Study Guide 3 Flashcards
Anisogamy (also called heterogamy)
refers to a form of sexual reproduction involving the union or fusion of two dissimilar gametes (differing either in size alone or in size and form) —The smaller gamete is considered to be male (sperm cell), whereas the larger gamete is regarded as female (egg cell).
The form of heterogamy that occurs in animals is oogamy. In oogamy, a large, non-motile egg cell (ovum) is fertilized by a small, motile sperm cell (spermatozoon). The large egg cell is optimized for longevity, whereas the small sperm cell is optimized for motility and speed. The size and resources of the egg cell allow for the production of pheromones, which attract the swimming sperm cells.
Isogamy
is a form of sexual reproduction that involves gametes of similar morphology (similar shape and size), differing only in allele expression in one or more mating-type regions. Because both gametes look alike, they cannot be classified as “male” or “female.” Instead, organisms undergoing isogamy are said to have different mating types, most commonly noted as “+” and “-“ strains, although in some species there are more than two mating types (designated by numbers or letters). Fertilization occurs when gametes of two different mating types fuse to form a zygote.
Mutualism
Mutualism is the way two organisms of different species exist in a relationship in which each individual benefits. Similar interactions within a species are known as co-operation. Mutualism can be contrasted with interspecific competition, in which each species experiences reduced fitness, and exploitation, or parasitism, in which one species benefits at the expense of the other. Mutualism is a type of symbiosis. Symbiosis is a broad category, defined to include relationships that are mutualistic, parasitic, or commensal. Mutualism is only one type.
Eusociality
Eusociality the highest level of organization of animal sociality, is defined by the following characteristics: cooperative brood care (including brood care of offspring from other individuals), overlapping generations within a colony of adults, and a division of labor into reproductive and non-reproductive groups. The division of labor creates specialized behavioral groups within an animal society which are sometimes called castes. Eusociality is distinguished from all other social systems because individuals of at least one caste lose the ability to perform at least one behavior characteristic of individuals in another caste. Eusociality is mostly observed and studied in ants, bees, wasps and termites.
For example, a colony has caste differences; a queen and king take the roles as the sole reproducers and the soldiers and workers work together to create a living situation favorable for the brood. In addition There are known eusocial vertebrates like the mole rat. Most of the individuals cooperatively care for the brood of a single reproductive female (the queen) to which they are most likely related to.
Haplodiploidy
Haplodiploidy is a sex-determination system in which males develop from unfertilized eggs and are haploid, and females develop from fertilized eggs and are diploid. Haplodiploidy determines the sex in all members of the insect order Hymenoptera (bees, ants, and wasps).
In this system, sex is determined by the number of sets of chromosomes an individual receives. An offspring formed from the union of a sperm and an egg develops as a female, and an unfertilized egg develops as a male. This means that the males have half the number of chromosomes that a female has, and are haploid.
Lek polygyny
Lek polygyny is a mating system common in polygynous species of insects and birds in which the male provides no parental care to its offspring. The lek mating system is uniquely driven by the females’ pursuit of their mate, rather than the males’. Males of lekking species do not hunt for receptive females. Males form aggregates in neutral locations devoid any resources valuable to females. The group of males performs intricate vocal, visual or chemical displays to lure receptive females to their lekking site. In most lekking species, these group displays typically increase the ratio of visiting females per males. At the lekking site, visiting females are able to compare the males’ physiques and courtship displays, picking the most attractive male as their mate (Alcock, 2001). Thus, the few, most attractive males will do the majority of the mating (about 99%), while the subordinate males do no mating at all (Sherman, 1999).
lek paradox
Persistent female choice for particular male trait values should erode genetic variance in male traits and thereby remove the benefits of choice, yet choice persists. The enigma of how additive genetic variation is maintained in the face of consistent female preference is named the “lek paradox.” This paradox can be somewhat alleviated by the occurrence of mutations introducing potential differences, as well as the possibility that traits of interest have more or less favorable recessive alleles.
