Types of Natural SelectionExamples include climate, food availability, andpredators.
Types of Natural SelectionThere are 4 types of Natural Selection:1) Directional Selection2) Stabilizing Selection3) Disruptive Selection4) Sexual Selection
Types of Natural SelectionSuppose a certain mouse population has a rangeof fur colours, from light brown to dark brown.
Directional Selection1) Directional selection occurs when a selectivepressure favours an extreme variation of a trait.
Directional SelectionFor example, the surrounding woody environment mayprovide better camouflage for darker mice, thus mostof the lighter colour mice may be easily hunted.
Stabilizing Selection2) Stabilizing selection occurs when a selectivepressure favours the average phenotype.
Stabilizing SelectionFor example, a new predator may only be able to seevivid colours (like white and dark brown), allowing thedull brown mouse to avoid detection and escape.
Disruptive Selection3) Disruptive selection favours extreme traits forsurvival while the average phenotype declines.
Disruptive SelectionFor example, predators may not eat the vividlycoloured mice in the area because the other white anddark brown creatures in the area are toxic.
Sexual Selection4) Sexual selection favours traits that increase thesuccess for an organism to find a mate and reproduce.
Sexual SelectionUsually involves (female) mate choice or (male versusmale) competition.Examples:PeacockSatyr tragopan (video)Bighorn rams (video)
Sexual Selection Sexual Dimorphism is the difference of phenotypes between males and females of the same species. These are the traits often used in sexual selection.Examples include:- Colour- Height- Size of a particular feature(such as horns or tusks)
Sexual SelectionThe satyr tragopan displays its blue horns and wattleto attract females.