Tuesday, August 16, 2022

What Is Selective Pressure In Biology

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Why Control Activity Evolutionary Selection Pressures Affecting The Development Of Physical Activity Genetic And Biological Regulation

Natural Selection – Crash Course Biology #14

J. Timothy Lightfoot

1Huffines Institute of Sports Medicine and Human Performance, Health and Kinesiology Department, Texas A& M University, 356 Blocker Building, 4243 TAMU, College Station, TX 77843, USA


1. Introduction

2. Exercise Endurance and Physical Activity Appear to Have Evolved Separately

It is generally accepted that Homo sapiens initially evolved the anatomical and physiological capability for endurance running approximately 40,00050,000 years ago . However, it is unclear whether the genetic control of physical activity is a derivation from the selected traits that allowed endurance running or whether physical activity evolved as a separate trait. As we have noted elsewhere , it is tempting to suggest that physiological characteristics that increase endurance might also be key components leading to higher voluntary physical activity levels, and thus both exercise endurance and physical activity would have evolved in lockstep with each other. However, two independent lines of evidence suggest that exercise capacity and activity levels did not evolve together.

3. Potential Selection Pressures for the Evolution of Physical Activity Regulation

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Potential selection pressures on activity regulation in humans and possible future effects of food abundance.

4. Applications and Future Directions

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Antibiotic Treatments And Age

We chose carbenicillin, a member of the carboxypenicillin antibiotic family which is known to interfere with cellular growth by preventing cross-linking of peptidoglycan units during cell-wall synthesis , as an age-dependent selective agent. Bacteria often survive antibiotic treatments by stopping cellular divisions, but not elongation, during exposures to cytotoxic agents . Furthermore, analogs of carbenicillin have been shown to specifically target cells undergoing cellular division , suggesting that division rather than cell wall synthesis is the main factor that increases the sensitivity to antibiotics.

To experimentally test whether carbenicillin affects bacterial cells in an age-dependent manner, we first monitored 18 different populations of E. coli bacteria growing inside a microfluidic device and subjected them to a 20-minutes pulse of a lethal dose carbenicillin every 90 minutes. A fluorescence micrograph of each population was recorded every minute and each image underwent processing to extract the physiological properties of each cell. Cells grew and divided in a monolayer within the chambers, and were removed either by antibiotic-mediated killing or by flow death, i.e. departure from the growth chamber due to cellular growth .

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Proteins Mediating Selective Permeability

Selective permeability is mediated by special proteins that traverse the cellular membrane. They are involved in the movement of ions and small molecules as well as large polymers such as RNA and proteins. This movement can be passive or active â with or without the expenditure of energy.

For instance, ions are transported across selectively permeable membranes through channels and pumps. While channels are for passive transport, ion pumps mediate primary active transport against a concentration gradient, with the hydrolysis of a high-energy phosphate bond.

Active transport can also be coupled with the movement of another molecule. This can either be through a symporter protein â where two molecules are transported in the same direction â or antiporter protein â where molecules are shunted in opposite directions. The principle in both cases is the same â the potential energy stored in an electrochemical gradient is used to drive the transport of another molecule.

Natural Selection In Humans

Natural Selection

The Malaria parasite can exert a selective pressure on populations. This pressure has led to natural selection for erythrocytes carrying the sickle cellhemoglobingenemutation âcausing sickle cell anaemiaâin areas where malaria is a major health concern, because the condition grants some resistance to this infectious disease.

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Organisms Artefacts And Agents

The four options I outlined in the previous section concerned what kind of significance we should attach to function talk in biology. There is another important distinction, orthogonal to this one, that concerns how we are to analyse that talk. This distinction is between theories of biological function that take their inspiration from what I call the artefact model of organic function , and theories that take their inspiration from the agent model of organic function. In the first case, one sees the functions of organic parts as similar in kind to the functions of the parts of artefacts. In the second case, one sees the organism as a whole as akin to an agent aiming at some goal.

The artefact/agent distinction is orthogonal to the fourfold distinction I introduced near the beginning of this essay because, to take just one example, regardless of whether we think function talk in biology is literally true of biological systems, or merely expresses a series of fruitful metaphors, we would still have to decide whether that talk should be analysed and explained in ways that relate organisms to goal-directed systems, or to designed systems, or to both. Almost all contributors to the debate over the past twenty years or so have adopted an artefact-based model of function. Once again, a central aim in this essay is to explore the prospects for agent-based models, and to encourage others to give these accounts a second chance.

Kent A. Peacock, in, 2011

Selective Pressure Drives Research Strategy Evolution

I have been investigating pathogenic streptococci including S. pneumoniae, with a primary focus on the role of streptococcal proteins in disease pathogenesis. As a Ph.D. student in Osaka, Japan, I attempted to detect novel virulence factors using bacterial protein domain information and molecular microbiological techniques. However, the method of analysis often did not produce good results, despite great amounts of effort and time. I questioned whether an effective method to detect important virulence factors could be found.

