The Advanced Guide To Evolution Site
The Academy's Evolution Site
Biology is a key concept in biology. The Academies are involved in helping those who are interested in the sciences understand evolution theory and how it is incorporated in all areas of scientific research.
This site provides a wide range of resources for students, teachers and general readers of evolution. It contains the most important video clips from NOVA and WGBH-produced science programs on DVD.
Tree of Life
The Tree of Life, an ancient symbol, represents the interconnectedness of all life. It is an emblem of love and harmony in a variety of cultures. It can be used in many practical ways as well, including providing a framework to understand the evolution of species and how they respond to changing environmental conditions.
The earliest attempts to depict the biological world focused on categorizing species into distinct categories that had been identified by their physical and metabolic characteristics1. These methods, based on the sampling of different parts of living organisms, or small fragments of their DNA greatly increased the variety of organisms that could be included in the tree of life2. The trees are mostly composed of eukaryotes, while bacterial diversity is vastly underrepresented3,4.
By avoiding the necessity for direct observation and experimentation genetic techniques have allowed us to represent the Tree of Life in a more precise manner. Particularly, molecular methods allow us to build trees using sequenced markers, such as the small subunit ribosomal RNA gene.
Despite the rapid growth of the Tree of Life through genome sequencing, a large amount of biodiversity is waiting to be discovered. This is especially true for microorganisms that are difficult to cultivate and which are usually only found in one sample5. A recent study of all known genomes has created a rough draft of the Tree of Life, including numerous archaea and bacteria that have not been isolated, and their diversity is not fully understood6.
The expanded Tree of Life is particularly useful in assessing the diversity of an area, assisting to determine if certain habitats require special protection. This information can be utilized in a variety of ways, including finding new drugs, battling diseases and enhancing crops. The information is also useful for conservation efforts. It can help biologists identify areas most likely to be home to cryptic species, which may have vital metabolic functions and be vulnerable to the effects of human activity. While funding to protect biodiversity are important, the most effective method to protect the world's biodiversity is to equip more people in developing countries with the information they require to act locally and promote conservation.
Phylogeny
A phylogeny is also known as an evolutionary tree, reveals the connections between groups of organisms. By using molecular information similarities and differences in morphology or ontogeny (the course of development of an organism), scientists can build an phylogenetic tree that demonstrates the evolution of taxonomic categories. Phylogeny is crucial in understanding evolution, biodiversity and genetics.
A basic phylogenetic tree (see Figure PageIndex 10 ) determines the relationship between organisms with similar traits that have evolved from common ancestral. These shared traits could be analogous or homologous. Homologous characteristics are identical in terms of their evolutionary paths. Analogous traits might appear like they are, but they do not have the same origins. Scientists combine similar traits into a grouping known as a the clade. All organisms in a group share a trait, such as amniotic egg production. They all derived from an ancestor with these eggs. The clades are then linked to form a phylogenetic branch that can determine which organisms have the closest relationship to.
For a more precise and accurate phylogenetic tree scientists make use of molecular data from DNA or RNA to identify the relationships between organisms. This data is more precise than morphological data and provides evidence of the evolution history of an individual or group. Researchers can utilize Molecular Data to estimate the evolutionary age of organisms and identify the number of organisms that have a common ancestor.
Phylogenetic relationships can be affected by a number of factors, including phenotypicplasticity. This is a type behaviour that can change in response to specific environmental conditions. This can cause a particular trait to appear more similar to 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 the combination of homologous and analogous features in the tree.
Additionally, phylogenetics can help predict the time and pace of speciation. This information will assist conservation biologists in deciding which species to save from extinction. It is ultimately the preservation of phylogenetic diversity which will result in a complete and balanced ecosystem.
Evolutionary Theory
The fundamental concept in evolution is that organisms change over time due to their interactions with their environment. A variety of theories about evolution have been developed by a wide variety of scientists such as the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who envisioned an organism developing gradually according to its needs and needs, the Swedish botanist Carolus Linnaeus (1707-1778) who designed modern hierarchical taxonomy, and Jean-Baptiste Lamarck (1744-1829) who suggested that the use or non-use of traits causes changes that can be passed onto offspring.
In the 1930s and 1940s, concepts from various fields, including genetics, natural selection and particulate inheritance, merged to create a modern synthesis of evolution theory. This describes how evolution is triggered by the variation in genes within the population, and how these variants alter over time due to natural selection. This model, called genetic drift mutation, gene flow and sexual selection, is a key element of the current evolutionary biology and can be mathematically explained.
Recent developments in the field of evolutionary developmental biology have revealed how variations can be introduced to a species by genetic drift, mutations or reshuffling of genes in sexual reproduction, and even migration between populations. These processes, along with other ones like directional selection and genetic erosion (changes in the frequency of a genotype over time) can lead to evolution, which is defined by change in the genome of the species over time and also the change in phenotype over time (the expression of the genotype in an individual).
Incorporating evolutionary thinking into all aspects of biology education can improve student understanding of the concepts of phylogeny and evolution. A recent study by Grunspan and colleagues, for instance demonstrated that teaching about the evidence that supports evolution helped students accept the concept of evolution in a college biology course. To learn more about how to teach about evolution, look up The Evolutionary Potential of All Areas of Biology and 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 happened in the past. It's an ongoing process that is happening right now. The virus reinvents itself to avoid new antibiotics and bacteria transform to resist antibiotics. Animals alter their behavior as a result of a changing environment. The results are usually evident.
But it wasn't until the late-1980s that biologists realized that natural selection could be seen in action, as well. The reason is that different traits confer different rates of survival and reproduction (differential fitness), and can be transferred from one generation to the next.
In the past when one particular allele, the genetic sequence that defines color in a population of interbreeding species, it could quickly become more common than the other alleles. Over time, that would mean the number of black moths in 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 observe evolutionary change when an organism, like bacteria, has a high generation turnover. Since 1988, Richard Lenski, a biologist, has tracked twelve populations of E.coli that are descended from one strain. Samples of each population have been collected frequently and more than 50,000 generations of E.coli have been observed to have passed.
Lenski's work has shown that mutations can alter the rate of change and the effectiveness at which a population reproduces. It also shows that evolution is slow-moving, a fact that some people find hard to accept.
Microevolution is also evident in the fact that mosquito genes for pesticide resistance are more prevalent in areas where insecticides are used. This is because the use of pesticides creates a pressure that favors individuals with resistant genotypes.
The speed at which evolution can take place has led to a growing appreciation of its importance in a world that is shaped by human activity--including climate change, pollution, and the loss of habitats that prevent many species from adjusting. Understanding evolution will aid you in making better decisions about the future of the planet and its inhabitants.