The Academy's Evolution Site
Biological evolution is one of the most central concepts in biology. The Academies are involved in helping those interested in the sciences understand evolution theory and how it can be applied across all areas of scientific research.
This site offers a variety of sources for teachers, students, and general readers on evolution. It also includes important video clips from NOVA and WGBH produced science programs on DVD.
Tree of Life
The Tree of Life is an ancient symbol of the interconnectedness of life. It is used in many religions and cultures as an emblem of unity and love. It also has practical applications, like providing a framework for understanding the history of species and how they react to changes in environmental conditions.
Early approaches to depicting the biological world focused on the classification of species into distinct categories that were distinguished by physical and metabolic characteristics1. These methods, which rely on sampling of different parts of living organisms or on sequences of short fragments of their DNA, significantly increased the variety that could be represented in a tree of life2. However these trees are mainly made up of eukaryotes. Bacterial diversity is not represented in a large way3,4.
Genetic techniques have significantly expanded our ability to represent the Tree of Life by circumventing the need for direct observation and experimentation. In particular, molecular methods allow us to build trees using sequenced markers such as the small subunit of ribosomal RNA gene.
Despite the rapid expansion of the Tree of Life through genome sequencing, a large amount of biodiversity remains to be discovered. 무료 에볼루션 is particularly true for microorganisms that are difficult to cultivate and are usually only represented in a single sample5. A recent study of all known genomes has produced a rough draft of the Tree of Life, including a large number of archaea and bacteria that are not isolated and whose diversity is poorly 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. The information is useful in a variety of ways, such as identifying new drugs, combating diseases and enhancing crops. This information is also extremely beneficial in conservation efforts. It can aid biologists in identifying the areas most likely to contain cryptic species with important metabolic functions that could be vulnerable to anthropogenic change. Although funds to protect biodiversity are crucial but the most effective way to preserve the world's biodiversity is for more people living in developing countries to be empowered with the necessary knowledge to act locally to promote conservation from within.
Phylogeny
A phylogeny (also known as an evolutionary tree) illustrates the relationship between species. Scientists can build an phylogenetic chart which shows the evolution of taxonomic groups based on molecular data and morphological similarities or differences. The role of phylogeny is crucial in understanding biodiversity, genetics and evolution.
A basic phylogenetic tree (see Figure PageIndex 10 Finds the connections between organisms that have similar traits and have evolved from an ancestor that shared traits. These shared traits may be analogous or homologous. Homologous characteristics are identical in terms of their evolutionary paths. Analogous traits could appear similar however they do not have the same ancestry. Scientists arrange similar traits into a grouping referred to as a Clade. All members of a clade share a characteristic, like amniotic egg production. They all evolved from an ancestor that had these eggs. A phylogenetic tree is built by connecting the clades to identify the species which are the closest to one another.
Scientists make use of molecular DNA or RNA data to create a phylogenetic chart that is more accurate and detailed. This information is more precise and provides evidence of the evolution of an organism. Researchers can utilize Molecular Data to calculate the age of evolution of organisms and identify how many organisms share a common ancestor.
The phylogenetic relationship can be affected by a variety of factors that include the phenomenon of phenotypicplasticity. This is a kind of behavior that alters as a result of specific environmental conditions. This can cause a characteristic to appear more similar in one species than another, obscuring the phylogenetic signal. This problem can be mitigated by using cladistics, which is a a combination of analogous and homologous features in the tree.
In addition, phylogenetics helps determine the duration and speed of speciation. This information can assist conservation biologists in making decisions about which species to safeguard from disappearance. In the end, it is the preservation of phylogenetic diversity which will create an ecosystem that is complete and balanced.
Evolutionary Theory
The central theme in evolution is that organisms alter over time because of their interactions with their environment. Many scientists have proposed theories of evolution, such as the Islamic naturalist Nasir al-Din al-Tusi (1201-274) who believed that an organism would develop according to its own requirements as well as the Swedish taxonomist Carolus Linnaeus (1707-1778), who created the modern hierarchical system of taxonomy and Jean-Baptiste Lamarck (1844-1829), who suggested 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, were brought together to form a modern synthesis of evolution theory. This describes how evolution happens through the variations in genes within the population and how these variants change over time as a result of natural selection. This model, known as genetic drift or mutation, gene flow, and sexual selection, is a cornerstone of modern evolutionary biology and can be mathematically explained.
Recent discoveries in the field of evolutionary developmental biology have shown how variation can be introduced to a species by genetic drift, mutations or reshuffling of genes in sexual reproduction and migration between populations. These processes, along with others like directional selection and genetic erosion (changes in the frequency of an individual's genotype over time) can result in evolution that is defined as change 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 sell into all areas of biology education could increase student understanding of the concepts of phylogeny as well as evolution. A recent study by Grunspan and colleagues, for example, showed that teaching about the evidence for evolution increased students' understanding of evolution in a college-level biology course. 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
Traditionally, scientists have studied evolution through looking back--analyzing fossils, comparing species and studying living organisms. But evolution isn't a thing that occurred in the past, it's an ongoing process that is that is taking place in the present. Bacteria evolve and resist antibiotics, viruses reinvent themselves and escape new drugs, and animals adapt their behavior to a changing planet. The changes that result are often evident.
However, it wasn't until late 1980s that biologists realized that natural selection can be observed in action as well. The key is that various traits confer different rates of survival and reproduction (differential fitness), and can be passed down from one generation to the next.
In the past, if one particular allele - the genetic sequence that determines coloration--appeared in a group of interbreeding organisms, it could quickly become more prevalent than all other alleles. In time, this could mean that the number of moths that have 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 an organism, like bacteria, has a rapid generation turnover. Since 1988, Richard Lenski, a biologist, has studied twelve populations of E.coli that are descended from one strain. The samples of each population have been collected regularly, and more than 500.000 generations of E.coli have passed.
Lenski's research has demonstrated that mutations can alter the rate at which change occurs and the rate of a population's reproduction. It also shows evolution takes time, a fact that is difficult for some to accept.
Microevolution can be observed in the fact that mosquito genes that confer resistance to pesticides are more prevalent in populations where insecticides are used. That's because the use of pesticides creates a pressure that favors those who have resistant genotypes.
The rapid pace of evolution taking place has led to an increasing appreciation of its importance in a world shaped by human activity--including climate changes, pollution and the loss of habitats that prevent many species from adapting. Understanding the evolution process can assist you in making better choices regarding the future of the planet and its inhabitants.