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The Academy's Evolution Site

The concept of biological evolution is a fundamental concept in biology. The Academies are committed to helping those interested in science learn about the theory of evolution and how it is permeated throughout all fields of scientific research.

This site offers a variety of resources for students, 에볼루션 바카라사이트 teachers 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 symbolizes the interconnectedness of all life. It is a symbol of love and unity in many cultures. It can be used in many practical ways in addition to providing a framework for understanding the history of species, and how they respond to changing environmental conditions.

Early attempts to represent the biological world were founded on categorizing organisms on their physical and metabolic characteristics. These methods, based on sampling of different parts of living organisms, or short DNA fragments, greatly increased the variety of organisms that could be represented in the tree of life2. However, these trees are largely composed of eukaryotes; bacterial diversity remains vastly underrepresented3,4.

By avoiding the need for direct observation and experimentation genetic techniques have allowed us to depict the Tree of Life in a more precise manner. Particularly, molecular techniques enable us to create trees using sequenced markers like the small subunit ribosomal RNA gene.

The Tree of Life has been greatly expanded thanks to genome sequencing. However, there is still much biodiversity to be discovered. This is particularly true for microorganisms that are difficult to cultivate, and which are usually only found in a single specimen5. A recent analysis of all genomes that are known has created a rough draft of the Tree of Life, including many bacteria and archaea that have not been isolated, and their diversity is not fully understood6.

This expanded Tree of Life is particularly beneficial in assessing the biodiversity of an area, assisting to determine if specific habitats require special protection. This information can be used in many ways, including finding new drugs, battling diseases and enhancing crops. It is also useful to conservation efforts. It can aid biologists in identifying the areas that are most likely to contain cryptic species that could have significant metabolic functions that could be at risk from anthropogenic change. While funds to protect biodiversity are crucial, ultimately the best way to protect the world's biodiversity is for more people in developing countries to be empowered with the knowledge to take action locally to encourage conservation from within.

Phylogeny

A phylogeny (also called an evolutionary tree) shows the relationships between different organisms. Using molecular data similarities and differences in morphology, or ontogeny (the process of the development of an organism) scientists can construct an phylogenetic tree that demonstrates the evolutionary relationship between taxonomic groups. Phylogeny plays a crucial role in understanding the relationship between genetics, biodiversity and evolution.

A basic phylogenetic Tree (see Figure PageIndex 10 ) is a method of identifying the relationships between organisms with similar traits that have evolved from common ancestors. These shared traits may be homologous, or analogous. Homologous traits share their evolutionary origins, while analogous traits look similar, but do not share the same ancestors. Scientists group similar traits together into a grouping referred to as a clade. All organisms in a group share a characteristic, like amniotic egg production. They all evolved from an ancestor that had these eggs. The clades then join to create a phylogenetic tree to determine which organisms have the closest relationship.

Scientists utilize DNA or RNA molecular information to construct a phylogenetic graph that is more accurate and detailed. This information is more precise than the morphological data and provides evidence of the evolutionary history of an organism or group. The analysis of molecular data can help researchers identify the number of organisms that have an ancestor common to them and 에볼루션 estimate their evolutionary age.

The phylogenetic relationships of a species can be affected by a variety of factors such as the phenomenon of phenotypicplasticity. This is a kind of behavior that changes due to specific environmental conditions. This can make a trait appear more similar to a species than another which can obscure the phylogenetic signal. However, this issue can be solved through the use of methods like cladistics, which incorporate a combination of homologous and analogous features into the tree.

In addition, phylogenetics helps determine the duration and rate of speciation. This information can assist conservation biologists in making decisions about which species to save from disappearance. In the end, it is the preservation of phylogenetic diversity that will result in an ecosystem that is complete and balanced.

Evolutionary Theory

The fundamental concept of evolution is that organisms acquire distinct characteristics over time as a result of their interactions with their environment. Many scientists have developed theories of evolution, such as the Islamic naturalist Nasir al-Din al-Tusi (1201-274), who believed that an organism could evolve according to its individual requirements and needs, the Swedish taxonomist Carolus Linnaeus (1707-1778), who created the modern taxonomy system that is hierarchical and Jean-Baptiste Lamarck (1844-1829), who suggested that the use or non-use of certain traits can result in changes that can be passed on to future generations.

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 synthesis that explains how evolution happens through the variation of genes within a population and how these variants change in time due to natural selection. This model, known as genetic drift or mutation, gene flow and sexual selection, is a key element of current evolutionary biology, and 에볼루션 무료체험 is mathematically described.

Recent discoveries in the field of evolutionary developmental biology have demonstrated how variation can be introduced to a species via mutations, genetic drift or reshuffling of genes in sexual reproduction and migration between populations. These processes, as well as others like directional selection and genetic erosion (changes in the frequency of the genotype over time) can result in evolution which is defined by change in the genome of the species over time, and the change in phenotype as time passes (the expression of the genotype within the individual).

Students can better understand the concept of phylogeny by using evolutionary thinking in all aspects of biology. A recent study by Grunspan and colleagues, for instance, showed that teaching about the evidence that supports evolution increased students' understanding of evolution in a college biology course. For more information on how to teach about evolution read The Evolutionary Potency in all Areas of Biology or Thinking Evolutionarily as a Framework for Infusing 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 distant event, but an ongoing process. Bacteria mutate and resist antibiotics, viruses reinvent themselves and are able to evade new medications and animals change their behavior 에볼루션 in response to the changing environment. The changes that result are often apparent.

It wasn't until the 1980s that biologists began realize that natural selection was in play. The key is that various traits confer 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 defines color in a population of interbreeding organisms, it might quickly become more common than other alleles. In time, this could mean that the number of moths sporting black pigmentation could increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.

It is easier to observe evolutionary change when a species, such as bacteria, has a rapid 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 were taken frequently and more than 500.000 generations of E.coli have passed.

Lenski's research has revealed that a mutation can dramatically alter the efficiency with the rate at which a population reproduces, and consequently, 에볼루션 바카라 무료체험 the rate at which it alters. It also demonstrates that evolution takes time--a fact that some are unable to accept.

Another example of microevolution is how mosquito genes for 에볼루션 resistance to pesticides are more prevalent in populations where insecticides are employed. That's because the use of pesticides creates a selective pressure that favors individuals with resistant genotypes.

The speed at which evolution can take place has led to an increasing appreciation of its importance in a world that is shaped by human activities, including climate change, pollution, and the loss of habitats that prevent the species from adapting. Understanding evolution can help us make smarter decisions regarding the future of our planet, and the life of its inhabitants.