The Academy's Evolution Site
Biological evolution is a central concept in biology. 에볼루션 무료체험 are committed to helping those interested in science to comprehend the evolution theory and how it is permeated across all areas of scientific research.
This site provides students, teachers and general readers with a range of learning resources about 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 all life. It appears in many spiritual traditions and cultures as an emblem of unity and love. It can be used in many practical ways in addition to providing a framework for understanding the history of species and how they respond to changes in environmental conditions.
Early attempts to represent the biological world were based on categorizing organisms based on their metabolic and physical characteristics. These methods, which relied on the 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 a tree of life2. However the trees are mostly made up of eukaryotes. Bacterial diversity is not represented in a large way3,4.
Genetic techniques have significantly expanded our ability to visualize the Tree of Life by circumventing the requirement for direct observation and experimentation. Particularly, molecular methods enable us to create trees by using sequenced markers such as the small subunit ribosomal gene.
The Tree of Life has been greatly expanded thanks to genome sequencing. However there is a lot of biodiversity to be discovered. This is particularly true for microorganisms that are difficult to cultivate, and are usually present in a single sample5. A recent analysis of all genomes produced a rough draft of the Tree of Life. This includes a wide range of bacteria, archaea and other organisms that haven't yet been isolated, or their diversity is not thoroughly understood6.
This expanded Tree of Life is particularly beneficial in assessing the biodiversity of an area, which can help to determine if specific habitats require special protection. The information can be used in a variety of ways, from identifying new treatments to fight disease to enhancing the quality of crop yields. This information is also useful in conservation efforts. It can help biologists identify the areas that are most likely to contain cryptic species that could have important metabolic functions that may be at risk from anthropogenic change. While funds to protect biodiversity are important, the best method to preserve the biodiversity of the world is to equip more people in developing countries with the knowledge they need to act locally and support conservation.
Phylogeny
A phylogeny (also known as an evolutionary tree) illustrates the relationship between organisms. Utilizing 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. The role of phylogeny is crucial in understanding genetics, biodiversity and evolution.
A basic phylogenetic tree (see Figure PageIndex 10 Identifies the relationships between organisms with similar traits and have evolved from an ancestor that shared traits. These shared traits may be homologous, or analogous. Homologous characteristics are identical in their evolutionary paths. Analogous traits could appear like they are however they do not share the same origins. 에볼루션 무료체험 organize similar traits into a grouping called a the clade. For example, all of the organisms in a clade have the characteristic of having amniotic egg and evolved from a common ancestor that had these eggs. A phylogenetic tree is constructed by connecting clades to identify the species who are the closest to one another.
For a more precise and accurate phylogenetic tree scientists use molecular data from DNA or RNA to identify the connections between organisms. This information is more precise than morphological data and gives evidence of the evolutionary background of an organism or group. Researchers can utilize Molecular Data to calculate the evolutionary age of organisms and determine how many species share the same ancestor.
The phylogenetic relationships between species are influenced by many factors, including phenotypic plasticity a kind of behavior that alters in response to unique environmental conditions. This can cause a characteristic to appear more similar to a species than to the other and obscure the phylogenetic signals. This issue can be cured by using cladistics. This is a method that incorporates a combination of homologous and analogous features in the tree.
In addition, phylogenetics can aid in predicting the time and pace of speciation. This information will assist conservation biologists in making decisions about which species to protect from disappearance. Ultimately, it is the preservation of phylogenetic diversity that will lead to an ecologically balanced and complete ecosystem.
Evolutionary Theory
The main idea behind evolution is that organisms alter over time because of their interactions with their environment. Several theories of evolutionary change have been developed by a wide range of scientists such as the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who proposed that a living organism develop slowly in accordance with its needs and needs, 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 cause changes that can be passed on to offspring.
In the 1930s and 1940s, ideas from a variety of fields -- including natural selection, genetics, and particulate inheritance -- came together to form the current synthesis of evolutionary theory which explains how evolution is triggered by the variation of genes within a population, and how these variants change in time as a result of natural selection. This model, known as genetic drift mutation, gene flow, and sexual selection, is a cornerstone of the current evolutionary biology and can be mathematically explained.
Recent advances in the field of evolutionary developmental biology have revealed how variations can be introduced to a species through genetic drift, mutations or reshuffling of genes in sexual reproduction, and even migration between populations. These processes, along with others, such as the directional selection process and the erosion of genes (changes in 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 individuals).
Students can better understand the concept of phylogeny by using evolutionary thinking throughout all aspects of biology. In a recent study conducted by Grunspan et al., it was shown that teaching students about the evidence for evolution boosted their understanding of evolution in a college-level course in biology. To find out more about how to teach about evolution, please see 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
Scientists have studied evolution through looking back in the past, analyzing fossils and comparing species. They also study living organisms. However, evolution isn't something that happened in the past. It's an ongoing process happening today. Bacteria mutate and resist antibiotics, viruses evolve and elude new medications, and animals adapt their behavior to the changing climate. The results are often visible.
However, 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 an individual rate of survival as well as reproduction, and may be passed on from one generation to another.
In the past, if one allele - the genetic sequence that determines color - was found in a group of organisms that interbred, it could become more common than any other allele. Over time, this would 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.
It is easier to see evolution when an organism, like bacteria, has a rapid generation turnover. Since 1988, Richard Lenski, a biologist, has tracked twelve populations of E.coli that are descended from a single strain. The samples of each population have been taken regularly, and more than 50,000 generations of E.coli have been observed to have passed.
Lenski's research has demonstrated that mutations can alter the rate at which change occurs and the efficiency of a population's reproduction. It also proves that evolution takes time--a fact that some find difficult 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. That's because the use of pesticides creates a selective pressure that favors those who have resistant genotypes.
The speed at which evolution can take place has led to an increasing appreciation of its importance in a world that is shaped by human activities, including climate changes, pollution and the loss of habitats that prevent many species from adjusting. Understanding the evolution process will assist you in making better choices regarding the future of the planet and its inhabitants.