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Related Concept Videos

Types of Selection01:46

Types of Selection

Natural selection influences the frequencies of particular alleles and phenotypes within populations in several different ways. Primarily, natural selection can be directional, stabilizing, or disruptive. Directional selection favors one extreme trait and shifts the population towards that phenotype while selecting against individuals displaying alternate traits. Stabilizing selection favors an intermediate trait with a narrow range of variation. Deviation from the optimal phenotype towards an...
Frequency-dependent Selection01:21

Frequency-dependent Selection

When the fitness of a trait is influenced by how common it is (i.e., its frequency) relative to different traits within a population, this is referred to as frequency-dependent selection. Frequency-dependent selection may occur between species or within a single species. This type of selection can either be positive—with more common phenotypes having higher fitness—or negative, with rarer phenotypes conferring increased fitness.Positive Frequency-Dependent SelectionIn positive...
Limits to Natural Selection01:38

Limits to Natural Selection

Organisms that are well-adapted to their environment are more likely to survive and reproduce. However, natural selection does not lead to perfectly adapted organisms. Several factors constrain natural selection.For one, natural selection can only act upon existing genetic variation. Hypothetically, redtusks may enhance elephant survival by deterring ivory-seeking poachers. However, if there are no gene variants—or alleles—for redtusks, natural selection cannot increase the prevalence of...
What is Natural Selection?01:32

What is Natural Selection?

Natural selection is an evolutionary process in which individuals with survival-promoting traits reproduce at higher rates. These favorable traits become more common within a population or species. Naturally selected traits initially arise via random genetic mutations. In order for selection to occur, there must be variation within a population, the trait controlling the variation must be heritable, and there must be an evolutionary advantage for variation in the trait.The Theory of Natural...
Relaxation of Skeletal Muscles01:29

Relaxation of Skeletal Muscles

The period of muscle contraction primarily influences the duration of stimulation at the neuromuscular junction (NMJ), the presence of free calcium ions in the sarcoplasm, and the availability of energy or ATP to support contractions.
When an action potential reaches the axon terminal, it depolarizes the membrane and opens voltage-gated sodium channels. Sodium ions enter the cell, further depolarizing the presynaptic membrane. This depolarization causes voltage-gated calcium channels to open.
Natural Selection and Mating Preferences01:06

Natural Selection and Mating Preferences

The principle of natural selection posits that organisms better adapted to their environment are more likely to survive and reproduce. This principle is closely intertwined with mating preferences, a key aspect of sexual selection, which evolutionary psychologists believe is driven by instincts to propagate one's genes. Such instincts significantly influence mating behaviors and preferences between genders.
Females, due to their biological roles in conception, pregnancy, and nursing, inherently...

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Relaxed selection in the wild.

David C Lahti1, Norman A Johnson, Beverly C Ajie

  • 1Department of Biology, University of Massachusetts, Amherst, MA 01003, USA. lahti@bio.umass.edu

Trends in Ecology & Evolution
|June 9, 2009
PubMed
Summary
This summary is machine-generated.

Relaxed selection, where environmental pressures on traits decrease, can lead to rapid trait loss. Understanding this process offers insights into evolution and applied issues like antibiotic resistance.

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Area of Science:

  • Evolutionary Biology
  • Ecology
  • Genetics

Background:

  • Natural populations often face reduced or absent selective pressures on traits.
  • This phenomenon, termed 'relaxed selection,' can significantly impact trait maintenance and evolution.
  • Previous studies have explored various ecological contexts of relaxed selection.

Purpose of the Study:

  • To review and synthesize recent research on the effects of relaxed selection on traits.
  • To provide a framework for understanding trait reduction and loss under relaxed selection.
  • To examine the implications of relaxed selection for applied ecological and medical issues.

Main Methods:

  • Literature review of recent studies on relaxed selection.
  • Analysis of genetic, developmental, and ecological factors in trait evolution under relaxed selection.
  • Synthesis of findings to establish a conceptual framework.

Main Results:

  • In specific systems like stickleback armor loss, the genetic and ecological underpinnings of trait evolution under relaxed selection are being elucidated.
  • Relaxed selection can drive rapid reduction or loss of traits.
  • The rate and extent of trait loss vary depending on the specific trait and ecological context.

Conclusions:

  • Relaxed selection is a significant evolutionary force with predictable outcomes for trait evolution.
  • Understanding relaxed selection provides insights into trait loss dynamics in natural populations.
  • This framework is applicable to critical issues such as antibiotic resistance and invasive species success.