Theme 4C (Part 1, Ways of Change) Flashcards
(36 cards)
1
Q
Genetic Drift
A
- Random Processes - Can affect the f of genetic variants and traits during life cycle, especially mating & survival
- Evolution by random change
- Random if probability of occurence isn’t affect by individuals phenotype
- Change in allele f due to chance in finite populations, especially small ones
2
Q
Effect of Genetic Drift
A
- Evolution in finite populations
- Random sampling error, error higher in smaller pop
- Jelly Bean / M&M example
3
Q
Fixation
A
- Stable, permanent in reference to an alleles presence
4
Q
Bottleneck
Genetic drift reduces genetic variation in a pop
A
- Temporary reduction in pop size cause drift, reduce genetic variation, & cause genetic difs b/w pops - significant conservation implications
5
Q
Founder Effect
Genetic drift reduces genetic variation in a pop
A
- Small founding pop, less diversity results in following gens
6
Q
Phylogeny
A
- Human pops closely related to neighbours
7
Q
Founder events in Human History
A
- Based off of path out of Africa, more heterozygosity (genetic diversity) in African individuals
- Least in Americas
- All non-Africans descend from a small pop of humans who lived in Ethiopia
8
Q
Population Divergence
A
- Pop who over time changes distribution to homozygous on opposite ends
- Over long period of time, allele fixation occurs and populations diverge as they are now distinct from one another
9
Q
Non-random Mating
A
- Mating individuals are more closely related or less closely related than those drawn by chance from a random mating pop
- 3 types
10
Q
Interbreeding
A
- Mating with Relatives (Mating system)
- Caused by small pops
- Doesn’t alter allele f by itself
Ex. Self crosses with plants that can have male + female gametes
11
Q
Outbreeding
A
Mating with individuals more distantly related (non-relative)
12
Q
Assortative mating
A
- Individuals with similar genotypes and/or phenotypes mate with one another more frequently than would be expected under random mating pattern
- Blue frogs mostly mating with other blue frogs and not red
13
Q
Inbreeding Depression
A
- Rare deleterious alleles more likely to combine in homozygotes
- More offspring with poorer fitness
I.e. Cystic fibrosis carriers inbreeding, making it more likely
Often in bottleneck or founder pops
14
Q
Natural Selection
A
- Predictable change in f distribution of a trait b/w the parental & offspring gens at a result of 3 conditions
- Individuals vary
- Survival and reproduction not random
- Inheritance
Galapagos finches, big seeds vs small seed beaks
15
Q
Three patterns of natural selection
Directional Selection
A
- Individuals of one extreme phenotype favoured
- Evolution of the trait mean occurs when fitness varies +’vely or -‘vely with “trait” size
Peppered moth
16
Q
Three patterns of natural selection
Stabilizing Selection
A
- Individuals with intermediate phenotype favoured
- Extreme phenotype selected against
- Trait mean doesn’t change
17
Q
Three patterns of natural selection
Disruptive Selection
A
- Both extreme phenotypes favoured; intermediate phenotype selected against
18
Q
Modes of Selection
No selection
A
- When survival and reproduction are not random
19
Q
Viability Selection
A
- Differences in survival
20
Q
Fecundity Selection
A
- Differences in reproductive success
21
Q
What defines male vs. female
A
- Gametes!
- Male produce abundant, smaller, energetically cheap, motile sperm
- Female produce few, larger gamete, energetically expensive, less motile eggs
Parental investment dif, men less than female
Parental care dif, cost of bearing (pregnancy) & raising offspring typically greater in female
22
Q
Sexual Selection
A
- Purely success in having offspring
- Result of heritable difs in fertility &/or survival
- Darwin viewed as dif than nat sel, now we don’t
Moose antlers getting caught in trees, but fight other male for mates
23
Q
Reproductive Success
A
- Females limited by resources
- Males limited by access to females (usually)
- Is = to fecundity + mating success
24
Q
Sexual Monomorphism/Dimorphism
A
- Mono - Male and female look the same
- Di - Visual dif b/w male and female
25
# Aspects of Sexual Selection
Intrasexual selection
* Fitness dif resulting from dif abilities of members of the same sex to compete (male-male competition, ape teeth/jaw)
26
# Aspects of Sexual Selection
Intersexual selection
* Fitness dif resulting from preferential mating b/w specific males & females (mate choice, peacock with cooler colours competition)
27
Allopatric Speciation
* Geographically Isolated
* Physical barrier divides geographic range
* Gene flow ceases & separate pops evolve independently
* Over time, dif alleles become fixed, because of mutation + drift &/or selection
| 2 - vicariance event
## Footnote
Can also be a dispersal with half of pop, or a small pop leaves and small pop subject to drift forces
28
Confirm Allopatric Speciation
* Provided sufficient time has elapsed for divergence
* Barrier removed and pops go back in contact, stay distinct
* Interbreeding prevented via pre/postzygotic mechanism
29
Sympatric Speciation
* Pop in same geohraphic location
* Disruptive selection makes two distinct sub pops
* Sub pops diverge into 2 dif species
* Stages - Initial: Polymorphism that affects fitness. Then: Mating b/w 2 forms discourage (prezygotic) and or disadvantageous (postzygotic)
30
Polyploidization
* Can cause sudden speciation
* Meiosis fails & organism produces 2n gametes
31
# Polyploidization
Autopolyploids
* Can only mate with another autopolyploid = reproductive isolation
* Caused if 2n gamete fertilized with another 2n gamete
32
# Polyploidization
Allopolyploidization
* Similary to autopolyploid but involves first the mating b/w 2 closely-related species
33
Species Concepts
* Framework to address how to organize the discrete clusters of variation in nature
* Dif concepts place dif emphasis on dif factors
* 2 major categories
34
# Species Concepts
Morphological
* Individuals look alike
* Most traditional concept
* Advantage: Practical, simple to use
* Disadvantage: No clear genetic or evo justification; choice of characters may be arbitrary
35
# Species Concepts
Reproductive/Biological Species Concept (BSC)
* Ability to produce offspring
* Interbreeding natural pops
* Advantage: Clear criteria, clear evolutionary justification
* Disadvantage: Difficult to distinguish in the field - less of an issue with genomics
36
# Species Concepts
Others: Phylogenetic/evolutionary
* Shared evolutionary history
* Common ancestry
* More useful when thinking asexual species
