Lecture 3:Processes of Evolution

Question 1

What are 3 common misconceptions about Natural Selection

Answer 1

1. Natural selection does NOT change individuals, rather populations
2. Evolution is NOT progressive and NOT goal directed; The best competitor wins
3. Adaptation is NOT perfect and is always limited by genetic material

Question 2

Directional selection

Does genetic variation increase/decrease, biston betularia?

Answer 2

• Occurs when there is a** change of frequency** that proceeds in one direction over time
• Reduces genetic variation
• Example: Biston betularia in urban areas after the Industrial Revolution because the proportion of melanic form increased in the population during this time

Question 3

Cliff Swallows

How do they show directional selection?

What is something cool they do?

Answer 3

Birds that build nests on a cliff
- During a cold winter, only the large cliff swallows had survived while the others had starved
-

Swallows can “cheat” by putting their own eggs in other swallows’ nests so they can use their energy making more children

Question 4

Stabilizing selection

Genetic variation?

Answer 4

Type of selection that favors intermediate individuals in the population and weed out the extreme
-Reduces genetic variation

Question 5

What type of selection tends to keep populations the same for a particular trait for a period of time?

Answer 5

Stabilizing selection as it is known as “hidden” natural selection

Question 6

Disruptive selection

Variation?

Answer 6

Inidivuals at both extremes of a range of phenotypes are favored
- Increases the amount of variation in a trait

Question 7

During disruptive selection, what happens when the species become completely distinct?

Answer 7

This could lead to two different species

Question 8

Sexual selection

When does it occur? What is the result of a more attractive partner?

Answer 8

A consequeunce of competition for mates
- It occurs when there are differences in the ability to attract mates
- “More attractive” partners mate successfully, reproduce more and are more evolutionary fit

Question 9

What causes sexual selection?

Answer 9

Females have greater reproductive costs during development of the egg or during parental investment; the cost of reproduction is lower for males
THEREFORE
Females must choose a good mate so her offspring is successful

Question 10

What is the “fundamental assymetry of sex”?

Answer 10

The difference in investment for reproduction between sexes

Question 11

Intersexual Competition/Intrasexual Competition

Answer 11

Intersexual Competition- female choice; females choose the “best” male in their eyes AKA “mate choice”
Intrasexual Competition-Males compete for territory and access to females

Question 12

What are some things that can influence female choice?

Answer 12

1. Peacock color on their feathers
2. Artificial cues: Experiment showed female zebra finches prefer a red colored ring over a green colored rings in males
3. Nuptial gifts: Males can provide resources that females can use for themselves or their young

Question 13

What are some traits that have evolved due to male-male competition?

Answer 13

1. antlers on male deer can be used during battle
2. elephant seals (Their large size) can be used during fighting
3. In fruit flies, males can compete with each others sperm and have developed strategies to be the sperm-owner

Question 14

1. Sexual selection has the capacity to evolve non** (blank)** traits
2. One of the consquences of sexual selection is sexual (blank)
3. Sexual selection tends to act on the less **(blank) **gender

Answer 14

1. adapative
2. dimorphism
3. choosy

Question 15

How is birth weight an example of stabilizing selection?

Answer 15

Birthweight is a type of stabilizing seleciton is lighter babies and heavier babies often have higher mortality rates whereas the babies with an intermediate weight had lower mortality rates

Question 16

What type of selection is the gill raker fish?

Answer 16

Diruptive Selection: Type of fish that has filters. Dense gills are good for capturing small things like plankton whereas less dense gills are good for capturing small animals without getting clogged in mud (Ones in between are not good at either). The two extremes are the best competitors.