolutionary biology and is mathematically described.

Recent discoveries in the field of evolutionary developmental biology have revealed how variations can be introduced to a species through genetic drift, mutations and reshuffling of genes during sexual reproduction, and even migration between populations. These processes, along with others, such as directional selection and gene erosion (changes in frequency of genotypes over time) can result in evolution. Evolution is defined by changes in the genome over time as well as changes in the phenotype (the expression of genotypes within individuals).

Incorporating evolutionary thinking into all aspects of biology education can increase student understanding of the concepts of phylogeny and evolution. In a recent study conducted by Grunspan and co., it was shown that teaching students about the evidence for evolution boosted their understanding of evolution in a college-level course in biology. For more information about how to teach evolution, see The Evolutionary Potential in All Areas of Biology or Thinking Evolutionarily A Framework for Integrating Evolution into Life Sciences Education.

Evolution in Action

Scientists have traditionally studied evolution by looking in the past, 에볼루션 바카라 사이트코리아 (discover this) studying fossils, and comparing species. They also observe living organisms. But evolution isn't just something that occurred in the past. It's an ongoing process, taking place right now. The virus reinvents itself to avoid new drugs and bacteria evolve to resist antibiotics. Animals adapt their behavior in the wake of a changing environment. The resulting changes are often visible.

It wasn't until the 1980s that biologists began realize that natural selection was in action. The key is that various traits have different rates of survival and reproduction (differential fitness) and can be transferred 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 could quickly become more common than the other alleles. In time, this could mean that the number of moths that have black pigmentation could increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.

The ability to observe evolutionary change is easier when a species has a rapid generation turnover like bacteria. Since 1988, Richard Lenski, a biologist, has tracked twelve populations of E.coli that descend from one strain. Samples of each population have been taken regularly and 에볼루션사이트 more than 500.000 generations of E.coli have been observed to have passed.

Lenski's research has shown that a mutation can profoundly alter the speed at which a population reproduces and, consequently, the rate at which it alters. It also proves that evolution takes time, a fact that some find difficult to accept.

Microevolution is also evident in the fact that mosquito genes that confer resistance to pesticides are more prevalent in areas that have used insecticides. This is due to the fact that the use of pesticides creates a pressure that favors individuals with resistant genotypes.

The rapid pace at which evolution takes place has led to a growing appreciation of its importance in a world shaped by human activity--including climate changes, pollution and the loss of habitats that prevent many species from adjusting. Understanding evolution will assist you in making better choices regarding the future of the planet and its inhabitants.