selective pressure

(noun)

Any cause that reduces reproductive success in a proportion of a population, potentially exerts evolutionary pressure or selection pressure.

Related Terms

Examples of selective pressure in the following topics:

  • Shared Features of Bacteria and Archaea

    • Gupta has proposed that the Archaea evolved from Gram-positive bacteria in response to antibiotic selection pressure.
    • His proposal is that the selective pressure towards resistance generated by the Gram-positive antibiotics was eventually sufficient to cause extensive changes in many of the antibiotics' target genes, and that these strains represented the common ancestors of present-day Archaea.
    • The evolution of Archaea in response to antibiotic selection, or any other competitive selective pressure, could also explain their adaptation to extreme environments (such as high temperature or acidity) as the result of a search for unoccupied niches to escape from antibiotic-producing organisms; Cavalier-Smith has made a similar suggestion.

  • Sexual Selection

    • Sexual selection, the selection pressure on males and females to obtain matings, can result in traits designed to maximize sexual success.
    • The selection pressures on males and females to obtain matings is known as sexual selection.
    • The limiting sex is the sex which has the higher parental investment, which therefore faces the most pressure to make a good mate decision.
    • In either case, this variation in reproductive success generates a strong selection pressure among males to obtain those matings, resulting in the evolution of bigger body size and elaborate ornaments in order to increase their chances of mating.
    • This is an example of the extreme behaviors that arise from intense sexual selection pressure.

  • Natural Selection and Adaptive Evolution

    • Natural selection drives adaptive evolution by selecting for and increasing the occurrence of beneficial traits in a population.
    • Natural selection only acts on the population's heritable traits: selecting for beneficial alleles and, thus, increasing their frequency in the population, while selecting against deleterious alleles and, thereby, decreasing their frequency.
    • Natural selection does not act on individual alleles, however, but on entire organisms.
    • Natural selection acts at the level of the individual; it selects for individuals with greater contributions to the gene pool of the next generation, known as an organism's evolutionary fitness (or Darwinian fitness).
    • Through natural selection, a population of finches evolved into three separate species by adapting to several difference selection pressures.

  • Gas Vesicles

    • Because the gas vesicle is a hollow cylinder, it is liable to collapse when the surrounding pressure becomes too great.
    • Natural selection has fine-tuned the structure of the gas vesicle to maximize its resistance to buckling by including an external strengthening protein, GvpC, rather like the green thread in a braided hosepipe.
    • There is a simple relationship between the diameter of the gas vesicle and pressure at which it will collapse - the wider the gas vesicle the weaker it becomes.
    • Deep lakes that experience winter mixing will expose the cells to the hydrostatic pressure generated by the full water column.
    • This will select for species with narrower, stronger gas vesicles.

  • Time Pressure as a Barrier to Decision Making

    • All decisions are time-bound in the sense that we do not have an infinite amount of time to make a selection.
    • Still, firm and proximate deadlines and limited resources are common causes of time pressure.
    • There are some effective approaches to dealing with time pressure.
    • There is evidence that suggests the perception of time pressure may impact decision quality.
    • Explain the way in which time pressure can influence decision making

  • Implement the Course

    • After all of the alternatives have been analyzed and one has been selected, it is time to implement the decision.
    • A few of these pressures include coercive pressures and normative pressures.
    • Coercive pressures come from the social sanctions that can be applied if one does not act in socially legitimate ways.
    • Normative pressures arise from broad social values, and they concern what people think they should do.
    • Describe the three central steps to effectively implementing a decision upon the selection of a particular perspective or course

  • Avogadro's Law: Volume and Amount

    • Avogadro's Law states that at the same temperature and pressure, equal volumes of different gases contain an equal number of particles.
    • For example, 1.00 L of N2 gas and 1.00 L of Cl2 gas contain the same number of molecules at Standard Temperature and Pressure (STP).
    • As an example, equal volumes of molecular hydrogen and nitrogen contain the same number of molecules and observe ideal gas behavior when they are at the same temperature and pressure.
    • The model contains gas molecules under constant pressure.
    • Run the model and select different numbers of molecules from the drop-down menu.

  • Interpreting Phase Diagrams

    • Phase diagrams illustrate the effects selected variables of a system have on the state of matter.
    • Phase diagrams illustrate the effects selected variables of a system have on the state of matter.
    • Phase diagrams are divided into three single phase regions that cover the pressure-temperature space over which the matter being evaluated exists: liquid, gaseous, and solid states.
    • General observations from the diagram reveal that certain conditions of temperature and pressure favor certain phases of matter.
    • This is due to the solid phase having a higher density than the liquid, so that increasing the pressure increases the melting temperature.

  • Osmotic Pressure

    • Osmotic pressure is the pressure which must be applied to a solution to prevent the inward flow of water across a semipermeable membrane.
    • Osmotic pressure is the pressure which needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane.
    • It is also defined as the minimum pressure needed to nullify osmosis.The phenomenon of osmotic pressure arises from the tendency of a pure solvent to move through a semi-permeable membrane and into a solution containing a solute to which the membrane is impermeable.
    • This process is of vital importance in biology as the cell's membrane is selective toward many of the solutes found in living organisms.
    • Removal of water and addition of salt to meat creates a solute-rich environment where osmotic pressure draws water out of microorganisms, thereby retarding their growth.

  • Gauge Pressure and Atmospheric Pressure

    • Pressure is often measured as gauge pressure, which is defined as the absolute pressure minus the atmospheric pressure.
    • Gauge pressure is a relative pressure measurement which measures pressure relative to atmospheric pressure and is defined as the absolute pressure minus the atmospheric pressure.
    • Most pressure measuring equipment give the pressure of a system in terms of gauge pressure as opposed to absolute pressure.
    • For example, tire pressure and blood pressure are gauge pressures by convention, while atmospheric pressures, deep vacuum pressures, and altimeter pressures must be absolute.
    • Explain the relationship among absolute pressure, gauge pressure, and atmospheric pressure