Oct. 12; Foraging and Sexual Reproduction

In this class we discuss the different aspects of foraging  and sexual reproduction in the animal kingdom.

Foraging Behavior

Aposematism
Aposematism is a coloration of an individual that repels predators. The formation of this color repellent was able to evolve because the individual who was wounded did not die, but was not eaten. This individual was able to pass on its genes. The predator also needs to be able to remember that the color mean toxic.

Optimal Foraging
In optimal foraging you are going to get the most amount of food for the least amount of energy. This also increases the energy available for reproduction. The optimal foraging theory predicts than an animal should behave in a way that maximizes the benefits, minimizes the costs, and in turn will maximize the net energy gain.

We can look at various species to see if they are foraging optimally. The main thing that could determine the ability to forage optimally is the present of a predator. This will push the individual into a sub-optimal environment.

Profitability of Prey
Profitability of prey is the energy gained per unit of handling time. An example of the reduction of optimal foraging is seen in young garden skinks. Their foraging success is lowered in order to reduce the risk of predation. When the number of there are predators sensed there are a smaller number of active lizards, but when you have coverage by a micro-habitat the percentage of lizards that are active increases.

Alternative Foraging Strategies

Frequency-Dependent Selection
Frequency-dependent selection is genetically based strategy. As the percentage of a prey species with a specific trait increases overtime it will be consumed more of the time. The predator will eat the more common morph. So, overtime as the the abundance morph will start to decrease, and the other morph will increase. The genotype with a rare genotype is less likely to be consumed. As oscillation of  morph frequency will become apparent.

Example:
The percent frequency of a blue morph butterfly is larger than an orange morph butterfly. As the more abundance blue morphs are being predated upon, the orange morph will produce more offspring and become more and more frequent. The blue morph becomes more rare because of predation, and the orange morph is more frequent. The predator will then consume the more frequent orange morph. The blue morphs will then be able to reproduce more while the orange morphs are being killed. The occilation of morph frequency starts to appear.

Conditional Strategies
Conditional strategies are an inherited mechanism that give the individual the ability to be flexible. The foraging strategies shift from being a predator, competitor, scavengers or commensals. The behavior depends on the environment, but the mechanism to be flexible is genetically inherited.

Geographical Separation/Divergence

The Evolution of Reproductive Behavior

Sexual Selection
Sexual selection involve traits that lower survival, but enhances the ability to mate. Sexual selective traits are anything that increases the chance of an individuals getting their genes into the next generation based on their ability to mate. The trade off with the increased ability to mate is with its survival ability. The traits can increase their chances of being predated on, decrease foraging ability, ect.

The variation in reproductive success is greater for males than for females. There are a few individuals who get most of the mates, and many individuals who never mate or mate infrequently as a male. The female do not vary as much in how many times they mate, or how many mates they have. The theory of the variation between males and females are the cost of their gametes. The female have fewer and less frequent production of the egg, and at a higher energy cost. The males produce many sperm and will mate with many individuals. Females will be choosy. This produces a conflict between males and females, the operational sex ratio.

Operational Sex Ratio
The actual sex ratio in the field is 50/50 between males and females, but the operational sex ratio tend to be heavily male biased. That means there are a lot more males running around that are sexual active. The females, once their eggs are fertilized, will stop looking to take care of their egg. This male biased ratio is very common.

The operational sex ratio can be reversed where the ratio is heavily female biased. This can occur when males are focused more on other survival behaviors like foraging.

 

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