에볼루션 바카라 체험 is one of the most fundamental concepts in biology. The Academies have been active for a long time in helping those interested in science understand the theory of evolution and how it permeates all areas of scientific exploration.

This site provides a range of sources for teachers, students, and general readers on 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 symbolizes the interconnectedness of all life. It is seen in a variety of religions and cultures as an emblem of unity and love. It also has many practical applications, such as providing a framework for understanding the evolution of species and how they respond to changing environmental conditions.

Early attempts to describe the biological world were founded on categorizing organisms on their metabolic and physical characteristics. These methods, which depend on the sampling of different parts of organisms or DNA fragments have greatly increased the diversity of a tree of Life2. However these trees are mainly composed of eukaryotes; bacterial diversity remains vastly underrepresented3,4.

Genetic techniques have significantly expanded our ability to represent the Tree of Life by circumventing the need for direct observation and experimentation. Particularly, molecular methods allow us to construct trees using sequenced markers like the small subunit of ribosomal RNA gene.

Despite the rapid expansion of the Tree of Life through genome sequencing, a lot of biodiversity awaits discovery. This is particularly the case for microorganisms which are difficult to cultivate and which are usually only found in a single specimen5. A recent study of all genomes known to date has produced a rough draft version of the Tree of Life, including numerous bacteria and archaea that have not been isolated, and whose diversity is poorly understood6.

The expanded Tree of Life can be used to evaluate the biodiversity of a specific region and determine if specific habitats need special protection. This information can be used in a variety of ways, from identifying new treatments to fight disease to enhancing crop yields. The information is also valuable for conservation efforts. It can help biologists identify areas that are most likely to be home to species that are cryptic, which could have vital metabolic functions, and could be susceptible to the effects of human activity. Although funds to safeguard biodiversity are vital however, the most effective method to ensure the preservation of biodiversity around the world is for more people in developing countries to be empowered with the necessary knowledge to act locally to promote conservation from within.

Phylogeny

A phylogeny (also called an evolutionary tree) depicts the relationships between different organisms. By using molecular information, morphological similarities and differences, or ontogeny (the process of the development of an organism) scientists can construct a phylogenetic tree that illustrates the evolutionary relationship between taxonomic categories. The phylogeny of a tree plays an important role in understanding genetics, biodiversity and evolution.

A basic phylogenetic tree (see Figure PageIndex 10 Determines the relationship between organisms that have similar characteristics and have evolved from an ancestor with common traits. These shared traits may be analogous, or homologous. Homologous traits share their evolutionary roots, while analogous traits look like they do, but don't have the same ancestors. Scientists put similar traits into a grouping called a the clade. For instance, all of the organisms in a clade share the trait of having amniotic eggs. They evolved from a common ancestor which had eggs. The clades are then linked to create a phylogenetic tree to identify organisms that have the closest connection to each other.

To create a more thorough and accurate phylogenetic tree, scientists use molecular data from DNA or RNA to determine the relationships among organisms. This information is more precise than the morphological data and provides evidence of the evolution history of an organism or group. Researchers can utilize Molecular Data to determine the age of evolution of living organisms and discover the number of organisms that share the same ancestor.

The phylogenetic relationships between species can be influenced by several factors including phenotypic plasticity, a kind of behavior that changes in response to unique environmental conditions. This can cause a trait to appear more similar to one species than to the other which can obscure the phylogenetic signal. This problem can be mitigated by using cladistics. This is a method that incorporates the combination of homologous and analogous traits in the tree.

Furthermore, phylogenetics may help predict the length and speed of speciation. This information can assist conservation biologists in making choices about which species to protect from disappearance. In the end, it's the preservation of phylogenetic diversity which will lead to an ecologically balanced and complete ecosystem.

Evolutionary Theory

The fundamental concept of evolution is that organisms acquire distinct characteristics over time as a result of their interactions with their environments. Many scientists have proposed theories of evolution, including the Islamic naturalist Nasir al-Din al-Tusi (1201-274) who believed that an organism could develop according to its own requirements, the Swedish taxonomist Carolus Linnaeus (1707-1778) who developed the modern hierarchical taxonomy and Jean-Baptiste Lamarck (1844-1829), who suggested that the use or absence of traits can lead to changes that are passed on to the

In the 1930s & 1940s, concepts from various areas, including natural selection, genetics & particulate inheritance, came together to form a contemporary synthesis of evolution theory. This describes how evolution happens through the variation of genes in the population and how these variations change with time due to natural selection. This model, known as genetic drift or mutation, gene flow and sexual selection, is a cornerstone of modern evolutionary biology and is mathematically described.

Recent discoveries in the field of evolutionary developmental biology have shown that variation can be introduced into a species via genetic drift, mutation, and reshuffling of genes in sexual reproduction, as well as through migration between populations. These processes, as well as others, such as directional selection and gene erosion (changes in frequency of genotypes over time) can lead to evolution. Evolution is defined by changes in the genome over time and changes in phenotype (the expression of genotypes in an individual).


Students can better understand the concept of phylogeny through incorporating evolutionary thinking into all aspects of biology. In a recent study conducted by Grunspan and colleagues. It was demonstrated that teaching students about the evidence for evolution boosted their acceptance of evolution during an undergraduate biology course. For more details on how to teach evolution, see The Evolutionary Power of Biology in all Areas of Biology or Thinking Evolutionarily: a Framework for Integrating Evolution into Life Sciences Education.

Evolution in Action

Scientists have traditionally studied evolution through looking back in the past--analyzing fossils and comparing species. They also observe living organisms. However, evolution isn't something that occurred in the past, it's an ongoing process that is taking place today. Bacteria mutate and resist antibiotics, viruses re-invent themselves and are able to evade new medications, and animals adapt their behavior in response to the changing environment. The resulting changes are often evident.

However, it wasn't until late-1980s that biologists realized that natural selection can be observed in action as well. The key is that various characteristics result in different rates of survival and reproduction (differential fitness), and can be transferred from one generation to the next.

In the past, if an allele - the genetic sequence that determines color - was found in a group of organisms that interbred, it might become more prevalent than any other allele. As time passes, that could mean the number of black moths in a population could increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.

The ability to observe evolutionary change is much easier when a species has a rapid generation turnover like bacteria. Since 1988, biologist Richard Lenski has been tracking twelve populations of E. coli that descended from a single strain; samples of each are taken regularly and more than 50,000 generations have now passed.

Lenski's work has demonstrated that a mutation can profoundly alter the speed at the rate at which a population reproduces, and consequently, the rate at which it changes. It also shows evolution takes time, a fact that is hard for some to accept.

Microevolution can be observed in the fact that mosquito genes for resistance to pesticides are more prevalent in populations where insecticides are used. This is because the use of pesticides creates a pressure that favors those with resistant genotypes.

The rapid pace at which evolution can take place has led to a growing awareness of its significance in a world that is shaped by human activities, including climate change, pollution, and the loss of habitats that hinder many species from adapting. Understanding evolution can assist you in making better choices about the future of our planet and its inhabitants.