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Are You Getting The Most Out You Evolution Site?
The Academy's Evolution Site

Biological evolution is a central concept in biology. The Academies have long been involved in helping people who are interested in science comprehend the concept of evolution and how it permeates all areas of scientific exploration.

This site provides a range of sources for teachers, students and general readers of evolution. It contains key video clips from NOVA and WGBH produced 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 symbolizing unity and love. It also has many practical uses, like providing a framework to understand the evolution of species and how they react to changing environmental conditions.

The first attempts at depicting the biological world focused on the classification of organisms into distinct categories which were distinguished by physical and metabolic characteristics1. These methods, which rely 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 a tree of life2. The trees are mostly composed of eukaryotes, while the diversity of bacterial species is greatly underrepresented3,4.

Genetic techniques have greatly expanded our ability to depict the Tree of Life by circumventing the requirement for direct observation and experimentation. In particular, molecular methods allow us to construct trees using sequenced markers, such as the small subunit ribosomal gene.

The Tree of Life has been significantly expanded by genome sequencing. However there is still a lot of diversity to be discovered. This is especially true for microorganisms that are difficult to cultivate, and are usually present in a single sample5. A recent analysis of all genomes resulted in an unfinished draft of the Tree of Life. This includes a variety of bacteria, archaea and other organisms that have not yet been isolated, or their diversity is not well understood6.


This expanded Tree of Life is particularly useful for assessing the biodiversity of an area, helping to determine if certain habitats require protection. This information can be used in a variety of ways, such as identifying new drugs, combating diseases and improving the quality of crops. This information is also extremely beneficial in conservation efforts. It can aid biologists in identifying areas that are likely to be home to cryptic species, which may have vital metabolic functions and be vulnerable to human-induced change. While funds to protect biodiversity are important, the best method to protect the world's biodiversity is to equip more people in developing countries with the necessary knowledge to act locally and promote conservation.

Phylogeny

A phylogeny is also known as an evolutionary tree, illustrates the relationships between different groups of organisms. Using molecular data similarities and differences in morphology, or ontogeny (the process of the development of an organism) scientists can construct a phylogenetic tree that illustrates the evolutionary relationships 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 ) determines the relationship between organisms that share similar traits that evolved from common ancestral. These shared traits could be either analogous or homologous. Homologous traits share their underlying evolutionary path, while analogous traits look like they do, but don't have the identical origins. Scientists group similar traits into a grouping referred to as a clade. All organisms in a group have a common characteristic, for example, amniotic egg production. They all came from an ancestor that had these eggs. A phylogenetic tree can be built by connecting the clades to identify the species that are most closely related to each other.

To create a more thorough and accurate phylogenetic tree, scientists make use of molecular data from DNA or RNA to determine the connections between organisms. This information is more precise than morphological data and gives evidence of the evolutionary background of an organism or group. Molecular data allows researchers to identify the number of species who share a common ancestor and to estimate their evolutionary age.

The phylogenetic relationship can be affected by a variety of factors, including phenotypicplasticity. This is a type behavior that changes due to particular environmental conditions. This can cause a trait to appear more like a species another, clouding the phylogenetic signal. This problem can be mitigated by using cladistics. This is a method that incorporates a combination of analogous and homologous features in the tree.

In addition, phylogenetics can aid in predicting the time and pace of speciation. This information can assist conservation biologists decide which species to protect from the threat of extinction. Ultimately, it is the preservation of phylogenetic diversity which will create an ecosystem that is complete and balanced.

Evolutionary Theory

The fundamental concept of evolution is that organisms acquire different features over time due to their interactions with their environments. Several theories of evolutionary change have been proposed by a wide range of scientists such as the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who proposed that a living organism develop gradually according to its needs, the Swedish botanist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical taxonomy, as well as Jean-Baptiste Lamarck (1744-1829) who suggested that the use or non-use of traits can cause changes that could be passed on to offspring.

In the 1930s and 1940s, ideas from a variety of fields--including genetics, natural selection, and particulate inheritance - came together to form the modern evolutionary theory synthesis which explains 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, called genetic drift or mutation, gene flow, and sexual selection, is a cornerstone of modern evolutionary biology and can be mathematically described.

Recent discoveries in the field of evolutionary developmental biology have shown that genetic variation can be introduced into a species by genetic drift, mutation, and reshuffling of genes during sexual reproduction, and also through migration between populations. These processes, along with other ones like directional selection and genetic erosion (changes in the frequency of the genotype over time) can lead to evolution which is defined by changes in the genome of the species over time, and also the change in phenotype over time (the expression of the genotype in the individual).

Incorporating evolutionary thinking into all aspects of biology education can improve student understanding of the concepts of phylogeny and evolution. In a study 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 on how to teach about evolution, please read The Evolutionary Potential in All Areas of Biology and Thinking Evolutionarily A Framework for Infusing Evolution in Life Sciences Education.

Evolution in Action

Traditionally, scientists have studied evolution through looking back, studying fossils, comparing species and observing living organisms. Evolution is not a past moment; it is an ongoing process that continues to be observed today. Bacteria mutate and resist antibiotics, viruses evolve and are able to evade new medications, and animals adapt their behavior to the changing environment. The results are often apparent.

However, it wasn't until late 1980s that biologists realized that natural selection could be seen in action, as well. The key is that various traits have different rates of survival and reproduction (differential fitness) and are passed down from one generation to the next.

In the past when one particular allele - the genetic sequence that defines color in a group of interbreeding organisms, it might quickly become more prevalent than other alleles. Over time, that would mean that the number of black moths in a population 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 particular species has a rapid turnover of its generation like bacteria. Since 1988 biologist Richard Lenski has been tracking twelve populations of E. coli that descended from a single strain; samples of each population are taken regularly and over 500.000 generations have been observed.

Lenski's work has shown that mutations can alter the rate of change and the efficiency at which a population reproduces. 에볼루션 바카라 사이트 shows evolution takes time, a fact that is difficult for some to accept.

Microevolution can be observed in the fact that mosquito genes for pesticide resistance are more prevalent in populations where insecticides have been used. Pesticides create an exclusive pressure that favors those who have resistant genotypes.

The rapidity of evolution has led to a growing recognition of its importance especially in a planet that is largely shaped by human activity. 에볼루션 바카라 사이트 includes climate change, pollution, and habitat loss, which prevents many species from adapting. Understanding the evolution process will assist you in making better choices regarding the future of the planet and its inhabitants.