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The Academy's Evolution Site

Biological evolution is one of the most important concepts in biology. The Academies have been active for a long time in helping those interested in science comprehend the theory of evolution and how it affects every area of scientific inquiry.

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

Tree of Life

The Tree of Life, an ancient symbol, represents the interconnectedness of all life. It is an emblem of love and unity in many cultures. It has numerous practical applications as well, such as providing a framework to understand the history of species, and how they respond to changing environmental conditions.

Early attempts to describe the biological world were founded on categorizing organisms on their metabolic and physical characteristics. These methods, which are based on the collection of various parts of organisms or short DNA fragments have significantly increased the diversity of a Tree of Life2. However, these trees are largely composed of eukaryotes; bacterial diversity remains vastly underrepresented3,4.

Genetic techniques have greatly broadened our ability to represent the Tree of Life by circumventing the requirement for direct observation and experimentation. Particularly, molecular methods enable us to create trees using sequenced markers, such as the small subunit of ribosomal RNA gene.

Despite the massive expansion of the Tree of Life through genome sequencing, a large amount of biodiversity remains to be discovered. This is particularly relevant to microorganisms that are difficult to cultivate and which are usually only found in a single specimen5. A recent analysis of all known genomes has produced a rough draft version of the Tree of Life, including many bacteria and archaea that have not been isolated, 에볼루션 사이트 룰렛, willard-Wooten-2.mdwrite.net, and which are not well understood.

This expanded Tree of Life is particularly useful for assessing the biodiversity of an area, helping to determine if specific habitats require special protection. The information is useful in many ways, including finding new drugs, battling diseases and enhancing crops. This information is also extremely valuable for conservation efforts. It can help biologists identify those areas that are most likely contain cryptic species with potentially important metabolic functions that may be at risk of anthropogenic changes. Although funding to protect biodiversity are crucial however, the most effective method to protect the world's biodiversity is for more people living in developing countries to be empowered with the necessary knowledge to take action locally to encourage conservation from within.

Phylogeny

A phylogeny, also called an evolutionary tree, illustrates the relationships between groups of organisms. Using molecular data similarities and differences in morphology, or ontogeny (the process of the development of an organism), scientists can build an phylogenetic tree that demonstrates the evolution of taxonomic categories. The role of phylogeny is crucial in understanding genetics, biodiversity and evolution.

A basic phylogenetic Tree (see Figure PageIndex 10 ) determines the relationship between organisms that share similar traits that have evolved from common ancestral. These shared traits can be homologous, or analogous. Homologous characteristics are identical in their evolutionary paths. Analogous traits could appear like they are, but they do not have the same origins. Scientists group similar traits into a grouping known as a the clade. For instance, all of the organisms that make up a clade have the characteristic of having amniotic eggs. They evolved from a common ancestor that had eggs. A phylogenetic tree is then constructed by connecting clades to determine the organisms who are the closest to one another.

For a more detailed and precise phylogenetic tree scientists use molecular data from DNA or RNA to determine the relationships among organisms. This data is more precise than morphological information and gives evidence of the evolutionary background of an organism or group. Researchers can utilize Molecular Data to calculate the age of evolution of organisms and identify how many species have a common ancestor.

The phylogenetic relationships between organisms can be affected by a variety of factors, including phenotypic flexibility, an aspect of behavior 에볼루션 룰렛 (Suggested Resource site) that changes in response to unique environmental conditions. This can make a trait appear more similar to a species than to the other, obscuring the phylogenetic signals. However, this problem can be solved through the use of techniques such as cladistics that incorporate a combination of analogous and homologous features into the tree.

Additionally, phylogenetics can help determine the duration and rate at which speciation occurs. This information can assist conservation biologists make decisions about which species to protect from extinction. In the end, it's the preservation of phylogenetic diversity that will result in a complete and balanced ecosystem.

Evolutionary Theory

The central theme of evolution is that organisms acquire different features over time based on their interactions with their environment. A variety of theories about evolution have been developed by a wide range 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 designed 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 can be passed on to the offspring.

In the 1930s and 1940s, ideas from a variety of fields -- including genetics, natural selection, and particulate inheritance -- came together to create the modern evolutionary theory, which defines how evolution occurs through the variations of genes within a population and how these variants change over time as a result of natural selection. This model, which is known as genetic drift mutation, gene flow, and sexual selection, is a cornerstone of modern evolutionary biology and can be mathematically explained.

Recent developments in the field of evolutionary developmental biology have revealed how variations can be introduced to a species via mutations, genetic drift, reshuffling genes during sexual reproduction and the movement between populations. These processes, as well as others like directional selection and genetic erosion (changes in the frequency of an individual's genotype over time) can result in evolution, which is defined by changes in the genome of the species over time and also by changes in phenotype as time passes (the expression of the genotype within the individual).

Incorporating evolutionary thinking into all aspects of biology education can increase students' understanding of phylogeny as well as evolution. In a recent study conducted by Grunspan and co., it was shown that teaching students about the evidence for evolution increased their understanding of evolution in the course of a college biology. For more details on how to teach evolution look up 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 studied evolution through looking back in the past, analyzing fossils and comparing species. They also study living organisms. But evolution isn't a thing that occurred in the past; it's an ongoing process that is that is taking place right now. Bacteria transform and resist antibiotics, viruses re-invent themselves and are able to evade new medications and animals change their behavior 에볼루션 사이트 in response to the changing environment. The changes that result are often evident.

It wasn't until late-1980s that biologists realized that natural selection can be observed in action as well. The key is that different characteristics result in different rates of survival and reproduction (differential fitness), and can be passed from one generation to the next.

In the past, when one particular allele--the genetic sequence that determines coloration--appeared in a population of interbreeding species, it could rapidly become more common than other alleles. In time, this could mean that the number of moths sporting black pigmentation in a group 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 evolution when the species, like bacteria, has a high generation turnover. Since 1988, Richard Lenski, a biologist, has been tracking twelve populations of E.coli that are descended from a single strain. Samples of each population have been collected regularly 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 demonstrates that evolution takes time, which is difficult for some to accept.

Microevolution can also be seen in the fact that mosquito genes for pesticide resistance are more common in populations where insecticides have been used. That's because the use of pesticides creates a pressure that favors people who have resistant genotypes.

The speed of evolution taking place has led to an increasing awareness of its significance in a world shaped by human activity--including climate changes, pollution and the loss of habitats that prevent many species from adjusting. Understanding the evolution process can aid you in making better decisions regarding the future of the planet and its inhabitants.