Topic 1 Evolution: Natural Selection

Question 1

• Natural selection is responsible for producing adaptations, which are superior inherited traits, that increase an individual’s fitness. Fitness is the ability to survive and produce fertile offspring. If lots of offspring are produced but they die, then it’s not good fitness.

Answer 1

Note

Question 2

1. Populations possess an enormous reproductive potential if all offspring produced also survived.
2. Population size remains stable and it generally fluctuates around a constant size.
3. Resources are limited and do not increase as the population grows larger.
4. Individuals compete for survival because a growing population will exceed the available resources.
5. There is variation among individuals in a population such as skin color.
6. Much of the variation is heritable through passing down DNA.
7. Only the most fit individuals survive, otherwise known as survival of the fittest.
8. Evolution occurs as favorable traits accumulate in the population because the best adapted individuals leave more offspring.

Answer 2

Key Points

Question 3

• Individuals cannot evolve, only populations can

Answer 3

Note

Question 4

• The bell curve favors an intermediate, like how the average height in humans is in the middle.

Answer 4

Stabilizing Selection

Question 5

• The favoring of traits that is at one extreme of the range. Traits at opposite extremes are selected against.

Answer 5

Directional Selection

Question 6

• The selection of dark- colored, melanic, varieties in various species of moths, like the peppered moth, as a result of industrial pollution. This is a specific type of directional selection.

Answer 6

Industrial Selection

Question 7

• This selection occurs when the environment favors extreme or unusual traits while selecting against common traits. For example, a certain environment may favor short and tall heights while the average height is selected against.

Answer 7

Disruptive Selection

Question 8

• The differential mating of males or females in a population

Answer 8

Sexual Selection

Question 9

1. Intersexual Selection
2. Intrasexual Selection
3. Sexual Dimorphism

Answer 9

Types of Sexual Selection

Question 10

• Females choose superior males, which increases the fitness of the offspring. Because females invest more energy into their offspring, they want to maximize the quality of their offspring by picking fit males.

Answer 10

1. Intersexual Selection

Question 11

• When males compete and fight with other males for better mating opportunities. Males increase fitness of offspring by maximizing quantity. Intrasexual selection favors traits like musculature, horns, large stature, etc.

Answer 11

2. Intrasexual Selection

Question 12

• The differences in appearance of males and females, which is a form of disruptive selection. This occurs because female choice leads to traits and behaviors in males that are favorable to females. Male traits like colorful plumage or elaborate mating behavior will be selected for by females.

Answer 12

3. Sexual Dimorphism

Question 13

• This is a form of directional selection carried out by humans when they breed favorable traits, and is not natural selection.

Answer 13

Artificial Selection