The Academy's Evolution Site
The concept of biological evolution is among the most central concepts in biology. The Academies are involved in helping those who are interested in science understand evolution theory and how it is incorporated across all areas of scientific research.
This site provides teachers, students and general readers with a variety of learning resources about evolution. It includes key video clips from NOVA and WGBH's science programs on DVD.
Tree of Life
The Tree of Life, an ancient symbol, symbolizes the interconnectedness of all life. It is an emblem of love and unity across many cultures. It also has many practical applications, such as providing a framework to understand the evolution of species and how they respond to changes in the environment.
Early attempts to represent the biological world were built on categorizing organisms based on their physical and metabolic characteristics. These methods, which rely on sampling of different parts of living organisms or on sequences of short DNA fragments, significantly increased the variety that could be represented in a tree of life2. These trees are largely composed of eukaryotes, while the diversity of bacterial species is greatly underrepresented3,4.
Genetic techniques have greatly broadened our ability to visualize the Tree of Life by circumventing the need for direct observation and experimentation. We can create trees using molecular techniques like the small-subunit ribosomal gene.
Despite the rapid growth of the Tree of Life through genome sequencing, much biodiversity still remains to be discovered. This is particularly true for microorganisms that are difficult to cultivate and are usually 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 archaea and bacteria that are not isolated and which are not well understood.
This expanded Tree of Life can be used to evaluate the biodiversity of a particular area and determine if certain habitats require special protection. This information can be used in a range of ways, from identifying the most effective medicines to combating disease to enhancing the quality of crops. The information is also incredibly beneficial in conservation efforts. It helps biologists discover areas that are most likely to have cryptic species, which could perform important metabolic functions, and could be susceptible to changes caused by humans. Although funding to protect biodiversity are essential but the most effective way to ensure the preservation of biodiversity around the world is for more people living in developing countries to be empowered with the necessary knowledge to act locally in order to promote conservation from within.
Phylogeny
A phylogeny (also known as an evolutionary tree) shows the relationships between organisms. By using molecular information as well as morphological similarities and distinctions or ontogeny (the process of the development of an organism) scientists can create a phylogenetic tree that illustrates the evolutionary relationships between taxonomic categories. The role of phylogeny is crucial in understanding biodiversity, genetics 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 are either homologous or analogous. Homologous traits share their underlying evolutionary path while analogous traits appear similar but do not have the same ancestors. Scientists group similar traits together into a grouping known as a the clade. For example, all of the organisms that make up a clade share the characteristic of having amniotic eggs. They evolved from a common ancestor which had these eggs. A phylogenetic tree is constructed by connecting the clades to identify the species that are most closely related to one another.
Scientists use molecular DNA or RNA data to create a phylogenetic chart that is more accurate and precise. This information is more precise and gives evidence of the evolutionary history of an organism. The analysis of molecular data can help researchers identify the number of species that 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 the phenomenon of phenotypicplasticity. 에볼루션 슬롯 is a kind of behavior that changes as a result of unique environmental conditions. This can cause a particular trait to appear more similar in one species than other species, which can obscure the phylogenetic signal. This problem can be addressed by using cladistics. This is a method that incorporates an amalgamation of analogous and homologous features in the tree.
Additionally, phylogenetics can help predict the duration and rate of speciation. This information will assist conservation biologists in making choices about which species to safeguard from disappearance. In the end, it's the conservation of phylogenetic diversity which will create an ecosystem that is complete and balanced.
Evolutionary Theory
The fundamental concept of evolution is that organisms develop distinct characteristics over time as a result of their interactions with their surroundings. Several theories of evolutionary change have been developed by a wide variety of scientists including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who proposed that a living organism develop slowly according to its needs as well as 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 causes changes that could be passed on to the offspring.
In the 1930s & 1940s, ideas from different fields, such as genetics, natural selection, and particulate inheritance, were brought together to form a contemporary evolutionary theory. This defines how evolution happens through the variations in genes within a population and how these variants alter over time due to natural selection. This model, known as genetic drift mutation, gene flow, and sexual selection, is a key element of modern evolutionary biology and can be mathematically explained.
Recent discoveries in evolutionary developmental biology have demonstrated how variations can be introduced to a species by mutations, genetic drift, reshuffling genes during sexual reproduction and the movement between populations. These processes, along with others, such as the directional selection process and the erosion of genes (changes to the frequency of genotypes over time) can lead to evolution. Evolution is defined by changes in the genome over time as well as changes in the phenotype (the expression of genotypes in an individual).
Incorporating evolutionary thinking into all areas 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 a college-level course in biology. For more details about how to teach evolution, see The Evolutionary Potency in all Areas of Biology or Thinking Evolutionarily: a Framework for Infusing Evolution into Life Sciences Education.
Evolution in Action
Traditionally scientists have studied evolution by looking back, studying fossils, comparing species and studying living organisms. But evolution isn't just something that happened in the past. It's an ongoing process, that is taking place in the present. Viruses reinvent themselves to avoid new drugs and bacteria evolve to resist antibiotics. Animals alter their behavior as a result of a changing environment. The results are usually evident.
It wasn't until late 1980s that biologists realized that natural selection can be observed in action as well. The key is the fact that different traits result in a different rate of survival and reproduction, and they can be passed down from one generation to the next.
In the past, if an allele - the genetic sequence that determines colour - was present in a population of organisms that interbred, it could be more prevalent than any other allele. As time passes, that could mean that the number of black moths within the population 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 rapid generation turnover. Since 1988 the biologist Richard Lenski has been tracking twelve populations of E. bacteria that descend from a single strain; samples of each are taken every day and more than 50,000 generations have now passed.
Lenski's research has shown that a mutation can profoundly alter the rate at which a population reproduces--and so, the rate at which it alters. 에볼루션 바카라 체험 shows that evolution takes time, a fact that is difficult for some to accept.
Another example of microevolution is how mosquito genes for resistance to pesticides appear more frequently in populations where insecticides are employed. This is because the use of pesticides causes a selective pressure that favors those who have resistant genotypes.
The rapidity of evolution has led to a growing appreciation of its importance, especially in a world which is largely shaped by human activities. This includes the effects of climate change, pollution and habitat loss that hinders many species from adapting. Understanding evolution will assist you in making better choices about the future of the planet and its inhabitants.