A Bit of Background Information What is pre- and post-copulatory sexual selection? From the word copulatory, meaning to engage in sexual intercourse, pre-copulatory sexual selection refers to the female's choice in selecting a mate before sexual intercourse takes place. Post-copulatory sexual selection occurs within the female's reproductive track, and it describes the biological selection (whether due to sperm or the female's biology) that results in the fertilization her eggs. Why are guppies good subjects for research in this topic? The most significant reason for using guppies in sexual selection research is because they casually participate in polyandry. This means that in nature a female guppy will mate (willingly or unwillingly) with numerous males at a time, allowing for experiments to be conducted to see which male's sperm fertilizes the most eggs. Why use artificial insemination? Before the use of artificial insemination, the results of such experiments were obscure and varied greatly. There was no way of controlling the males' ejaculate sizes or thier specific sexual contact with the female guppies. By using artificial insemination techniques, these two variables can be controlled: equal quantities of sperm from each male guppy can be isolated, and no sexual contact need ever take place. The increased control over these variables makes it possible to attain reliable results that are directly related to postcopulatory processes. Introduction Sexual selection is a common facet of evolutionary biology that plays a key role in the mating choices of a variety of different species. Competition between the male’s sperm as well as the choice of mate by the female factor into a successful copulation.This experiment examines the precopulatory and postcopulatory behavior of Poecilia reticulata , the guppy. Artificial insemination was used to separate the factors of sexual selection before and after sexual intercourse. “Attractive” males in the guppy population—deemed attractive based on the female guppy’s affinity for them—were those with high levels of carotenoid coloration (orange, yellow, and red). Relative statures were also compared. The purpose of this experiment is to demonstrate, through artificial insemination, the role of postcopulatory sexual selection in a population of guppies. If guppy females are partial to specific traits, the propagation of those traits will be evident. The Methods That Were Used Prior to insemination, the behavior of the guppies involved was analyzed and one adult, non-virgin female and two sexually immature fish were put in observation tanks.
... reproduction for understanding human reproduction, using computer programs and 3-D model. There has been a lot of research on how the egg binds with the sperm. The main evidence uncovered to support the main body of the article was observing the chicken reproduction to show how the egg was fertilized.
The female reproductive system in birds is reduced in most species to a left ovary and oviduct. This unilateral reduction of the female reproductive system is thought to bear two benefits: it reduces the female’s body and it prevent the potential problem of simultaneously carrying two large fragile eggs within the abdominal cavity. It also balances the body with the liver on the right side adjacent to the left ovary.
...to 300 individuals, the newborn seahorses are independent of parental care and the male is free to fertilize and accept more eggs(Lourie 11). The offspring bearing roles displayed by Hippocampus spp. is an extreme shift in relation to many other species of kingdom Animalia, of which the bearing of young is predominantly carried out by females. According to Foster, growth rates throughout the life cycle and the duration of the life cycle of seahorses in the wild varies between species and cannot be determined due to insufficient research data(foster 22). Once sexual maturity is reached, often determined by the presence of a brood pouch in males, adults are able to reproduce. During reproduction, the overwhelming majority of Hippocampus species display monogamous behaviors, usually mating with the same partner for the duration of the mating cycle(lourie 10-11).
This report is on a virtual experiment based on the real-life experiment accomplished by John Endler and David Reznick of the University of California. The goal is attempting to determine whether or not the level of predation effect’s the color patterns of guppies.
Wofford, Sarah Jane. "Sex and Fighting: Male and Female Crayfish Utilize Different Assessment Strategies During Agonistic Behavior." MS thesis Graduate College of Bowling Green, 2013. Web.
The word “monotreme” is Greek for “one-hole,” referring to the cloaca that is the exit for the urinary, reproductive, and excretory systems (Dawson, 1983). The creatures are oviparous--the females lay eggs that develop outside of her body. This paper will explain the background of the animals, the anatomy of the tract and egg, breeding behavior, and genetics behind this unique reproductive system. It will pay special attention to the similarities of the monotreme reproductive system to those of animals we are more familiar with.