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Differential Genomic Signatures Of Positive Selection Across Native Mexican Clusters

The Number of Segregating sites by Length and the H12 statistics were calculated on the phased nonimputed NMDP data set for each of the identified population clusters. We then used the obtained nSL and H12 genome-wide distributions to implement a gene-network approach aimed at inferring the adaptive evolution of each cluster. In particular, the most reliable selection signatures were identified as those ascribable to biological functions putatively targeted by widespread natural selection according to results from the nSL statistics that were supported also by the H12 test . The rationale behind the independent investigation of the adaptive evolution of each cluster was that NM populations belonging to the same genetic group have presumably experienced similar environmental and/or cultural selective pressures, as conceivable according to a large body of anthropological, archeological, and historical evidence . The sole exception was represented by NMC populations , who were analyzed separately due to their significant genetic differentiation and because they have long maintained different lifestyles despite having encountered similar environmental conditions in Aridoamerica .

Toward Generalized Dynamics Of Variation

Mutations and Natural Selection | Evolution | Biology | FuseSchool

The theory of natural selection as it is used to describe biological evolution can be generalized to any kind of systemic evolution. It suffices to consider a system susceptible to variations and an environment exerting a selective pressure on the system: only those configurations of the system will maintain which are fit or adapted to the environment. The evolution system can be likened to a problem solver, generating possible solutions by trial to a problem posed by the environment: how to be optimally adapted? A problem arises as soon as adaptation is not optimal, i.e., the system is not completely stable or invariant with respect to the environment. The larger the instability, the more serious the problem, and the more variation the system must undergo before it reaches a new equilibrium. It does not suffice to blindly try out possibilities, in the hope that accidentally one of them might prove to be the optimal solution: the chances that this would succeed are very small. You can enhance your chances by looking for intermediate steps, i.e., relatively easy-to-find problem states or configurations, which are not final solutions but which are somehow closer to the goal than the configuration you started with. This is what also happens during natural selection. For the continuation of this problem, see Heylighen .

Tom Ray, Joseph Hart, in, 2003

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The Importance Of Mimicry To Evolutionary Theory

The mimicry hypothesis emerged in the middle of the Darwinian controversy and provided an ideal test case for the views of Charles Darwin and his contemporary Alfred Russel Wallace on the operation of natural selection in the evolutionary change of living organisms. It is now quite evident that the basic theory of natural selection is correct and that the theory is strengthened by many detailed studies of the process by which a mimetic resemblance is brought about and selected for. In addition, investigating suitable cases of mimicry provides important insight into the evolution of signals and the semantization process by which signals get their meaning.

Structure Of Selectively Permeable Membranes

Cell membranes are not easily visualized using light microscopes. Therefore, hypotheses about their existence only arose in the late 19th century, nearly two hundred years after the first cells has been observed. At various points, different models have attempted to explain how the structure of the membrane supports its function. Initially, the membrane was supposed to be a simple lipid layer demarcating the cytosol from the extracellular region. Afterwards, models included semipermeable gel-like regions in a lipid sea to explain the movement of water but not charged particles. Thereafter, the presence of pores was proposed, allowing small molecules to move freely.

Currently the cell membrane is said to be made of a selectively permeable phospholipid bilayer whose hydrophillic domains face the aqueous environments inside and outside the cell, and hydrophobic domains face each other to form a bilayer. This lipid bilayer is punctuated by cholesterol molecules, glycolipids, and proteins that are either anchored or traverse the entire membrane. These proteins form channels, pores or gates to maintain selective permeability of ions, signaling molecules and macromolecules based on the requirements of the cell.

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Survival Mechanisms To Abiotic Stresses

During evolution, plants have formed diverse adaptive mechanisms to survive in the adverse environmental conditions. High salinity represents one of most common abiotic stresses faced by plants. Exposure to high salinity markedly limits the growth and production of plants due to induction of osmotic, oxidative, and temperature stresses . Although the molecular mechanisms used by plants to overcome high salinity challenge are not fully understood, recent advances have begun to identify key pathways and molecules , many of which regulate the ionic balance . For example, Na+ has been shown to be important for maintenance of intracellular K+ concentrations, and Na+/K+ homeostasis is crucial for plant growth and development. At high salt concentrations, plants reduce Na+ influx and/or increase Na+ efflux to maintain homeostasis of intracellular Na+ concentrations . Genes involved in the response to high salinity stress include the glycosyltransferase Qua1, which modulates Ca2+ levels as part of the response to high salinity stress . Overexpression of AtZFP1, a CCCH type zinc finger protein, promotes tolerance to high salinity by regulating expression of ion transport proteins . A subset of genes with ion-independent functions have also been shown to be critical for tolerance to high salinity . For example, Arabidopsis plants overexpressing glutathione S-transferase are more tolerant to high salinity stress .

