The Academy's Evolution Site
Biology is one of the most fundamental concepts in biology. The Academies have long been involved in helping those interested in science comprehend the concept of evolution and how it influences every area of scientific inquiry.
This site provides a range of resources for students, teachers as well as general readers about evolution. It contains important video clips from NOVA and WGBH-produced science programs on DVD.
Tree of Life
The Tree of Life is an ancient symbol that represents the interconnectedness of life. It is an emblem of love and harmony in a variety of cultures. It has numerous practical applications as well, including providing a framework to understand the evolution of species and how they react to changing environmental conditions.
Early attempts to describe the biological world were built on categorizing organisms based on their physical and metabolic characteristics. These methods, which are based on the collection of various parts of organisms, or DNA fragments have greatly increased the diversity of a tree of Life2. However, these trees are largely comprised of eukaryotes, and bacterial diversity is still largely unrepresented3,4.
By avoiding the necessity for direct observation and experimentation, genetic techniques have allowed us to depict the Tree of Life in a more precise way. We can construct trees using molecular methods, such as the small-subunit ribosomal gene.
The Tree of Life has been greatly expanded thanks to genome sequencing. However, there is still much biodiversity to be discovered. This is particularly true for microorganisms that are difficult to cultivate and are typically only present in a single sample5. Recent analysis of all genomes has produced a rough draft of the Tree of Life. This includes a large number of archaea, bacteria, and other organisms that have not yet been isolated, or their diversity is not fully understood6.
This expanded Tree of Life is particularly useful for assessing the biodiversity of an area, assisting to determine whether specific habitats require protection. This information can be used in a variety of ways, such as finding new drugs, fighting diseases and improving crops. It is also valuable in conservation efforts. It can aid biologists in identifying areas that are most likely to be home to species that are cryptic, which could have important metabolic functions, and could be susceptible to human-induced change. While funding to protect biodiversity are essential, the best method to preserve the biodiversity of the world is to equip more people in developing nations with the information they require to act locally and promote conservation.
Phylogeny
A phylogeny, also known as an evolutionary tree, reveals the relationships between different groups of organisms. By using molecular information, morphological similarities and differences, or ontogeny (the process of the development of an organism), scientists can build an phylogenetic tree that demonstrates the evolutionary relationship between taxonomic groups. The role of phylogeny is crucial in understanding biodiversity, genetics and evolution.
A basic phylogenetic tree (see Figure PageIndex 10 ) identifies the relationships between organisms with similar traits that evolved from common ancestral. These shared traits can be either analogous or homologous. Homologous traits are the same in terms of their evolutionary paths. Analogous traits might appear similar however they do not share the same origins. Scientists arrange similar traits into a grouping known as a the clade. For example, all of the species in a clade share the trait of having amniotic eggs. They evolved from a common ancestor who had these eggs. A phylogenetic tree can be built by connecting the clades to identify the organisms that are most closely related to each other.
To create a more thorough and accurate phylogenetic tree, scientists use molecular data from DNA or RNA to identify the relationships among organisms. This information is more precise and gives evidence of the evolution of an organism. Researchers can utilize Molecular Data to calculate the age of evolution of living organisms and discover the number of organisms that have an ancestor common to all.
The phylogenetic relationships between species can be influenced by several factors, including phenotypic flexibility, a kind of behavior that alters in response to specific environmental conditions. This can cause a trait to appear more similar to one species than to another and obscure the phylogenetic signals. However, this issue can be cured by the use of methods such as cladistics which include a mix of analogous and homologous features into the tree.
Additionally, phylogenetics can help predict the time and pace of speciation. This information can assist conservation biologists in making choices about which species to safeguard from disappearance. It is ultimately the preservation of phylogenetic diversity which will create an ecosystem that is complete and balanced.
Evolutionary Theory
The fundamental concept in 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 variety of scientists such as the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who proposed that a living organism develop gradually according to its needs as well as the Swedish botanist Carolus Linnaeus (1707-1778) who developed modern hierarchical taxonomy, and Jean-Baptiste Lamarck (1744-1829) who suggested that use or disuse of traits cause changes that could be passed on to the offspring.
In the 1930s & 1940s, ideas from different fields, including natural selection, genetics & particulate inheritance, came together to create a modern evolutionary theory. This explains how evolution happens through the variations in genes within the population, and how these variants alter over time due to natural selection. This model, which incorporates mutations, genetic drift as well as gene flow and sexual selection, can be mathematically described.
Recent discoveries in the field of evolutionary developmental biology have revealed that variations can be introduced into a species via mutation, genetic drift, and reshuffling of genes during sexual reproduction, and also through the movement of populations. These processes, along with others, such as directionally-selected selection and erosion of genes (changes in frequency of genotypes over time) can lead to evolution. Evolution is defined as changes in the genome over time, as well as changes in phenotype (the expression of genotypes in individuals).
Incorporating evolutionary thinking into all areas of biology education can improve student understanding of the concepts of phylogeny and evolutionary. 에볼루션사이트 by Grunspan and colleagues, for instance, showed that teaching about the evidence for evolution increased students' acceptance of evolution in a college-level biology course. For more information about how to teach evolution look up The Evolutionary Power of Biology 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 study living organisms. However, evolution isn't something that happened in the past. It's an ongoing process that is taking place in the present. Bacteria transform and resist antibiotics, viruses reinvent themselves and are able to evade new medications and animals alter their behavior to the changing environment. The resulting changes are often evident.
It wasn't until the late 1980s that biologists began to realize that natural selection was also in action. The main reason is that different traits confer an individual rate of survival as well as reproduction, and may be passed on from one generation to the next.
In the past when one particular allele, the genetic sequence that defines color in a group of interbreeding species, it could quickly become more prevalent than all other alleles. In time, this could mean that the number of moths sporting 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 track evolutionary change 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 regularly and more than 500.000 generations have passed.
Lenski's work has demonstrated that a mutation can profoundly alter the rate at the rate at which a population reproduces, and consequently the rate at which it changes. It also demonstrates that evolution takes time, a fact that is hard for some to accept.
Microevolution can also be seen in the fact that mosquito genes for pesticide resistance are more common in populations that have used insecticides. Pesticides create a selective pressure which favors individuals who have resistant genotypes.
The rapid pace of evolution taking place has led to a growing recognition of its importance in a world that is shaped by human activities, including climate change, pollution and the loss of habitats that prevent many species from adjusting. Understanding the evolution process will assist you in making better choices about the future of our planet and its inhabitants.