Kashmeera N.A.Kashmeera N.A.II Sem MSc.ZoologyII Sem MSc.ZoologyRoll no:37Roll no:37Christ collegeChrist college
Natural selection has shaped the behaviour ofdifferent animal species in accordance with thedemands of their different life styles; as the way oflife of a species and its form change overevolutionary time,so does its behaviour.
Under natural conditions,some of the variability between individualswould affect their ability to survive and reproduce successfully.Those variants that were more successful would leave more survivingoffspring and hence their frequency would increase in the population oversuccessive generationsThis is the main reason that behaviour evolves and that differentspecies have come to behave differently,because animals only breedwith their own species & they can evolve characters independently inaccordance with the demands of their surroundings
This type of adaptive evolution is well illustrated by the Kittiwakes
One of the most spectacular displays is the courtship of malepeacock.Comparing the displays of related species can give usa clue about their evolutionary origins.
During evolution new species form by splitting of old ones.The isolated populations then evolve independently in their differentenvironments and their characteristics often diverge.Mating between such distinct populations may result in sterile hybrids andresult in few surviving young ones.In such circumstances natural selection favours distinct colouration anddisplays in the 2 groups so that they can readily recognize and mate withmembers of only their own population.Once this has happened speciation occurs.
Sceloporus lizards-Males defend their territory and try to attract females withhead-bobbing which is different in different species.
Sometimes recognition of the members of the same species is based onlearning by the young of the appearance of their parents
In early 1960s W.D.Hamilton developed genetical theory forevolution of behaviour.This theory revolutionized study of animal social behaviour.Thisapproach is referred to as sociobilogySociobiology is a field of scientific study which is based on theassumption that social behavior has resulted from evolution andattempts to explain and examine social behavior within that context..
E. O. Wilson, a central figure in the history ofsociobiology.While the term "sociobiology" can be traced to the 1940s,the concept didnt gain major recognition until 1975 with thepublication of Edward O. Wilsons book,Sociobiology: The New Synthesis.
““Every man must decide whether he will walk in theEvery man must decide whether he will walk in thelight of creative altruism or in the darkness oflight of creative altruism or in the darkness ofdestructive selfishness”destructive selfishness”–– Martin Luther King JrMartin Luther King Jr
•On occasion, some animals behave in ways that reduce theirindividual fitness but increase the fitness of othersThis kind of behavior is called altruismFor exampleAn adult Ringed Plover willpretend to have a broken wing.to draw the enemy away from itsnest or young.Such altruistic act serves toincrease the chances of survival ofthe offspring but often at some risk tothe parent.
In naked mole rat populations,nonreproductive individuals may sacrificetheir lives protecting their reproductivequeen and kings from predators
Vampire bats will regurgitate and feed blood thatthey have collected from their prey to a hungryconspecific
““You scratch my back & I will scratch yours”You scratch my back & I will scratch yours”
Altruistic behavior toward unrelated individuals can be adaptive if theaided individual returns the favor in the future.This type of altruism is called reciprocal altruism.Eg-Olive baboonIn them male will always help an unrelatedmale in troop to distract the attention of a thirdmale that is guarding a receptive femaleThe soliciting male will take over female whilethe other two are engaged in dispute.In future the favour is returned.
Kin selection is the natural selection that favor thereproductive success of an organisms relatives, even at a cost tothe organisms own survival and reproduction.Charles Darwin was the first to discuss the concept of group/kinselection.In the "The Origin of Species", he wrote clearly about altruisticsterile social insects
Altruistic suicide?Altruistic suicide?•In many social insects, workers notonly forego reproduction, but also theirown life, “for the good of the colony”
Florida scrub jay is a communally breeding bird in which the offsprings assistthe parents in rearing subsequent broods.These are their own siblings and by helping to rear them they are in effectspreading copies of their own genes to the future.
In the 1930s J.B.S. Haldane had full grasp of the basic quantities andconsiderations that play a role in kin selection.He famously said that, "I would lay down my life for two brothers or eightcousins".
Haldane’s father father’s brotherGeneticrelatedness50%(1/2)Geneticrelatedness50%(1/2)HaldaneBrother’s son(Haldane’s cousin)Geneticrelatedness 50%(1/2)Geneticrelatedness1/2x1/2=1/4Geneticrelatedness½ x ½ x ½ = 1/8
Hamilton’s Rule and Kin SelectionHamilton’s Rule and Kin SelectionHamilton proposed a quantitative measure forpredicting when natural selection would favor altruisticacts among related individuals.The three key variables in an altruistic act are:The benefit to the recipient.The cost to the altruist.The coefficient of relatedness.[The coefficient ofrelatedness is the probability that two relatives mayshare the same genes.]
Natural selection favors altruism whenthe benefit (B) to the recipient multipliedby the coefficient of relatedness (r)exceeds the cost (C) to the altruist.rB > CThis inequality is called Hamilton’s rule.Hamilton’s ruleHamilton’s rule
Belding’s Ground squirrelswill warn others of thepresence of a predator, eventhough making such a callmay draw the attention ofthe predator to itself.
The inclusive fitness of an organism is the sum of its classical fitnessand the number of equivalents of its own offspring it can add to thepopulation by supporting others .more generalized than strict kin selection, which requires that the sharedgenes are identical by descent.Inclusive fitness is not limited to cases where kin are involved.inclusive fitness offers a mechanism for the evolution of altruism.this leads natural selection to favor organisms that would behave in waysthat maximize their inclusive fitness.
The most important text on the subject of biologicalaltruism is "The Selfish Gene" by Prof. Richard Dawkins(1976), which explains in great depth and accuracy thebiological nature of selfishness, and argues strongly thatbiological nature is entirely concentrated on theprotection of ones own genes
. It follows that it is possible for an individual to preserve its genesthrough its own self-sacrifice; if a mother dies in the course ofsaving her three offspring from a predator, she will have saved 1½times her own genes (since each offspring inherits one half of itsmothers genes).
“Let us try to teach generosity andaltruism because we are bornselfish” Richard Dawkins (1976).“Scratch an altruist and watch ahypocrite bleed”. Ghiselin