Selection, Group Election & Kin Selection

Question 1

Stabilising selection

Answer 1

Majority are the average - this is the fittest and is under selection + the 2 extremes are less fit

• Those with avg. are fitter - reproduce more - over gens. the trait occurs more - extremes erodes as they don’t reproduce as much

Question 2

Example of Stabilising Selection - Birth Weight

Answer 2

• Low moratlity at avg of 7lbs
• If bigger mortality increases - issues being born
• Very small babies - likely to be premature + have complications

Question 3

Disruptive Selection

Answer 3

One end of the spectrum of a continuous trait is fittest

Question 4

Example of Disruptive Selection - Directional Effect of fishing

Answer 4

Natural selection favours larger fish.
- Big fish produce more eggs
- Fishing removes larger fish
- Favours smaller size at maturity and earlier maturation

Less big fish - more selection pressure for small fish that mature faster - become fitter

Question 5

Artificial Directional Selection

Answer 5

Bristle number in fruit flies
- Breed from those with high or low bristle number

=> When they breed only those on extreme in isolation - bristles number gets more extreme

Question 6

Group Selection

Answer 6

• Groups with lower extinction/higher speciation increase.
• Groups with a given adaptation go extinct at a lower rate
• Restraining food intake by group allows the group to survive
• Groups that don’t restrain go extinct

=> more likely to survive + split off and reproduce = pass on traits

Question 7

What needs to happen for group selection?

Answer 7

• Assessment of food availability
• Communication to others in group
• Restriction of reproduction

Group selection is not as strong as individual selection - since reproduction has to be withheld

Question 8

Asexual Reproduction Pros

Answer 8

• Is fitter + more efficient
  => population grows faster

Question 9

Disadvantage of Sexual Reproduction - Needs a partner

Answer 9

• Males are the 50% cost of sexual
  reproduction
• Number of individuals is halved as males must be produced to continue sexual reproduction

Question 10

Advantage of Sexual Reproduction - Genetic variation

Answer 10

• Heterozygous mutation is hidden - Two mutations can only be brought together by sexual
  => very rapidly causes genetic variation

Question 11

Red Queen Hypothesis - “It takes
all the running you can do to stay in the same place!”

Answer 11

Because of competition, environmental change, and predation - you have to evolve/ run as fast as possible to stay the same / stay in the same place

Question 12

Disadvantage of Asexual Reproduction - No Variation

Answer 12

With no sexual reproduction - change can only come about by random mutation to have a new advantageous trait

Question 13

Altruism - Helpers at the Nest

Answer 13

• Offspring from previous years help their parents instead of reproducing
• Number of young fledged goes down if helpers removed
• Helpers aid relatives more than strangers