Introduction to E.6•Natural selection extended tosocieties•Consider selfish genes as the unitof natural selection•Advanced social structures arebased on kin selection •Consider the game known as the prisoner’s dilemma
The Prisoner’s Dilemma Sells friend out (betrayal) A Keeps quiet (cooperation)Sells friend out A is jailed for life, B (betrayal) Both are jailed for life gets releasedB Both are jailed for a(cooperation) Keeps quiet B is jailed for life, A year and remain gets released friends :-)
Social structure of the eusocial Honeybees • Honeybees organise themselves into the following hierarchy • Queen - Diploid, fertile, lays eggs, female (quite obviously) • Workers - Diploid, female, workers • Drones - Haploid, male, useless except for sex
Social organisation of elephants• The african elephant lives in herds or 10-20 females• The herd is lead by a matriarch female• Any calf may suckle on any nursing cow
Mathematics behind altruism• Hamilton’s Law: rB > C• r = relatedness between the recipient and the altruist • e.g. r = 0.5 between a parent and a child• B = reproductive beneﬁt(s)• C = reproductive costs
TWO EXAMPLES OF ALTRUISTIC BEHAVIOUR IN NONHUMAN ANIMALS
FORAGING BEHAVIOUR• FOOD is essential (well duh)• Advantage of foraging: gaining Calories• Animals tend to optimise foraging • Such that energy gained > energy spent• Consider the cost-beneﬁt analysis
Small-Mouth Bass• The bass has two main food sources. • Minnows - easy to digest, more energy/unit, more difﬁcult to catch • Crayﬁsh - more difﬁcult to digest, less energy/unit, easy to catch
FORAGING BEHAVIOUR of the BLUEGILL FISH daphnia aka water ﬂeas
Male Selection leads to Exaggerated Traits•Consider the peacock•Peacocks long tail = exaggerated so female picks = more offspring but too much isn’t good = extreme = attract predator.
Rhythmical Behaviour Patterns• Animals often show behaviour which appears rhythmic• Daily patterns are regulated by biological clocks or external environmental clues
Rhythmical Behaviour Patterns - Magicicada• Some species emerges every 17 years, Others every 13 years or 7 years• Life is spent underground as a nymph, with a few days after emergence as an adult to breed• Advantageous because of predator’s inability to coordinate their own cyclic behaviour to a prime number
Rhythmical Behaviour Patterns - Fiddler Crab• Their courtship is based on the phases of the moon• The lunar cycle determines the best tidal periods for the release of crab eggs• Advantageous because the crab eggs need the tide to be transferred to the open ocean, where crab larvae thrive
1. Describe a drone.A drone is a haploid male honeybee that does nothing but have sex with the queen bee.
2. Give an example of altruistic behaviour that was not discussed.
3. In high prey density conditions, what size of Daphnias do bluegill ﬁsh prefer?
3. In high prey density conditions, what size of Daphnias do bluegill ﬁsh prefer? Large
4. Identify one problem with altruistic behaviour over evolutionary time.
4. Identify one problem with altruistic behaviour over evolutionary time.The behaviour may linger on while its beneﬁts may no longer be there (e.g. dolphins helping whales, our own tendency to donate to places like Africa)
5. How is it that peacocks are able to survive to lay eggs even with a tail that obviously exposes them to predators?
5. How is it that peacocks are able to surviveand lay eggs even with a tail that may expose them to predators? Lame joke alert... only peahens lay eggs