Question

Compare the coefficient of relatedness between brothers and sisters in diploid organisms versus those organisms who are haplodiploid. What differences would this lead to in terms of altruistic behaviors?

Answer 1

In diploid organisms both male and female have two sets of chromosomes. The male sperm contains one of its two sets and in the same way female egg contains one of its two sets. So when fertilisation occurs the fertilised egg bears two sets of chromosomes; in which half is from the male and half from the female. So, the average degree of relatedness between brothers and sisters who are diploid is 50%.

In haplodiploid organisms, male contains only one set of chromosomes. This is because the male develops from an unfertilised egg. So, each sperm contains the same set of one type of chromosomes. In other word it passes its 100% genes to the next generation. However, here the females remain diploid. It has two sets of chromosomes. Each egg contains on of the sets. So, in case of haplodiploid organisms we can say that males are 100% related to the female mother while all mothers are only 50% related to their sons. Females are 50% related to their mother and 50% to their father. Also, the fathers are 100% related to their daughters. In case of haplodiploid organisms sisters are 75% related to each other. This is because they receive 50% of their genes from their father and 25% from their mother.

Altruism refers to a behavior possessed by an individual that increases the fitness of one organism and decreases the fitness of another organism.