Natural Selection

Question 1

Natural Selection

Answer 1

• Evolution occurs when natural selection acts on the genetic variability of a population
• environment favours certain trait over another
  higher rates of Sickle-Cell Anemia in countries where Malaria is common

Question 2

Types of natural selection

Answer 2

• directional
• satblizing
• disruptive

Question 3

Directional Selection

Answer 3

• selection favours individuals with a more diff variation of a trait
• very common in breeding

Question 4

Directional Selection example

Answer 4

• long girrafe necks being favoured over short

Question 5

Stabilizing Selection

Answer 5

• average phenotype within a population is favoured

Question 6

Stabilizing Selection example

Answer 6

• hummingbirds medium sized beaks are favoured
• long beaks disadvantage because it requires too much energy to carry around
• The short beak is a disadvantage because it cannot reach the food within the flower effectively

Question 7

Disruptive Selection

Answer 7

• favours individuals with variation at opposite extremes of a trait over individuals with average variations

Question 8

Disruptive Selection example

Answer 8

• if you are a flower which hummingbirds feed upon, a medium sized flower would be a disadvantage
• Large flowers are favoured because the beak is too small to get into the flower well
• Small flowers are also favoured because the beak would be too large to get into the flower well

Question 9

Sexual Selection

Answer 9

• favours a specific trait because it enhances the mating success of an individual
• some traits may help with fitness (reprodutve success)
• if resources are plentiful, there will be sexual selection

Question 10

What does sexual selection cause

Answer 10

• leads to males or females within a population evolving appearances or behaviors which are quite different from each other
• causes female mate choice or male-versus-male competition

Question 11

Change Without Selection

Answer 11

• genetic drift
• bottleneck
• the founder effect

Question 12

Genetic drift

Answer 12

• Random chance
• When individuals produce offspring, any particular allele is passed on by chance
• The smaller the number of individuals in a population, the greater the impact of random chance
• changes geens iwthout selection pressure

Question 13

Bottleneck

Answer 13

• loss in genetic diversity following an extreme reduction in the size of a population
• Based on which individuals survive the population reduction, there may be a huge change in allele frequency

Question 14

Founder effect

Answer 14

• small # of indiduals move to new location, and whoever moved are the ppl making up new population
• may be a huge change in allele frequency dependent on which individuals establish the new population