Lecture 14 Flashcards
What is altruistic behaviour and give an example
- 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
How can you explain the existence of altruistic behaviours in some animals?
- most cases in animal studies determine that altruism usually happens in support of CLOSE GENETIC RELATIVES (also known as “kin”)
What is inclusive fitness?
- direct fitness + infirect fitness
WILLIAM HAMILTON redefined fitness based on both components
What is the concept of “Kin selection”
- selection arising from the indirect benefits of helping relatives raise offspring, rather than reproducing yourself is often the result of altruistic behaviour
What is the Hamilton RUle
- 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
Review the coefficient of relatedness
- 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
Why is the frequency of alarm calling the highest in females of reproductive age?
- 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)
Do black-tailed prairie dogs prefer to help relatives when they give an alarm call? - answer the conclusion of the experiment
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
What does the Hamilton’s rule do and does not do?
- does NOT help animals make decisions consciously
- DOES provide a model for understanding how genes that contribute to altruism can increase through kin selection
Define fitness
- an individual’s contribution of genes to the next generation, relative to other individuals in the population
What are the direct and indirect ways an individual can maximize his or her own fitness?
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
Give an example of inclusive fitness
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
review the florida scrub jays defending their nest (helper research)
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.
What is genetic drift?
- 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
does genetic drift affect small or large populations more
- the effects of genetic drift are strongest in very small populations