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Types of Selection

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...

Mate Choice

Mate Choice

Mate choice—the decision about whom to mate with—is a type of natural selection, since animals must reproduce to pass down their genes. Mate choice is also called intersexual selection because the behavior occurs between the sexes.

What is Natural Selection?

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...

Optimal Foraging

Optimal Foraging

How animals obtain and eat their food is called foraging behavior. Foraging can include searching for plants and hunting for prey and depends on the species and environment.

Frequency-dependent Selection

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...

Ecological Niches

Ecological Niches

All organisms have a position within an ecosystem. The complete set of living and nonliving factors—including food resources, climate, and terrain—that define the position of a given organism are collectively referred to as the organism’s ecological niche.Multiple species cannot occupy the exact same niche within their habitat. If the niches of two or more species overlap to a large extent, the competitive exclusion principle dictates that one species will outcompete the other, forcing it to...

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Related Experiment Video

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Denaturing Gradient Gel Electrophoresis (DGGE)

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Published on: February 25, 2007

Editor's pick.

M S Wilkes, M Shuchman

The Western Journal of Medicine

|August 30, 2008

Summary

This summary is machine-generated.

In 1994, US Congress reduced the Food and Drug Administration's (FDA) regulatory power over dietary supplements and herbs. This deregulation aimed to support industry growth and consumer demand for alternative health products.

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BioMEMS and Cellular Biology: Perspectives and Applications

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Published on: October 1, 2007

Area of Science:

Public Health Policy
Regulatory Science
Herbal Medicine

Background:

In 1994, US legislation significantly limited the Food and Drug Administration's (FDA) authority over the regulation of herbs and dietary supplements.
This legislative change was influenced by both industry manufacturers seeking deregulation for economic growth and a growing consumer base for alternative health products.

Purpose of the Study:

To analyze the impact of the 1994 US law on the regulation of alternative health products.
To examine the factors driving the deregulation of dietary supplements and herbal products.

Main Methods:

Legislative analysis of the 1994 US law impacting FDA powers.
Economic analysis of the dietary supplement and herbal product industry's growth post-1994.
Examination of consumer trends and demand for alternative health products.

Main Results:

The law led to a significant curtailment of FDA regulatory powers concerning herbs and dietary supplements.
The economic value of the alternative health products industry has tripled since the law's enactment.
Consumer demand and usage of these products represent a substantial market force.

Conclusions:

The 1994 legislation reflects a balance between industry interests, consumer preferences, and regulatory oversight.
The deregulation has fostered significant economic growth within the alternative health products sector.
Understanding consumer engagement with alternative products is crucial for public health policy.