L12 Altruism in social insects

What is the BIG evolutionary puzzle of eusocial insects?

Why would individuals give up their own reproduction and become sterile workers?

What is the central evolutionary goal according to the lecture?

Passing on genes to future generations (“producing grandchildren”).

What are the 2 reproductive paths mentioned in the recap?

1. Reproduce yourself

Why can helping relatives still be evolutionarily beneficial?

Because relatives share copies of your genes.

What is kin selection?

Natural selection favoring behaviors that help relatives reproduce because relatives share genes.

What is the key intuition behind kin selection?

Genes can spread indirectly through relatives, not only through your own offspring.

Why does the lecture say “production of grandchildren is what counts”?

Because evolution favors long-term transmission of genes, not necessarily direct reproduction.

Why can sterility evolve in eusocial insects?

Helping close relatives can sometimes spread more of your genes than reproducing yourself.

What is altruism?

Behavior that benefits another individual at a cost to the actor.

Difference between cooperation and altruism?

Cooperation = both benefit

What is eusociality?

The highest level of social organization.

What are the 3 defining features of eusociality?

1. Cooperative care of young

2. specialised castes

3. sterile individuals

Why is eusociality considered the most extreme form of kin selection?

Because sterile workers completely give up their own reproduction to help relatives reproduce.

What are castes?

Specialized groups with different tasks (queen, workers, soldiers, foragers).

What is the core intuition behind castes?

Division of labor increases colony efficiency.

Why is communication crucial in eusocial insects?

Colonies require coordination between many individuals.

Examples of eusocial communication?

Pheromones

What does the waggle dance communicate?

Direction of food

What is the intuition behind the waggle dance?

It functions like an insect GPS system.

What is self-organization?

Complex colony structures emerging from simple local rules without a central planner.

Example of self-organization?

Termites building giant nests without an architect.

In which insect groups did eusociality evolve?

Hymenoptera (ants, bees, wasps)

Why is eusociality evolutionarily successful?

Cooperation and specialization make colonies extremely efficient.

What are the 2 key ecological factors favoring eusociality?

1. Life insurance (i can die in peace)

2. Fortress
   defence (together stronger)
   

What is life insurance?

If one important individual dies, helpers can continue raising relatives and maintaining the colony.

What is fortress defence?

Group living helps defend valuable nests/resources.

Why are fortress defence and life insurance especially important in insects?

Many insects depend heavily on protected nests and long-term brood care, making cooperation highly beneficial.

Why are sterile castes rare in vertebrates?

Less fortress-based ecology

Why is monogamy crucial for eusociality?

It keeps siblings highly related, making helping behavior genetically worthwhile.

What is strict lifetime monogamy?

One male and one female mate exclusively for life.

Why does monogamy increase relatedness?

All offspring become full siblings instead of half-siblings.

Why is high relatedness important?

Helping highly related siblings spreads more of your genes.

What is haplodiploidy?

Females develop from fertilized eggs (diploid)

In which group is haplodiploidy found?

Hymenoptera (ants, bees, wasps).

Why does haplodiploidy increase relatedness between sisters?

Haploid males produce identical sperm, making sisters share ~75% of genes.

Why is 75% relatedness evolutionarily important?

Workers may gain more genetic benefit from raising sisters than producing their own offspring.

Do termites have haplodiploidy?

No, termites are normal diploid organisms.

Then why did termites still evolve eusociality?

Strong monogamy

What does the lecture want you to realize about haplodiploidy?

It helps eusociality evolve, but it is NOT the only explanation.

What is the conflict between queen and workers?

Conflict over the sex ratio of offspring.

Why does the queen prefer a 1:1 sex ratio?

She is equally related to sons and daughters.

Why do workers prefer more sisters?

Workers are:

What sex ratio do workers evolutionarily favor?

Female-biased investment (~3 females : 1 male).

What is the intuition behind the sex-ratio conflict?

Queen and workers cooperate overall, but their genetic interests are not identical.

How can workers influence sex ratio?

Feeding female larvae more

What larger lesson does the sex-ratio conflict teach?

Eusocial colonies contain both cooperation AND evolutionary conflict.

What is the core conceptual takeaway of the entire lecture?

Evolution can favor helping relatives reproduce when indirect genetic benefits outweigh direct reproduction