Lecture 14

Question 1

What is altruistic behaviour and give an example

Answer 1

• self-sacrificing behaviour
• helping others at personal cost

ex.
- birds feeding or protecting offspring from another nest
- warning calls in birds or mammals to alert others of a predator approaching
- helping to attack and “mob” a predator to drive it away

Question 2

How can you explain the existence of altruistic behaviours in some animals?

Answer 2

• most cases in animal studies determine that altruism usually happens in support of CLOSE GENETIC RELATIVES (also known as “kin”)

Question 3

What is inclusive fitness?

Answer 3

• direct fitness + infirect fitness

WILLIAM HAMILTON redefined fitness based on both components

Question 4

What is the concept of “Kin selection”

Answer 4

• selection arising from the indirect benefits of helping relatives raise offspring, rather than reproducing yourself is often the result of altruistic behaviour

Question 5

What is the Hamilton RUle

Answer 5

• an altruistic allele can increase in frequency when: relatedness*benefit is greater than the cost
• rB > C
  where:
  r = the coefficient of relatedness
  B = the benefit to the recipient
  C = the cost to the altruist

Question 5

Review the coefficient of relatedness

Answer 5

• fraction of genes shared

r = 0.5 with offsprings and full siblings
r = 0.25 with grandchildren and half siblings, nephews and nieces
r = 0.125 with great-grandchildren and cousins

• identical twins are close to 1.0 (100%) genomically the same, but will change over time due to mutations, and other genetic (epigenetic) and environmental factors

Question 5

Why is the frequency of alarm calling the highest in females of reproductive age?

Answer 5

• the males migrate to other areas when they mature
• the females stay close to the area of the offsprings therefore they protect them with the alarm callings

that is why many “neighbours” are their own offspring and other close genetic relatives (kin)

Question 6

Do black-tailed prairie dogs prefer to help relatives when they give an alarm call? - answer the conclusion of the experiment

Answer 6

Hypothesis: individuals give an alarm call only when close relatives are near

Null Hypothesis: the presence of relatives has no influence on the probability of alarm calling

Experimental setup:
1. Determine relationships among individuals in prairie dog coterie
2. Drag stuffed badger across territory of coterie
3. From observation tower, record which members of coterie give an alarm call
4. Repeat experiment 698 times. Each prairie dog coterie is tested 6-9 times over a 3-year period

Prediction of Kin-selection Hypothesis : indivudlas in coteries that contain a close genetic relative are more likely to give an alarm call than individuals in coteries that do not contain a close genetic relative

Prediction of null hypothesis: the presence of relatives in coteries will not influence the probability of alarm calling

Conclusion: Alarm calling usually benefits relatives. More callings with relatives or offsprings around

Question 7

What does the Hamilton’s rule do and does not do?

Answer 7

• does NOT help animals make decisions consciously
• DOES provide a model for understanding how genes that contribute to altruism can increase through kin selection

Question 8

Define fitness

Answer 8

• an individual’s contribution of genes to the next generation, relative to other individuals in the population

Question 9

What are the direct and indirect ways an individual can maximize his or her own fitness?

Answer 9

Directly
- by contributing to the survival and reproductive success of one’s own offspring

Indirectly
- by contributing to the survival and reproductive success of close relatives or kin with shared genes

NOTE: fitness is relative. An individual or group’s fitness is always compared with other individuals or groups

Question 10

Give an example of inclusive fitness

Answer 10

two male turkeys displaying together to attract femals. Even if only 1 brother (r=0.5) mates, the non-mating male still gets a genetic benefit in the next population from genes shared with brother’s offspring (nephews and nieves) : each with r=0.25

Question 11

review the florida scrub jays defending their nest (helper research)

Answer 11

Florida scrub jays defending their nest (which contains four young hidden under the mother). The father is crouched on top of the mother. Their helper is two-year-old bachelor at the right. Most helpers are prior offspring of the mated couple, but this one is a brother of the breeding male.

Question 12

What is genetic drift?

Answer 12

• genetic drift is a change in allele frequencies due to CHANCE events (random sampling errors)

ex. changes in allele frequency that are random and are not the result of fitness advantages/disadvantages

Question 13

does genetic drift affect small or large populations more

Answer 13

• the effects of genetic drift are strongest in very small populations

Question 14

Does genetic drift reduce or increase genetic diversity

Answer 14

• reduces genetic diversity population because it can fix alleles or eliminate them

Question 15

When is an allele fixed?

Answer 15

• an allele is fixed when it has a frequency of 1,0 or 100% (and the other allele is now 0=lost)
• the overall effect is to REDUCE GENETIC DIVERSITY, which has conservation implications

Question 16

When does the founder effect occur?

Answer 16

• occurs when a few individuals become isolated from a larger population and start a new small population
• ex. finches blown onto small islands
• allele frequencies in the small founder population can be DIFFERENT (“sampling error” like drift) form those in the larger parent population (reduced number of alleles due to small founder population)
• reduced genetic diversity and new gene pool is the result

Question 17

What is the likely fate of most founder populations?

Answer 17

local EXTINCTION (extirpation)

Question 18

What happens when a large population becomes small very quickly and what is the population called?

Answer 18

allele frequencies may change due to chance events (sampling errors again)

• remember the diagram (rare yellow balls (alleles) are more rare compared to blue, and the whites are more likely to be “missed” by sampling error)

Question 19

What is the bottleneck effect

Answer 19

• a sudden reduction in population size due to a change in the environment (disease, parasites, climate, etc)
• the resulting smaller gene pool may have lost some rare alleles
• if the population remains small, it may be further affected by genetic drift and inbreeding

Question 20

how were cheetahs affected through the bottleneck effect?

Answer 20

• cheetahs went though bottleneck, very low genetic variability, and more prone to extinction, leads to CONSERVATION CONCERNS

Question 21

Explain the bottleneck effect using the exmaple with Northern Elephant Seals at the Pacific Coast

Answer 21

• pop reduced to perhaps 20 individuals in 1890s due to hunting
• current population ranges from 30000 to 100000
• scientists examined 24 genes but found no allelic variation (each gene had only 1 allele)
• this is HIGH HOMOZYGOSITY (fixed and lost alleles) as would be predicted by genetic drift theory and bottlenecking

Question 22

What is mutation

Answer 22

Ultimate source of heritable variations

Question 23

What are the 3 things that mutation can be

Answer 23

1. Deleterious (genetic diseases) 2. Neutral (MN blood alleles and many others) 3. Beneficial (may produce adaptive change)

Question 24

What are the 3 different levels that mutation can act on?

Answer 24

1. point mutations of DNA (change in nucleotides) 2. gene duplication (chromosome pieces copied) 3. genome duplication (polyploidy, multiple copies of whole genomes)

Question 25

What is an important point about mutation?

Answer 25

- only mutations that occur in germ lines (ex. cells that produce gametes and offsprings) are passed onto the next generation

Question 26

What is an error of meiosis?

Answer 26

- if homologous chromosomes fail to separate, the gametes may be diploid (2N) instead of haploid (n) - failure of cell division after chromosome duplication gives rise to tetraploid tissue