The basis of the lek paradox is continuous genetic variation in spite of strong female preference for certain traits. There are two conditions in which the lek paradox arises, the first is that males contribute only genes and the second is that female preference does not affect fecundity. Female selection should lead to directional selection, which would result in a greater prevalence for that trait. Stronger selection should lead to impaired survival because there will be a decrease in genetic variance since more offspring will have similar traits, which is also known as “runaway selection”. Lekking species do not exhibit runaway selection.
Direct fitness benefits
This is also called mutually beneficial cooperation as both actor and recipient depend on direct fitness benefits, which are broken down into two different types: by-product benefit and enforcement.
By-product benefit arises as a consequence of social partners having a shared interest in cooperation. For example, in meerkats, larger group size provides a benefit to all the members of that group by increasing survival rates, foraging success and conflict wins. This is because living in groups is better than living alone, and cooperation arises passively as a result of many animals doing the same thing.
Prisoner’s Delight, another term to describe by-product benefit, is a term coined by Kenneth Binmore in 2007 after he found that benefits can result as an automatic consequence of an otherwise “self-interested” act in cooperative hunting. He illustrated this with a scenario having two hunters, each hunter having the choice of hunting (cooperate) or not hunting (free-riding). Assuming that cooperative hunting results in greater rewards than just a one-player hunt, when hunting is not rare, both hunters and non-hunters benefit because either player is likely to be with other hunters, and thus likely to reap the rewards of a successful hunt. This situation demonstrates “Prisoner’s Delight” because the food of a successful hunt is shared between the two players regardless of whether or not they participated.
It has been shown that free riding, or reaping the benefits without any effort, is often a problem in collective action. Examples of free riding would be if an employee in a labor union pays no dues, but still benefits from union representation. In a study published in 1995, scientists found that female lions showed individual differences in the extent to which they participated in group-territorial conflict. Some lions consistently ‘cooperated’ by approaching intruders, while others ‘lagged’ behind to avoid the risk of fighting. Although the lead female recognized the laggards, she failed to punish them, suggesting that cooperation is not maintained by reciprocity.
Cooperation is maintained in situations where free-riding is a problem through enforcement, which is the mechanism where the actor is rewarded for cooperating or punished for not cooperating. This happens when cooperation is favored in aiding those who have helped the actors in the past. Punishment for noncooperation has been documented in meerkats, where dominant females will attack and evict subordinate females who become pregnant. The pregnancy is seen as a failure to cooperate because only the dominant females are allowed to bear offspring. Dominant females will attack and kill the offspring of subordinate females if they evade eviction and eviction often leads to increased stress and decreased survival.
Enforcement can also be mutually beneficial, and is often called reciprocal cooperation because the act of cooperation is preferentially directed at individuals who have helped the actor in the past (directly), or helped those who have helped the actor in the past (indirectly).
indirect fitness benefits
The second class of explanations for cooperation is indirect fitness benefits, or altruistic cooperation. There are three major mechanisms that generate this type of fitness benefit: limited dispersal, kin discrimination and the green-beard effect. Hamilton originally suggested that high relatedness could arise in two ways: direct kin recognition between individuals or limited dispersal, or population viscosity, which can keep relatives together. The easiest way to generate relatedness between social partners is limited dispersal, a mechanism in which genetic similarity correlates with spatial proximity. If individuals do not move far, then kin usually surrounds them. Hence, any act of altruism would be directed primarily towards kin. This mechanism has been shown in Pseudomonas aeruginosa bacteria, where cooperation is disfavored when populations are well mixed, but favored when there is high local relatedness. Kin discrimination also influences cooperation because the actor can give aid preferentially towards related partners. Since kin usually share common genes, it is thought that this nepotism can lead to genetic relatedness between the actor and the partner’s offspring, which affects the cooperation an actor might give. This mechanism is similar to what happens with the green-beard effect, but with the green-beard effect, the actor has to instead identify which of its social partners share the gene for cooperation. A green-beard system must always co-occur within individuals and alleles to produce a perceptible trait, recognition of this trait in others, and preferential treatment to those recognized. Examples of green-beard behavior have been found in hydrozoans, slime molds, yeast, and ants. An example is in side-blotch lizards, where blue-throated males preferentially establish territories next to each other. Results show that neighboring blue-throats are more successful at mate guarding. However, blue males next to larger, more aggressive orange males suffer a cost.