Caflp For Studying The Molecular Evolution Of Microbes

OpenStax: Biology

In general terms, nucleotide substitutions that are introduced inadvertently, i.e., due to replication infidelities, or are brought forward under selective pressure, constitute a major source for naturally occuring DNA polymorphisms. However, genetic diversity in prokaryotes appears to be driven largely by a number of dynamic processes that enable them to react swiftly to changes in their environment. To accomplish this adapt-to-survive strategy, microbes have a plethora of routes at their disposal to acquire beneficial, or eliminate superfluous, genetic material, and to re-shuffle genes that need to be expressed at short notice. This structural plasticity of microbial genomes has been the subject of numerous investigations, particularly in the light of the recent spread of antibiotic resistance genes and the intra- and inter-species transfer of virulence determinants. However, such investigations are focused mainly on one particular gene or set of genes, and reports on whole genome analysis in the context of evolutionary studies on microbes are very scarce .

A. Leoni Swart, Hubert Hilbi, in, 2022

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Theres A Lot To Learn When A Gene Turns Green

E. coli

Some genes might not mind a bit of extra pressure when it comes to evolution.

A Swiss team led by Andreas Wagner of the University of Zurich has demonstrated evolution of a yellow gene to green in Escherichia coli a common bacteria that lives in the gut. Strong selective pressure caused the gene to evolve more quickly, because it developed a robust protein that helped it to do so efficiently.

This could be one of the first experimentally demonstrated examples of selection helping a gene to be better at evolving, instead of crippling it. This is very hard to observe because of how long evolution usually takes.

To our knowledge, this is the first experimental proof that selection can drive the ability to adapt in a Darwinian sense and increase evolvability, says Wagner. There are still people out there who question whether evolution is real. But we dont just look at fossils where we have a historical record. We observe evolution in the laboratory.

The findings are described in a paper in the journal Science.

Strong selective pressure occurs when only a few individuals in a population can reproduce, usually because the environment is harsh, and a very specific set of genes is needed to survive to adulthood. However, this can often mean that the genome doesnt get a chance to collect useful mutations, and proteins can become weak.

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What Are Selection Pressures

Selection pressures are factors that exist in an environment that make it easier for some organisms to survive and others less likely to survive. For example, many arctic or antarctic animals have flubber that are favourable in those cold conditions because it retains more heat, imagine how easy it would be to freeze if they didnt have it!

This video goes through selection pressures in more depth.

Abiotic relates to non-living factors while biotic relates to living factors . Selection pressures can be abiotic or biotic. This video looks at abiotic and biotic factors.

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Resistance To Herbicides And Pesticides

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Just as with the development of antibiotic resistance in bacteria, resistance to pesticides and herbicides has begun to appear with commonly used agricultural chemicals. For example:

  • In the US, studies have shown that fruit flies that infest orange groves were becoming resistant to malathion, a pesticide used to kill them.
  • In Hawaii and Japan, the diamondback moth developed a resistance to Bacillus thuringiensis, which is used in several commercial crops including Bt corn, about three years after it began to be used heavily.
  • In England, rats in certain areas have developed such a strong resistance to rat poison that they can consume up to five times as much of it as normal rats without dying.
  • DDT is no longer effective in controlling mosquitoes that transmit malaria in some places, a fact that contributed to a resurgence of the disease.
  • In the southern United States, the weed Amaranthus palmeri, which interferes with production of cotton, has developed widespread resistance to the herbicide glyphosate.
  • In the Baltic Sea, decreases in salinity has encouraged the emergence of a new species of brown seaweed, Fucus radicans.

Examples Of Evolution: Selective Pressures And Adaptation

Natural selection and evolution | High school biology | Khan Academy

Natural selection works on individuals within a population, with the end result that a variation that provides benefit to the individual will become more prevalent in the population. Natural selection is one variable in evolution, but it is not the only type of selection. Other types of selection include artificial, sexual and kin selection. These selective pressures result in adaptions – particular lifestyles or body plans that provide an advantage in a specific environment.

  • Guppy coloration: Guppies are fresh water tropical fish that are favorites in aquariums because the males are beautifully colored. In the wild, guppies live in streams where they are the favorite snacks of many larger fish. John Endler studied guppies in Trinidad and found that the presence of absence of predators influenced the amount of coloring in male guppies. This is an example of the intersection of two evolutionary forces: natural selection and sexual selection.
  • Understanding Evolution: Artificial Selection in the Lab
  • Mimicry: Mimicry usually refers to the way some organisms protect themselves by appearing like another poisonous or dangerous organism. Another version of mimicry is used by both predators and prey when a body plan copies environment, such as a walking stick insect. Although the basic concept is straightforward, mimicry is a complex phenomenon in which a variety of evolutionary forces come into play.

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