Kit Library / Science / Evolutionary Biology
⚡ Topic Learning KitShared by a Veda learner · Generated with Veda AI
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💡 Key Idea
Sisters: more than family, an evolutionary edge.
Sisterhood in biology refers to the cooperative bonds between female kin, especially sisters. These bonds are not just social—they are evolutionary adaptations that increase survival and reproductive success. By helping relatives, females can pass on shared genes indirectly, a concept called kin selection.
↳ Sisterhood is nature's way of ensuring shared genes survive.
📖 Definition
Why help family? It's in the genes.
Kin selection is an evolutionary strategy where individuals help relatives survive and reproduce, indirectly passing on their own genes. This explains altruism among sisters: by helping a sister raise offspring, a female ensures shared genetic material continues.
↳ Hamilton's rule: help when the genetic payoff outweighs the cost.
⭐ Important Fact
Half your genes, all your loyalty.
Full sisters share about 50% of their genes, the same as parents and offspring. This high relatedness makes cooperation evolutionarily advantageous. In many species, sisters form coalitions to defend resources, raise young, or compete for dominance.
↳ Genetic overlap fuels sisterly solidarity.
✏️ Example
Lion prides run on sister power.
In African lions, females are the core of the pride. Sisters often hunt together, defend territories, and synchronize reproduction. They even nurse each other's cubs. This cooperative breeding increases cub survival and strengthens the pride's competitive edge.
↳ Lionesses show how sisterhood builds a stronger pride.
✏️ Example
Grandmothers, mothers, daughters: a united front.
Elephant herds are led by the oldest female, often a matriarch. Related females—sisters, aunts, daughters—stay together for life. They share knowledge of water sources, help raise calves, and protect each other from predators. This matrilineal society is a prime example of sisterhood in action.
↳ Elephant sisterhood preserves wisdom across generations.
⚖️ Comparison
Together or alone? The trade-offs.
↳ Sisterhood trades individual competition for collective security.
⚙️ Process
How do animals know who's family?
↳ Kin recognition prevents helping strangers and reinforces sisterly bonds.
🛠️ Application
Grandmothers and the rise of cooperation.
In humans, cooperative breeding and matrilocal societies may have shaped our species. The grandmother hypothesis suggests that post-reproductive women helped daughters raise children, boosting survival. Sisterly bonds also provided childcare, food sharing, and social support.
↳ Human sisterhood may have been key to our evolutionary success.
⚠️ Common Mistake
Even sisters compete.
A common misconception is that sisterhood means zero conflict. In reality, competition for resources, mates, or status can occur even among close kin. However, the benefits of cooperation often outweigh the costs, so sisterly bonds persist despite occasional squabbles.
↳ Sisterhood balances cooperation with competition.
🎯 Exam Tip
Connect genes to behavior.
When asked about sisterhood, always link it to kin selection and Hamilton's rule. Explain how shared genes make altruism adaptive. Use examples like lionesses or elephants to show real-world evidence.
↳ Always tie sisterhood back to genetic benefits.
🧠 Memory Trick
A rhyme to recall kin selection.
Use the phrase 'Sisters Share, So They Care' to remember that genetic sharing (50%) drives caring behaviors. This helps recall why cooperation evolves among female kin.
↳ Shared genes → shared care.
❓ Did You Know
Female bonds keep the peace.
In bonobos, female coalitions—often between sisters and mothers—prevent male aggression and maintain social harmony. Unlike chimpanzees, bonobo females dominate, and sisterhood is central to their peaceful society.
↳ Bonobo sisterhood shows how female bonds can shape entire societies.
The biology of sisterhood explores how cooperative bonds between female kin, especially sisters, are evolutionary adaptations driven by kin selection. Shared genes make helping relatives a way to pass on genetic material…
Full explanation, worked examples & memory tricks in the app
All 17 questions, laddered from warm-up to topper-level, each with its answer and the reasoning behind it.
Q1. Which of the following best defines **kinship** in the context of female bonds?
BeginnerB · Shared genetic relatedness or social ties through descent or marriage
Kinship refers to genetic relatedness or social ties that form the basis for cooperation and altruism among females.
Q2. Which of the following is an example of **female bonding** in primates?
BeginnerD · Female baboons forming grooming alliances
Female baboons often form strong social bonds through grooming, which provides support and reduces stress.
Q3. In the context of **sisterhood**, what is meant by 'female bonds'?
BeginnerB · Social and cooperative relationships among females
Female bonds encompass both kin and non-kin social relationships that involve cooperation and support.
Q4. What is a **matriline**?
BeginnerC · A line of descent traced through females
A matriline is a lineage based on female ancestry, often central to social structure in many species.
Q5. Kin selection can explain altruistic behavior toward nieces and nephews.
BeginnerA · True
Helping relatives like nieces and nephews can increase indirect fitness, as they share genes.
Q6. Female cooperation is always altruistic and never selfish.
BeginnerB · False
Cooperation can be mutualistic or selfish; individuals may cooperate to gain personal benefits.
Q7. In many social mammals, **female philopatry** leads to:
IntermediateD · Females remaining in their natal group, forming close kin networks
Female philopatry means females stay in their birth group, which fosters strong kinship bonds and cooperation.
Q8. Which concept explains why a female might help her sister raise offspring instead of having her own?
IntermediateB · Kin selection
Kin selection favors behaviors that increase the survival of relatives, thereby passing on shared genes.
Q9. **Cooperation** among unrelated females is most likely to evolve when:
IntermediateC · Benefits outweigh costs and reciprocity is possible
Reciprocal altruism can evolve when individuals exchange favors over time, benefiting both.
Q10. Which of the following best describes **reciprocal altruism**?
IntermediateC · Helping others with the expectation of future return
Reciprocal altruism involves exchanging acts of help, with the expectation that the favor will be returned.
Q11. In many cooperatively breeding birds, female helpers are often:
IntermediateD · Offspring from previous broods
Helpers are typically older offspring that delay dispersal and help raise siblings, gaining indirect fitness benefits.
Q12. Which hormone is often associated with **social bonding** and **cooperation** in females?
IntermediateB · Oxytocin
Oxytocin is known to promote trust, bonding, and cooperative behaviors.
Q13. Which of the following is a potential cost of female cooperation?
IntermediateA · Increased risk of exploitation by cheaters
Cooperation can be exploited by individuals who take benefits without reciprocating, posing a cost.
Q14. **Female bonds** in elephants are primarily maintained through:
IntermediateC · Long-term matriarchal leadership and communal care of young
Elephant herds are led by older females and involve cooperative care of calves, strengthening bonds.
Q15. Which of the following is NOT typically a benefit of female social bonds?
IntermediateC · Guaranteed mating opportunities
While bonds offer many benefits, they do not guarantee mating opportunities; mating success depends on multiple factors.
Q16. In spotted hyenas, female dominance is supported by:
AdvancedB · Maternal inheritance of rank and female coalitions
Female spotted hyenas inherit social rank from their mothers and form coalitions to maintain dominance.
Q17. The **grandmother hypothesis** explains:
AdvancedC · Why females live long after menopause
The grandmother hypothesis suggests that post-reproductive females help care for grandchildren, increasing their fitness.
25 flashcards in this kit — the app reviews them with spaced repetition so the right card returns on the right day.
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True False
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Memory Match
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Flashcard Battle
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Sequence Builder
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Revision Battle
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