How Is Animal Behavior Passed To Offspring In Dna

Evolution OF BEHAVIOR

1 general view in the written report of the evolution of behavior is that behaviors can have a genetic basis. This is non to say that all behaviors are genetically based; indeed many behaviors are entirely culturally transmitted or learned and may have little to do with genetics (why are you sitting in the same seat?). For genetically influenced behaviors nosotros can treat them as we would care for any other genetically controlled trait of an organism: 1) if there are genetically based differences in a behavior, and ii) these differences impact fitness then, three) behaviors can evolve past natural option.

Two examples of genetically based behaviors: cricket vocal. Different species of crickets have different calling songs with unlike characteristics, due east.grand., inter chirp interval, pulse repetition charge per unit, etc. Hybrids betwixt closely related species oft showroom songs with intermediate characteristics (pulse repetition will exist intermediate, inter pulse interval will be intermediate, etc.) a hypothetical example with time on horizontal axis and each chirp = a group of vertical lines:

Some other example (on a larger phylogenetic scale) is head scratching with the hind leg in amniotes (reptiles, birds, mammals; those with an amniotic sac). Most reach the hind leg over the fore limb to scratch the head; that birds and mammals practice it suggests that this beliefs has a genetically programmed basis and has been inherited through much of higher vertebrate evolution.

Behavior is commonly dissected into 2 components for assay: Proximate causes/questions in which one asks how the beliefs is performed and ultimate causes/questions in which one asks why the behavior is performed. Tinbergen has identified four questions to pose when analyzing a behavior i) what is the cause, 2) what is the evolution (ontogeny), 3) what is the current function 4) what is the phylogenetic history. A strict form on evolution focuses more on the latter ii questions (recall adaptation/preadaptation/exaptation discussion and the identification of current utility vs. historical origin).

Herring gulls brood is large colonies on the basis and defend territories. Two separate calls used for 1) advert nest site ("choking" call) and 2) equally a territorial claim (the "oblique pose" and "long call"). The Kittiwake as well breeds in colonies but nests on vertical cliffs and its nest pad is its territory and breeding site. In this species only i behavior serves both functions: "choking" behavior is both defensive and part of mate recognition/pair formation. This is seen equally an adaptive behavioral shift wit respect to the nest location (steep cliff).

There are many behaviors that at starting time appearance exercise not seem "adaptive". Infanticide in lions was commencement viewed as "aberrant" behavior by abnormal individuals because it was non "good for the species" (male lions displace other males from groups of females and their offspring, and frequently kill the cubs). Information technology is true that killing infants is not, in the short term, an effective means of increasing population numbers of a species. BUT, we now know (mail service West.D. Hamilton'due south 1963, 1964 papers on inclusive fitness and kin selection and G. C. Williams book on Adaptation and Natural Selection) that the more appropriate way to address such bug is to think nearly them in the context of whether the behavior is adept for the individual.

In analyzing infanticide from the perspective of gene thinking it is 1) not adaptive for a male king of beasts to invest reproductive effort in an private with whom he shares no genes and two) once the infant is killed it is advantageous for the female to come into estrous and accept more offspring with the new male (this will increase her reproductive output over leaving with the displaced male, and not benefiting from other advantages of grouping living: foraging, avoiding predation on young). Given the situation for both male person and female person, the observed behaviors brand sense in terms of propagating ones genes.

The role of the factor (or gene due south !) as the unit that is relevant in the evolution play an important office in two influential books in the mid 1970s Sociobiology by E. O. Wilson, and The Selfish Gene past Richard Dawkins. To grossly oversimplify 1 of their chief letters: "an organism is just DNAs way of making more Dna"

If nosotros accept the case of bird migration we want to know how the bird navigates to the convenance location (solar and magnetic cues during flight), how the bird knows when to begin migration (internal clocks and changes in day length [physiological changes]). At that place is normally a loftier cost associated with migration then we also want to know why birds do information technology since many die in the process (more than time for feeding, more available food). Individuals that do drift must leave more offspring than those that do not - once again factor thinking helps account for why the beliefs exists

Population genetic approaches to the development of traits rarely tell u.s. why a phenotype affects fitness in a detail manner; the models usually look at whether fitness increases or not. The optimality approach to the analysis of behavior attempts to builds models where dissimilar behaviors are treated as the traits and asks which one of these behaviors might evolve. The approach generally ignores the mechanics of underlying genetic basis of the beliefs (i.eastward., its mendelian and transmission genetics). Optimal models assume at that place is a genetic basis and treat each behavior as a haploid (asexual) trait that is inherited intact.

While Gould and Lewontin (and many others) have criticized optimal models, the builders of optimal model (e.grand., John Maynard-Smith, Univ. Sussex) argue that the models do not assume that the organisms are optimal (because there are constraints on evolution of traits), just by treating the trouble as an optimality issue, it can tell you what kinds of behaviors might evolve.

Two full general type of optimal models: frequency independent models are designed independent of what other strategies are doing, and seek to define the conditions which might influence beliefs (recall the "optimal foraging" model nosotros described in the accommodation lecture where a bird assess, quality, availability, distance to food items, etc.).

Frequency dependent models are ones where the strategy of one type depends on the strategies and frequencies of other types in the population. The general approach is to look for Evolutionary Stable Strategies (ESS) = a strategy that, if adopted by all, cannot exist "invaded" past a mutant strategy. Here a strategy = the behavior of an individual in a sure state of affairs. These types of model apply nicely to ritualized behaviors, distinct display behaviors which take the place of aggressive interactions. Maynard-Smith's approach involves:

H = hawk who fights until the opponent retreats or will continue fighting injured with cost C

D = dove who displays but volition retreat if the opponent escalates

V = payoff of winning an encounter

C = price of losing an encounter

These values tin be put into a payoff matrix:

		In encounter with:
		H	D
Payoff to:	H	one/2 (5-C)	V
	D	0	V/2

H:H interaction = 1/ii(5-C) because each individual hawk will win half of the fourth dimension and lose half of the time. In the D:D interaction each will win one-half of the time and retreat half of the time (retreat with no toll). Which strategy is an ESS? Reply past asking if a strategy can invade. Can H invade a population of D's?: Is payoff (D against D) > payoff (H against D)? i.east., is V/ii > V? Reply = NO, and then H can invade a population of D'due south.

Is H an ESS? Is payoff (H against H) > payoff (D against H)? i.e., is ane/2(V-C) > 0? Answer: it depends on the values of 5 and C: if V > C then payoff to H will be positive and H is an ESS; if V < C then payoff to H will exist negative and neither D nor H will exist favored (H will always invade a population of D's until H's go and then frequent that they come across each other oftentimes. D tin can invade a population of H'southward because H's tend to damage each other likewise much. In fact a population of all H'south with V<C would go extinct. Thus which behavior evolves depends on the nature of the interactions.

Ane can imagine many other games and payoff matrices that could be built to model other behaviors. The indicate of all this is to imagine the following: some species have ritualized displays that appear "civil" in an anthropomorphic sense. Have these behaviors evolved through a phase where hawks killed each other (C was loftier) to their current land where the cost C to engaging in a behavior is considerably less? This question could be addressed by comparing the behaviors of related species and applying the game theory approach.

Source: https://biomed.brown.edu/Courses/BIO48/16.Evol.Behavior.HTML

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