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The Academy's Evolution Site

Biological evolution is a central concept in biology. The Academies are committed to helping those who are interested in science learn about the theory of evolution and how it is permeated in all areas of scientific research.

This site provides a range of resources for teachers, students and general readers of evolution. It includes key video clip 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. It appears in many spiritual traditions and cultures as symbolizing unity and love. It has many practical applications as well, such as 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 separating species into distinct categories that had been identified by their physical and metabolic characteristics1. 에볼루션 바카라 , which relied on sampling of different parts of living organisms or sequences of short fragments of their DNA greatly increased the variety of organisms that could be represented in the tree of life2. However the trees are mostly made up of eukaryotes. Bacterial diversity remains vastly underrepresented3,4.

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

Despite the dramatic expansion of the Tree of Life through genome sequencing, a large amount of biodiversity awaits discovery. This is particularly true for microorganisms that are difficult to cultivate, and which are usually only found in a single specimen5. A recent study of all genomes known to date has produced a rough draft of the Tree of Life, including a large number of bacteria and archaea that have not been isolated and their diversity is not fully understood6.

The expanded Tree of Life is particularly useful in assessing the diversity of an area, which can help to determine whether specific habitats require special protection. This information can be used in a variety of ways, from identifying the most effective medicines to combating disease to enhancing crops. The information is also useful to conservation efforts. It can aid biologists in identifying those areas that are most likely contain cryptic species with potentially important metabolic functions that could be vulnerable to anthropogenic change. While funds to protect biodiversity are essential, the best method to preserve the world's biodiversity is to empower the people of developing nations with the knowledge they need to act locally and support conservation.

Phylogeny

A phylogeny, also called an evolutionary tree, illustrates the connections between various groups of organisms. By using molecular information as well as morphological similarities and distinctions or ontogeny (the process of the development of an organism) scientists can construct a phylogenetic tree that illustrates 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 Identifies the relationships between organisms with similar characteristics and have evolved from an ancestor with common traits. These shared traits can be either homologous or analogous. Homologous traits are similar in their evolutionary roots while analogous traits appear similar but do not have the same ancestors. Scientists organize similar traits into a grouping referred to as a the clade. All members of a clade have a common characteristic, like amniotic egg production. They all came from an ancestor who had these eggs. A phylogenetic tree is then built by connecting the clades to identify the organisms who are the closest to one another.

For a more detailed and accurate phylogenetic tree scientists rely on molecular information from DNA or RNA to identify the relationships among organisms. This information is more precise and gives evidence of the evolution of an organism. Molecular data allows researchers to identify the number of species who share the same ancestor and estimate their evolutionary age.

The phylogenetic relationships between species can be affected by a variety of factors, including phenotypic plasticity a type of behavior that alters in response to unique environmental conditions. This can cause a characteristic to appear more like a species another, clouding the phylogenetic signal. This issue can be cured by using cladistics. This is a method that incorporates a combination of homologous and analogous traits in the tree.

In addition, phylogenetics helps determine the duration and speed at which speciation takes place. This information can assist conservation biologists in making decisions about which species to protect from extinction. It is ultimately the preservation of phylogenetic diversity that will result in a complete and balanced ecosystem.

Evolutionary Theory

The central theme of evolution is that organisms develop distinct characteristics over time due to their interactions with their environments. Many scientists have come up with theories of evolution, including the Islamic naturalist Nasir al-Din al-Tusi (1201-274), who believed that a living thing would evolve according to its own needs as well as the Swedish taxonomist Carolus Linnaeus (1707-1778), who created the modern taxonomy system that is hierarchical and Jean-Baptiste Lamarck (1844-1829), who believed that the use or non-use of traits can cause changes that are passed on to the

In the 1930s and 1940s, concepts from various fields, including natural selection, genetics & particulate inheritance, merged to form a modern synthesis of evolution theory. This explains how evolution happens through the variation in genes within a population and how these variations change with time due to natural selection. This model, which includes genetic drift, mutations as well as gene flow and sexual selection, can be mathematically described mathematically.

Recent developments in the field of evolutionary developmental biology have revealed that variations can be introduced into a species by mutation, genetic drift, and reshuffling genes during sexual reproduction, as well as by migration between populations. 에볼루션게이밍 , as well as others like directional selection and genetic erosion (changes in the frequency of a genotype over time) can lead to 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 in the individual).

Incorporating evolutionary thinking into all aspects of biology education can improve students' understanding of phylogeny and evolution. A recent study by Grunspan and colleagues, for example demonstrated that teaching about the evidence that supports evolution increased students' acceptance of evolution in a college-level biology course. To find out more about how to teach about evolution, please look up The Evolutionary Potential of 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. But evolution isn't just something that occurred in the past; it's an ongoing process that is happening today. Bacteria transform and resist antibiotics, viruses re-invent themselves and elude new medications and animals change their behavior to the changing environment. The resulting changes are often visible.

It wasn't until late 1980s that biologists began to realize that natural selection was at work. The key to this is that different traits can confer the ability to survive at different rates and reproduction, and they can be passed on from generation to generation.

In the past, if a certain allele - the genetic sequence that determines color - was present in a population of organisms that interbred, it could become more common than other allele. As time passes, this could mean that the number of moths sporting black pigmentation in a population may 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, as with bacteria. Since 1988, biologist Richard Lenski has been tracking twelve populations of E. bacteria that descend from a single strain; samples from each population are taken regularly, and over 50,000 generations have now been observed.


Lenski's research has shown that a mutation can profoundly alter the speed at the rate at which a population reproduces, and consequently, the rate at which it alters. It also shows that evolution takes time, something that is hard for some to accept.

Microevolution can also be seen in the fact that mosquito genes for resistance to pesticides are more prevalent in areas where insecticides have been used. This is because the use of pesticides creates a selective pressure that favors those with resistant genotypes.

The rapidity of evolution has led to a greater awareness of its significance particularly in a world that is largely shaped by human activity. This includes pollution, climate change, and habitat loss that prevents many species from adapting. Understanding evolution can help us make better choices about the future of our planet, and the life of its inhabitants.