The Academy's Evolution Site
The concept of biological evolution is among the most important concepts in biology. The Academies are involved in helping those who are interested in science to learn about the theory of evolution and how it is incorporated in all areas of scientific research.
This site provides a wide range of sources for teachers, students, and general readers on evolution. It contains key video clips from NOVA and WGBH produced science programs on DVD.
Tree of Life
The Tree of Life, an ancient symbol, symbolizes the interconnectedness of all life. It appears in many cultures and spiritual beliefs as an emblem of unity and love. It can be used in many practical ways in addition to providing a framework to understand the history of species and how they react to changes in environmental conditions.
The first attempts to depict the world of biology were founded on categorizing organisms on their physical and metabolic characteristics. These methods are based on the collection of various parts of organisms or short DNA fragments, have significantly increased the diversity of a Tree of Life2. These trees are largely composed by eukaryotes and bacterial diversity is vastly underrepresented3,4.
Genetic techniques have greatly broadened our ability to depict the Tree of Life by circumventing the need for direct observation and experimentation. In particular, molecular methods enable us to create trees using sequenced markers, such as the small subunit ribosomal gene.
Despite the massive expansion of the Tree of Life through genome sequencing, much biodiversity still awaits discovery. This is particularly true of microorganisms that are difficult to cultivate and are often only present in a single sample5. A recent analysis of all genomes produced an initial draft of a Tree of Life. This includes a variety of bacteria, archaea and other organisms that have not yet been identified or the diversity of which is not fully understood6.
The expanded Tree of Life is particularly beneficial in assessing the biodiversity of an area, assisting to determine if specific habitats require protection. This information can be used in a variety of ways, including finding new drugs, fighting diseases and improving the quality of crops. It is also valuable for conservation efforts. It can aid biologists in identifying the areas most likely to contain cryptic species with potentially significant metabolic functions that could be vulnerable to anthropogenic change. Although funding to safeguard biodiversity are vital, ultimately the best 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 take action locally to encourage conservation from within.
Phylogeny
A phylogeny (also known as an evolutionary tree) depicts the relationships between species. Using molecular data as well as morphological similarities and distinctions, or ontogeny (the course of development of an organism) scientists can create an phylogenetic tree that demonstrates the evolution of taxonomic categories. Phylogeny is crucial in understanding biodiversity, evolution and genetics.
A basic phylogenetic tree (see Figure PageIndex 10 Identifies the relationships between organisms that have similar characteristics and have evolved from a common ancestor. These shared traits may be analogous, or homologous. Homologous traits are the same in terms of their evolutionary paths. Analogous traits could appear similar however they do not have the same origins. Scientists group similar traits together into a grouping known as a clade. Every organism in a group share a trait, such as amniotic egg production. They all evolved from an ancestor with these eggs. A phylogenetic tree can be constructed by connecting clades to identify the species who are the closest to each other.
To create a more thorough and accurate phylogenetic tree, scientists use molecular data from DNA or RNA to determine the connections between organisms. This information is more precise and provides evidence of the evolution history of an organism. Researchers can use Molecular Data to calculate the evolutionary age of organisms and identify how many species have a common ancestor.
The phylogenetic relationships of organisms can be influenced by several factors, including phenotypic flexibility, a type of behavior that alters in response to unique environmental conditions. This can cause a trait to appear more like a species other species, which can obscure the phylogenetic signal. However, this problem can be solved through the use of methods like cladistics, which combine similar and homologous traits into the tree.
In addition, phylogenetics helps determine the duration and speed of speciation. This information can help conservation biologists make decisions about which species to protect from extinction. It is ultimately the preservation of phylogenetic diversity which will result in an ecologically balanced and complete ecosystem.
Evolutionary Theory
The central theme of evolution is that organisms acquire various characteristics over time due to their interactions with their surroundings. A variety of theories about evolution 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 gradually according to its requirements and needs, the Swedish botanist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical taxonomy Jean-Baptiste Lamarck (1744-1829) who suggested that use or disuse of traits cause changes that can be passed onto offspring.
In the 1930s and 1940s, concepts from various fields, including natural selection, genetics & particulate inheritance, were brought together to form a modern evolutionary theory. This describes how evolution occurs by the variations in genes within the population, and how these variations alter over time due to natural selection. This model, called genetic drift, mutation, gene flow, and sexual selection, is the foundation of the current evolutionary biology and is mathematically described.
Recent discoveries in evolutionary developmental biology have shown how variations can be introduced to a species via mutations, genetic drift, reshuffling genes during sexual reproduction and the movement between populations. These processes, along with other ones like 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 within individuals).
Incorporating evolutionary thinking into all areas of biology education can increase student understanding of the concepts of phylogeny and evolutionary. In a recent study by Grunspan and co. It was found that teaching students about the evidence for evolution increased their acceptance of evolution during a college-level course in biology. For more information on 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
Scientists have traditionally studied evolution by looking in the past, analyzing fossils and comparing species. They also observe living organisms. Evolution is not a past event; it is a process that continues today. Bacteria transform and resist antibiotics, viruses re-invent themselves and elude new medications and animals alter their behavior to the changing climate. The changes that occur are often visible.
It wasn't until late 1980s that biologists began to realize that natural selection was also in play. The reason is that different traits have different rates of survival and reproduction (differential fitness), and can be transferred from one generation to the next.
In the past, if a certain allele - the genetic sequence that determines colour - appeared in a population of organisms that interbred, it could become more prevalent than any other allele. As time passes, that could mean that the number of black moths within a population could increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
Observing evolutionary change in action is easier when a particular species has a rapid turnover of its generation, as with bacteria. Since 1988, Richard Lenski, a biologist, has been tracking twelve populations of E.coli that are descended from a single strain. Samples from each population were taken regularly and more than 50,000 generations of E.coli have been observed to have passed.
에볼루션 슬롯게임 has shown that a mutation can dramatically alter the speed at which a population reproduces--and so the rate at which it changes. It also shows that evolution takes time, something that is difficult for some to accept.
Microevolution can also be seen in the fact that mosquito genes for resistance to pesticides are more prevalent in areas that have used insecticides. This is due to pesticides causing a selective pressure which favors those with resistant genotypes.
The rapidity of evolution has led to a greater appreciation of its importance particularly in a world that is largely shaped by human activity. This includes climate change, pollution, and habitat loss that hinders many species from adapting. Understanding evolution can help us make better decisions about the future of our planet and the lives of its inhabitants.