The Academy's Evolution Site
Biology is a key concept in biology. The Academies have been active for a long time in helping those interested in science comprehend the concept of evolution and how it influences all areas of scientific exploration.
This site provides teachers, students and general readers with a wide range of learning resources about evolution. It contains key 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 all life. It is a symbol of love and unity across many cultures. It also has practical applications, such as providing a framework to understand the history of species and how they respond to changing environmental conditions.
The earliest attempts to depict the world of biology focused on categorizing organisms into distinct categories that had been distinguished by physical and metabolic characteristics1. These methods, which relied on sampling of different parts of living organisms, or short fragments of their DNA, greatly increased the variety of organisms that could be represented in a tree of life2. However, these trees are largely made up of eukaryotes. Bacterial diversity remains vastly underrepresented3,4.
By avoiding the necessity for direct observation and experimentation genetic techniques have enabled us to depict the Tree of Life in a more precise way. Particularly, molecular techniques enable us to create trees using sequenced markers like the small subunit of ribosomal RNA gene.
Despite the massive growth of the Tree of Life through genome sequencing, a lot of biodiversity awaits discovery. This is especially true for microorganisms that are difficult to cultivate and are typically found in a single specimen5. A recent analysis of all genomes resulted in an initial draft of the Tree of Life. This includes a large number of bacteria, archaea and other organisms that haven't yet been identified or whose diversity has not been thoroughly understood6.
The expanded Tree of Life is particularly useful in assessing the diversity of an area, helping to determine if specific habitats require protection. This information can be used in a variety of ways, from identifying the most effective treatments to fight disease to enhancing crop yields. It is also valuable to conservation efforts. It helps biologists discover areas that are likely to have species that are cryptic, which could have important metabolic functions, and could be susceptible to changes caused by humans. Although funding to protect biodiversity are crucial however, the most effective method to ensure the preservation of biodiversity around the world is for more people living in developing countries to be empowered with the necessary knowledge to take action locally to encourage conservation from within.
Phylogeny
A phylogeny (also called an evolutionary tree) shows the relationships between organisms. By using molecular information as well as morphological similarities and distinctions, or ontogeny (the process of the development of an organism) scientists can create a phylogenetic tree which illustrates the evolutionary relationship between taxonomic categories. The concept of phylogeny is fundamental to understanding the evolution of biodiversity, evolution and genetics.
A basic phylogenetic Tree (see Figure PageIndex 10 ) determines the relationship between organisms with similar traits that have evolved from common ancestors. These shared traits could be analogous or homologous. Homologous traits are similar in their underlying evolutionary path and analogous traits appear similar, but do not share the identical origins. Scientists arrange similar traits into a grouping referred to as a clade. All organisms in a group share a characteristic, for example, amniotic egg production. Evolution KR derived from an ancestor who had these eggs. A phylogenetic tree can be constructed by connecting clades to identify the species which are the closest to each other.
For a more detailed and accurate phylogenetic tree, scientists use molecular data from DNA or RNA to identify the connections between organisms. This information is more precise and provides evidence of the evolution history of an organism. Researchers can utilize Molecular Data to calculate the evolutionary age of organisms and determine the number of organisms that have a common ancestor.
Phylogenetic relationships can be affected by a variety of factors, including the phenomenon of phenotypicplasticity. This is a type behaviour that can change as a result of specific environmental conditions. This can cause a characteristic to appear more similar to one species than another and obscure the phylogenetic signals. However, this problem can be reduced by the use of methods such as cladistics that combine analogous and homologous features into the tree.
Furthermore, phylogenetics may help predict the duration and rate of speciation. This information can help conservation biologists make decisions about which species to protect from the threat of extinction. In the end, it is the preservation of phylogenetic diversity that will lead to 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. A variety of theories about evolution have been proposed by a variety of scientists, including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who envisioned an organism developing slowly according to its needs as well as the Swedish botanist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical taxonomy, as well as Jean-Baptiste Lamarck (1744-1829) who suggested that the use or misuse of traits causes changes that could be passed onto offspring.
In the 1930s and 1940s, ideas from different fields, including genetics, natural selection and particulate inheritance, were brought together to create a modern synthesis of evolution theory. This explains how evolution is triggered by the variation of genes in the population, and how these variations change with time due to natural selection. This model, which includes mutations, genetic drift in gene flow, and sexual selection is mathematically described mathematically.
Recent developments in the field of evolutionary developmental biology have demonstrated that genetic variation can be introduced into a species by genetic drift, mutation, and reshuffling of genes in sexual reproduction, and also by migration between populations. These processes, along with others such as directional selection and gene erosion (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 an individual).
Incorporating evolutionary thinking into all areas of biology education can increase student understanding of the concepts of phylogeny and evolutionary. In a recent study by Grunspan and colleagues. It was demonstrated that teaching students about the evidence for evolution boosted their understanding of evolution in the course of a college biology. To find out more about how to teach about evolution, please look up The Evolutionary Potential in all Areas of Biology and Thinking Evolutionarily A Framework for Infusing Evolution in Life Sciences Education.
Evolution in Action
Traditionally scientists have studied evolution through looking back--analyzing fossils, comparing species and observing living organisms. Evolution isn't a flims event; it is a process that continues today. Viruses evolve to stay away from new antibiotics and bacteria transform to resist antibiotics. Animals adapt their behavior as a result of a changing environment. The results are often evident.
It wasn't until late 1980s that biologists began to realize that natural selection was also at work. The main reason is that different traits confer a different rate of survival and reproduction, and can be passed on from one generation to the next.
In the past, when one particular allele - the genetic sequence that determines coloration--appeared in a group of interbreeding organisms, it might rapidly become more common than all other alleles. Over time, this would mean that the number of moths that have 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 one strain. Samples from each population have been taken regularly, and more than 500.000 generations of E.coli have been observed to have passed.
Lenski's work has shown that mutations can alter the rate at which change occurs and the effectiveness of a population's reproduction. It also proves that evolution is slow-moving, a fact that many find hard to accept.
Microevolution can be observed in the fact that mosquito genes for resistance to pesticides are more prevalent in areas where insecticides have been used. This is because the use of pesticides causes a selective pressure that favors those with resistant genotypes.
The rapidity of evolution has led to an increasing appreciation of its importance particularly in a world that is largely shaped by human activity. This includes the effects of climate change, pollution and habitat loss that prevents many species from adapting. Understanding the evolution process can assist you in making better choices about the future of our planet and its inhabitants.