... effort is also considered because there is still evidence that in certain species the parental investment theory is not fulfilled. Therefore, males that invest more in mating effort develop increased male mate preference. Finally the last key factor is the difference in adaptive problems that each sex has had to overcome. For males, they evolved strategies to ensure their genes effectively get passed on to the next generation as well as behaviours to enhance paternal certainty while females had to develop strategies that select for the males with the most resources. This is evident today through what males and females find attractive in potential mates. While males look for youthfulness and ability to reproduce females look for wealth and strength. However, both sexes also show similarities and find partners that are symmetrical more attractive. It is important to
The two books examined in this paper, Martin Daly and Margo Wilson's Homicide and David M. Buss's The Evolution of Desire, suggest that human mating strategies have an evolutionary basis. The book written by Martin Daly and Margo Wilson supplies the theoretical groundwork and the book written by David M. Buss gives validity and empirical support for the theory. The two books make a strong scientific argument for evolutionary adaptations as the most crucial element to understanding human sexuality and desire. According to this argument, the key to understanding human sexuality lies in the evolutionary origin of our species.
Sexual selection comes in two forms. One, is direct competition between males for access to females. The other is through the females’ choice among possible mates. (pg. 148) In both types of sexual selection, the males compete for the females. The classic sexual selection arguments that Darwin first presented, were improved when genetics discovered how significant sexual recombination was to genetic variability and speciation. In our class discussion we were asked if animals and humans selected their partners in different ways. I agreed as well as disagreed that we are different in our selection. Humans and animals essentially need the same things, and when looking for a partner there isn’t much of a difference. We all look for the partner with the physical aspects that appeal to another, and for protection, the strongest is typically the best mate in both animal and human worlds. But for humans, emotions come into play, and we also chose on personality. One can have all of the qualifications that are “necessary” in the choosing of a mate, but if their personality does not cohabitate with the other party member, they will not be chosen for a lifelong relationship. Nonetheless, emotional choses may be the only true difference we have to that of
Sex reversal has been observed in reptile species that rely on temperature-dependent sex determination when exposed to high levels of BPA. An example of this can be seen in a study done by Stoker et al. (2003). Researchers found that eggs treated with 90ugBPA/egg produced females when incubated at the male-specific temperature (reviewed by Flint et al., 2012).
1996). A study was done to examine the different parent-juvenile interactions of two different species of poeciliids: P. Monacha and P. Lucida. Individual females of the two species were place into chambers that had a mesh net to segregate it and allow juveniles to swim through and escape attack from the parent. The females were kept in these chambers as they birthed offspring and were recorded. It was found that the p. monacha females cannibalised their offspring immediately while the p. lucida females did not (Thibault 1974). The p. monacha juveniles that did escape the initial attack, swum to the bottom and through the mesh net. However, the juvenile p. lucida remained in the same section of the chamber with the female near the water
It may seem obvious to some why people mate, however there are many facets to human mating. Psychology has shown that reasons for mating have gone beyond the scope of love and physical attractiveness. People may search for mates who resemble archetypical images of the opposite-sex parent, mates with characteristics that are either complementary or similar to one's own qualities, or mates with whom to make an exchange of valuable resources (Buss 238). Although these theories play a key role in understanding patterns in human mating preferences, evolutionary psychology and sexual selection theory provide more concrete frameworks for explaining human mating.
On top of natural selection, Charles Darwin also brought to light the idea of sexual selection. Under sexual selection, sex is more important than life itself. There is a powerful urge to pass our genes on to the next generation in many mammals, even humans (1) Many times sexual selection trumps natural selection, where animals possess traits (such as exaggerated plumage or ornaments) that hinder survival but help them win mates against other males. Darwin figured this out and said “perseverance, strength and size of body, weapons of all kinds, musical organs, both vocal and instrumental, bright colors and ornamental appendages, have all been indirectly gained by the one sex or the other, through the exertion of choice, the influence of love
When a gull has captured a plentiful supply of fish in its neck, the baby will peck at its mother so the fish will be released for them to feed on. The baby gulls will respond to the back and forth swinging and the red dot on the mother’s beak.