Types of Selection Flashcards
3 Types of selection
Directional selection
Stabilizing selection
Disruptive selection
Directional Selection
Directional Selection- occurs when selection favours individuals with a more ___extreme__________________________ of a trait.
The result is a shift away from the ____average________________ condition.
Occurs when an organism must adapt to changing conditions.
Very common in ___artificial breeding_____________________________, where individuals with an enhanced trait are selected.
Stabilizing Selection
occurs when the ___average phenotype________________________ within a population is favoured by the environment.
The selection changes the population so that the ___extremes_____________are eliminated.
Most __common _____________ form of selection.
Disruptive Selection
favours individuals with variations at __opposite extremes____________________of a trait over individuals with intermediate variations.
The population is basically divided into _two_____ individual groups of extreme traits.
Sexual Selection
is the favouring of any trait that specifically enhances the _____matin success of an individual___________________ of an individual.
Often leads to males and females of a species evolving appearances and behaviours that are quite different from each other. (Sexual Dimorphism)
Female Mate Choice
In many species, females choose mates based on physical traits, such as bright ______coloration_________ or behaviours.
Traits like bright coloration and large antlers can be favoured by sexual selection but can often be a ___disadvantage______________________ to longevity of life. It makes avoiding predators more difficult.
Male-versus-Male Competition
Males often fight each other to establish ___control____________ over a territory that is home to females with which they can mate.
Winning can ensure reproductive success as they can often ___mate________ with dozens of females each year.
The genes of the shorter lived but ___dominant___________ male are destined to become more common.
3 types of Evolutionary Change without Selection
Genetic Drift
Bottleneck
Founder Effect
Genetic Drift
the random shifting of the genetic makeup of the next generation. Changes are much more pronounced in ___small populations
Genetic Bottlenecks
result in a loss in ___genetic dviersity________________________following an extreme reduction in the size of a population
Founder Effect
occurs when a ________small number_________________ of individuals establish a new population.
The initial population would have a different mix of alleles than the large mainland population. An allele that was common in the large population might be uncommon in the founding population. Or, a rare allele might be much more common in the new population.
Consequences of Human Influence
Humans interact with all other species, either directly or indirectly. These interactions act as agents of natural selection and have the potential to influence the evolution of species.