Nuptial feeding
Nuptial feeding encompasses any form of nutrient transfer from the male to the female during or directly after courtship and/or copulation
Sensory Drive/Sensory Exploitation
Sensory exploitation as an evolutionary origin to nuptial food
Such gifts may arise as a form of sensory trap that exploits the normal gustatory Sensory traps refer to male signals that mimic stimuli
Intrasexual Selection
A form of sexual selection whereby members of one sex compete with each other for access to the other sex.
Intersexual Selection
A form of sexual selection in which individuals of one sex choose which individuals of the other sex to take as mates.
Reciprocal Altruism
The exchange of altruistic acts.
Prisoner’s Dilemma
A game theory payoff matrix that is used to study the evolution of cooperation.
The prisoner’s dilemma (or prisoners’ dilemma) is a canonical example of a game analyzed in game theory that shows why two individuals might not cooperate, even if it appears that it is in their best interests to do so. It was originally framed by Merrill Flood and Melvin Dresher working at RAND in 1950. Albert W. Tucker formalized the game with prison sentence rewards and gave it the name “prisoner’s dilemma” (Poundstone, 1992), presenting it as follows:
Two members of a criminal gang are arrested and imprisoned. Each prisoner is in solitary confinement with no means of speaking to or exchanging messages with the other. The police admit they don’t have enough evidence to convict the pair on the principal charge. They plan to sentence both to a year in prison on a lesser charge. Simultaneously, the police offer each prisoner a Faustian bargain. Each prisoner is given the opportunity either to betray the other, by testifying that the other committed the crime, or to cooperate with the other by remaining silent. Here’s how it goes:
If A and B both betray the other, each of them serves 2 years in prison
If A betrays but B remains silent, A will be set free and B will serve 3 years in prison (and vice versa)
If A and B both remain silent, both of them will only serve 1 year in prison (on the lesser charge)
It’s implied that the prisoners will have no opportunity to reward or punish their partner other than the prison sentences they get, and that their decision won’t affect their reputation in future. Because betraying a partner offers a greater reward than cooperating with them, all purely rational self-interested prisoners would betray the other, and so the only possible outcome for two purely rational prisoners is for them to betray each other. The interesting part of this result is that pursuing individual reward logically leads both of the prisoners to betray, when they would get a better reward if they both cooperated. In reality, humans display a systematic bias towards cooperative behavior in this and similar games, much more so than predicted by simple models of “rational” self-interested action. A model based on a different kind of rationality, where people forecast how the game would be played if they formed coalitions and then they maximize their forecasts, has been shown to make better predictions of the rate of cooperation in this and similar games given only the payoffs of the game.
Facultative altruism
Alturistic behavior that lessens direct fitness but may increase future fitness and reproduction.
Example: helping with nest but having possibility of taking over parental territory in future
MATE COMPETITION
- Members of one sex compete w/each other for access to opposite sex (INTRASEXUAL SELECTION) (usually male)
- males compete for opportunities to mate, or for more mates
Tests of strength – determine dominance and access to mates
Alternative mating strategies
conditional strategies based on male status
Sperm competition
males compete for increased fertilization success
Mate choice
Members of one sex prefer particular individuals of another sex (INTERSEXUAL SELECTION) (usually female)
M. Anderson
Studied female mate choice of long-tailed widowbird
Manipulated tail length.
Shortened tail- reduced mating success
Elongated tails- increased mating success
“Runaway” sexual selection
Genetic linkage disequilibrium of male traits and female preference (female mate choice theory)
“Healthy Mate” hypothesis
“Healthy Mate” hypothesis:
-avoidance of infection
-based on male physiological performance
(Elaborate male traits indicate condition (health))
- Stress from parasites, infections drain color
- Males in better condition survive infection
- Females choose males whose traits indicate health, thereby avoid infection
