U3 Terms Flashcards
Recombination
Moves mutations around to different copies of a chromosome
Independent Assortment
Influences how chromosomes get packaged into gametes
Mutations are the…
and they… (3 things)
“Variation factory”
1) Occur randomly
2) Are found in everyone
3) Can be good, bad, or neutral
Production of new variation CANNOT… (2)
1) Be stopped
2) Be predicted
Natural Selection
Heritable variation being transmitted and sorted differently based on different environments
Components of Natural Selection (3)
1) Production (heritable variation)
2) Transmission (heredity)
3) Sorting (survival/reproduction)
Types of Selection
1) Stabilizing selection
2) Directional selection
3) Disruptive selection
Stabilizing Selection
(Bell curve gets skinnier: removing the variance at both extremes)
–> Variance decreases
–> Mean peak (most common phenotype) stays the same
Directional Selection
(Bell curve moves towards one side)
–> Mean value of the character (most common phenotype: the peak) changes
–> Causes the removal of one of the extremes (the one shifting away from)
Disruptive Selection
(Bell curve peak is disrupted)
–> Variance increases
–> Extremes increase
–> Medium variants become less common and the extremes become more common
Mutations are…
Random
Natural selection is…
NON-random
Sexual Dimorphism
The systematic difference in form between individuals of different sex within the same species
The environment does NOT ______ mutations
cause
Environmental change or the need to adapt CANNOT….
Change or force the variation factory to produce different/specific variation
Sexual Selection
Explains the patterns in which there is variation between the sexes in a single species
(Why different species have different types of sexual dimorphisms)
How resources are distributed has a major effect on….
Sexual Selection
Clustered Resources
Males can try to control access to resources that females require
–> Leads to more male-male competition
–> Males battle for control of resources and female mates (The “burlier” usually wins)
Dispersed Resources
Males CANNOT control access to resources (as they are spread out)
–> Males instead try to attract females
–> The fancier a male, the more attractive they can be to females (in most species)
Why do only males get “fancy” and females don’t?
Because having fancy traits are selected against by natural selection (less camouflage = less survival)
Males will get “fancier” and “fancier” until…
It begins to seriously affect their survival
Natural vs Sexual Selection
NATURAL = Leads to adaptations for gathering resources and surviving
SEXUAL = Leads to adaptions for gathering mates and breeding
Natural and sexual selection are composed of the same steps. In which step do they differ?
SAME = Production and Transmission steps
DIFFERENT = Sorting step
Random
Lack of pattern or predictability of an event
(No order of clear pattern)
CHANCE
Non-Random
Presence of a pattern or a predictable event
(There IS order and a pattern)
–> Opposite of chance
Genetic Drift
(Third sorting process)
Sorting (survival) of individuals/alleles due to CHANCE
–> Random sorting/survival
Genetic Drift is NOT:
The event causing the sorting (Ex: forest fire)
Genetic drift is more common in/for…
1) Smallepopulations
2) Rare alleles
Bottleneck Effect
A sharp reduction in size of population due to an environmental event
–> Reduces variation (as only certain variants survive the event)
Founder Effect
When a small group of migrants (not genetically representative of the population from which they came) establish in a new area
–> Reduces genetic variation in the newly established population
Random Components of Evolution
1) Mutation (variation factory)
2) Genetic Drift
Non-Random Components of Evolution
1) Natural Selection
2) Sexual Selection
Species
Groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other groups
Speciation
The evolution of populations to become distinct species
What causes speciation?
1) Groups becoming separated in space
2) Groups becoming different enough in form or behavior that individuals of one group do not regularly mate with individuals outside the group
For species to form…
populations must become different enough so they can’t reproduce
Reproductive Isolation
The prevention of different species producing offspring together
(2 main mechanisms)
Main mechanisms of reproductive isolation:
1) Pre-Zygotic Isolation
2) Post-Zygotic Isolation
Pre-Zygotic Isolation
Barrier that occurs BEFORE a zygote can be made
(3 main barriers)
Main Pre-Zygotic Isolating Factors:
1) Behavioral Isolation
(Ex: different bird songs)
2) Temporal Isolation
(Ex: mating in different seasons)
3) Habitat Isolation
(Ex: terrestrial vs aquatic frogs)
Post-Zygotic Isolation
Mating and fertilization actually occur producing a zygote BUT some barrier separates the species still
(3 main barriers)
Main Post-Zygotic Isolating Factors:
1) Infertile Offspring (Sterile)
(Ex: Zonkey)
2) Offspring are weak/sick
(Ex: Don’t survive very long)
3) Genetic Incompatibility = Lack of development (of embryo or beyond)
