1. NATURAL SELECTION ***READ 8.1***
What was happening in the video? What kind of selection is this?
***READ 8.1***

2. Types of Selection
Directional Selection: when selection favour individuals with a more extreme variation of a trait; selection that favours an increase or decrease in the value of a trait from the current population average.

3. Types of Selection Stabilizing Selection: occurs when the average
phenotype within a population is favoured by the
environment; selection against individuals exhibiting
traits that deviate from the current population
average.
This is human birth weights
Birth weights are variable because it is heritable
According to natural selection, babies born at weights offering the best chance of survival should be more numerous
Around 6-7 lbs are where mortality rates are the lowest and most babies survive
Less than 6lbs are premature and heavier babies often experience birth-related complications

4. Types of Selection

5. Types of Selection
Disruptive Selection: selection that favours two or more variations of a trait that differ from the current population average; favours individuals with variations at opposite extremes of a trait over individuals with intermediate variations.

6. Types of Selection

7. Types of Selection
Sexual Selection: differential reproductive success caused by variation in the ability to obtain mates; results in sexual dimorphism, and mating and courtship behaviours.
Ask them what they think is attractive and what they do to impress girls (cars, money, athletic, smart)
Might be a dance
In this society what is beautiful?
Talk about in the philippines, ask about where their from, or their certain culture

8. Types of Selection (Sexual)
Favours any trait that enhances the mating success of an individual
Ie. Evolving appearances and behaviours that are quite different in males and females
Ex. Male-male competition
These traits might be a disadvantage when it comes to predators (bright colours, distinctive song)
Also with plants: attract pollinators

9. Altruism
At times, animals behave in ways that reduce their individual fitness and increase the fitness of others
“helping others”
There are two types of Altruism:
Kin Selection
Group Selection
Talk about how I don’t want to raise kids but how I love and babysit cousins and nephews and nieces sometimes

10. Kin Selection
Helping relatives to survive and reproduce even if it means forgoing breeding yourself
You share 50% of your genes with each parents and 50% with a sibling
If an individual forgoes breeding and instead helps raise a close relative, it is helping pass on a portion of its own genes to the next generation
The more closely related an individual is to another, the more likely it is to forego a breeding attempt

12. Group Selection “for the good of the group”
In social populations, small groups will compete with other small groups for resources
Any adaptation that would improve a group’s survival over another group would also improve the individuals survival even if it doesn’t directly benefit the individual
By cooperating with each other they ensure each other’s survival

14. Himalayans = 40% oxygen level compared to sea level
When people from the lowlands are up in the mountains, red blood cell count increases but makes the blood more viscous
Places stress on the heart = reduced fertility = increased child mortality
Tibetans who live at high altitudes don’t have an elevated red blood cell count but don’t have difficulty coping with loe oxygen levels
Genetic mutations = increase oxygen carrying capacity of their blood while maintaining normal red blood cell counts
MICE: chose only those individuals who ran the most on the wheel
10 generations later, mice exhibited much higher running distances and average speeds compared to control populations
What is this an example of that we already learned about? Artificial selection, selective breeding

16. Evolutionary Change without Selection
Genetic Drift:
changes to allele frequency as a result of chance; such changes are much more pronounced in small populations
Random shifting of the genetic makeup of the next generation
When individuals produce offspring, the chances of passing on a particular allele is subject to random chance
In small populations
Can result in a particular allele can be very common or disappear entirely
When it disappears, it reduces genetic diversity
Ask class what they think of when i say “bottleneck effect”, and founder effect

17. 1. BOTTLENECK EFFECT
Bottleneck: a dramatic, often temporary reduction in population size, usually resulting in significant genetic drift
Loss in genetic diversity after an extreme reduction in population size
Can have adverse
consequences
Seals, cheetah (7) - don’t know what happened but years ago there was estimated to be only 7 of them left
Low reproductive success and high juvenile mortality rates
Northern elephant seal – 20 of them in the 1890s because of overhunting

18. 2. FOUNDER EFFECT
Founder effect: genetic drift that results when a small number of individuals separate from their original population and establish a new population
Initial population would have a different mix of alleles, by chance alone
Populations from bottleneck and founder effects are subject to the effects genetic drift
Further increases the chances that their gene pool will differ from the original population

19. Big Horn Sheep
1975: 20 sheep
1999: ~650 sheep

20. HARDY-WEINBERG PRINCIPLE
The Hardy-Weinberg Principle: in large populations in which only random chance is at work, allele frequencies are expected to remain constant from generation to generation
Any factor that causes allele frequencies to chance leads to evolutionary change
Two mathematicians, Godfrey Hardy and Wilhelm Weinberg, used mathematical reasoning to explain the relationships between allele frequencies within a population and the chances those frequencies will remain constant (explain, don’t put into note)

21. HARDY-WEINBERG PRINCIPLE
These conditions lead to evolution
Natural selection: favours the passing of some alleles over others
Small population size: increases the likelihood of genetic drift
Mutation: introduced new alleles to a population
Immigration/emigration: introduces or removes alleles in a population
Horizontal gene transfer: the gaining of new alleles from a different species