What Are the Three Basic Phases of Smiling? at What

question 55

Short Answer

What are the three basic phases of smiling? At what ages do these phases begin? When does laughing usually begin?

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Definitions:

Derived Trait

A character that is present in a clade under consideration, but not in any of the clade’s ancestors.

Stabilizing Selection

A type of natural selection that favors intermediate variants by acting against extreme phenotypes, leading to a decrease in a population's genetic variance.

Clutch Size

The number of eggs laid or offspring produced by an animal, particularly birds, at one time or during one breeding session.

Directional Selection

is a type of natural selection that favors one extreme phenotype over others, causing a shift in allele frequency over time.