The Academy's Evolution Site
The concept of biological evolution is a fundamental concept in biology. The Academies have long been involved in helping people who are interested in science comprehend the theory of evolution and how it influences all areas of scientific exploration.
This site provides a range of resources for students, teachers as well as general readers about 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 is seen in a variety of spiritual traditions and cultures as an emblem of unity and love. It has numerous practical applications as well, such as providing a framework to understand the evolution of species and how they respond to changing environmental conditions.
Early approaches to depicting the world of biology focused on categorizing organisms into distinct categories which were distinguished by physical and metabolic characteristics1. These methods, which relied on the sampling of various parts of living organisms, or sequences of short fragments of their DNA, significantly increased the variety that could be represented in a tree of life2. However the trees are mostly composed of eukaryotes; bacterial diversity is still largely unrepresented3,4.
By avoiding the necessity for direct experimentation and observation, genetic techniques have made it possible to depict the Tree of Life in a much more accurate way. Particularly, molecular techniques allow us to construct trees by using sequenced markers such as the small subunit ribosomal gene.
Despite the rapid growth of the Tree of Life through genome sequencing, a large amount of biodiversity remains to be discovered. This is especially relevant to microorganisms that are difficult to cultivate and which are usually only found in one sample5. A recent analysis of all genomes has produced an initial draft of a Tree of Life. This includes a variety of bacteria, archaea and other organisms that haven't 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, helping to determine if certain habitats require special protection. This information can be used in a variety of ways, including finding new drugs, fighting diseases and enhancing crops. This information is also beneficial in conservation efforts. It can aid biologists in identifying areas that are likely to be home to cryptic species, which may have vital metabolic functions and be vulnerable to the effects of human activity. While funds to protect biodiversity are important, the most effective method to preserve the world's biodiversity is to empower more people in developing countries with the knowledge they need to take action locally and encourage conservation.
Phylogeny
A phylogeny is also known as an evolutionary tree, shows the relationships between various groups of organisms. Utilizing molecular data, morphological similarities and differences, or ontogeny (the process of the development of an organism) scientists can create a phylogenetic tree that illustrates the evolutionary relationships between taxonomic groups. Phylogeny is essential in understanding biodiversity, evolution and genetics.
A basic phylogenetic tree (see Figure PageIndex 10 ) is a method of identifying the relationships between organisms that share similar traits that evolved from common ancestors. These shared traits can be analogous or homologous. Homologous traits are similar in their evolutionary origins and analogous traits appear similar, but do not share the identical origins. Scientists group similar traits together into a grouping known as a Clade. For example, all of the organisms in a clade share the trait of having amniotic egg and evolved from a common ancestor which had eggs. The clades are then connected to create a phylogenetic tree to determine which organisms have the closest connection to each other.
For a more detailed and precise phylogenetic tree scientists rely on molecular information from DNA or RNA to establish the relationships between organisms. This information is more precise than morphological information and gives evidence of the evolutionary history of an individual or group. The analysis of molecular data can help researchers identify the number of organisms that have the same ancestor and estimate their evolutionary age.
The phylogenetic relationships of organisms can be influenced by several factors, including phenotypic plasticity an aspect of behavior that alters in response to unique environmental conditions. This can cause a trait to appear more similar to one species than other species, which can obscure the phylogenetic signal. However, this problem can be solved through the use of techniques such as cladistics which combine analogous and homologous features into the tree.
In addition, phylogenetics can help predict the duration and rate of speciation. This information will assist conservation biologists in making choices about which species to save from extinction. In the end, it is the conservation of phylogenetic variety that will lead to an ecosystem that is complete and balanced.
Evolutionary Theory
The main idea behind evolution is that organisms change over time as a result of their interactions with their environment. Many theories of evolution have been proposed by a wide range of scientists including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who envisioned an organism developing gradually according to its needs, the Swedish botanist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical taxonomy Jean-Baptiste Lamarck (1744-1829) who suggested that the use or non-use of traits can cause changes that can be passed onto offspring.
In the 1930s & 1940s, concepts from various fields, such as genetics, natural selection and particulate inheritance, merged to create a modern synthesis of evolution theory. This defines how evolution happens through the variation of genes in the population and how these variants alter over time due to natural selection. This model, which is known as genetic drift mutation, gene flow and sexual selection, is the foundation of the current evolutionary biology and can be mathematically explained.
Recent advances in the field of evolutionary developmental biology have demonstrated how variations can be introduced to a species by genetic drift, mutations or reshuffling of genes in sexual reproduction and the movement between populations. These processes, as well as others like directional selection and genetic erosion (changes in the frequency of a genotype over time), can lead to evolution that is defined as change in the genome of the species over time, and also by changes in phenotype over time (the expression of that genotype in an individual).
에볼루션 블랙잭 can better understand the concept of phylogeny through incorporating evolutionary thinking into all aspects of biology. A recent study conducted by Grunspan and colleagues, for instance demonstrated that teaching about the evidence supporting evolution helped students accept the concept of evolution in a college-level biology class. For more information on how to teach about evolution, see The Evolutionary Potential in all Areas of Biology or Thinking Evolutionarily A Framework for Integrating Evolution into Life Sciences Education.
Evolution in Action
Scientists have looked at evolution through the past, studying fossils, and comparing species. They also study living organisms. However, evolution isn't something that happened in the past; it's an ongoing process that is happening in the present. Viruses evolve to stay away from new antibiotics and bacteria transform to resist antibiotics. Animals alter their behavior in the wake of a changing world. The changes that result are often apparent.
It wasn't until the 1980s that biologists began to realize that natural selection was 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 one particular allele, the genetic sequence that defines color in a group of interbreeding organisms, it might rapidly become more common than all other alleles. In time, this could mean that the number of moths with black pigmentation in a group may increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
It is easier to observe evolution when an organism, like bacteria, has a high generation turnover. Since 1988 biologist Richard Lenski has been tracking twelve populations of E. coli that descended from a single strain; samples of each population are taken every day and more than fifty thousand generations have passed.
Lenski's research has revealed that mutations can alter the rate at which change occurs and the efficiency of a population's reproduction. It also shows that evolution takes time--a fact that some people are unable to accept.
Microevolution can also be seen in the fact that mosquito genes that confer resistance to pesticides are more common in populations where insecticides are used. Pesticides create an enticement that favors individuals who have resistant genotypes.
The rapidity of evolution has led to a greater recognition of its importance especially in a planet shaped largely by human activity. This includes the effects of climate change, pollution and habitat loss, which prevents many species from adapting. Understanding the evolution process can help you make better decisions about the future of the planet and its inhabitants.