Trait reproductive

Reproductive Toxicity. No data are available that impHcate either hexavalent or trivalent chromium compounds as reproductive toxins, unless exposure is by way of injection. The observed teratogenic effects of sodium dichromate(VI), chromic acid, and chromium (HI) chloride, adininistered by injection, as measured by dose-response relationships are close to the amount that would be lethal to the embryo, a common trait of many compounds (111). Reported teratogenic studies on hamsters (117,118), the mouse (119—121), and rabbits (122) have shown increased incidence of cleft palate, no effect, and testicular degeneration, respectively. Although the exposures for these experiments were provided by injections, in the final study (122) oral, inhalation, and dermal routes were also tried, and no testicular degeneration was found by these paths. 

A functional explanation for a particular trait does not stipulate by which mechanism within the organism a particular effect is produced. The function can be realized in physically different ways and the only relevant feature is that it must enhance fitness, i.e. serve survival and reproduction (Macdonald, 1992). Various causal factors can then be invoked to explain how the function is performed, although these factors cannot explain why the traits are present unless an appeal is made to selection pressure. 

Robert Richards. So when you have those traits, which do not seem to have any purchase on success and reproduction, then I think you re perfectly right to be very sceptical about that, but take some other kinds of traits, something that is almost as ambiguous as rape. Because rape occurs under a lot of different conditions and in some cases you re not quite sure how to evaluate the behaviour and so on. But, as we were talking at coffee, what about maternal attachment Now that s a fairly vague concept as well. It is the kind of response a mother will have for an infant. That attachment, and again, very often vaguely described, but one can focus on particular aspects of it. Let me just ask you - do you think this is ripe for evolutionary analysis So that s the basic question. 

A parasite must reproduce to complete its life cycle successfully. In this sense, the ability of an H. glycines individual to parasitize a soybean plant is measured by reproduction. In general, resistant hosts do not permit the female nematode to develop to reproductive maturity. Parasitism is a qualitative trait that the individual nematode either does or does not possess. In addition, nematode populations may be described quantitatively by their level of reproduction on a given host plant. Field populations of H. glycines... 

Most social insects are found in the order Hymenoptera. Sociality in insects is defined by the presence of one or more of the following traits (1) individuals of the same species cooperate in caring for the young (2) there is a reproductive division of labor, with usually sterile individuals working on behalf of fecund individuals and (3) there is an overlap of at least two generations in life... 

It is also important to understand the source and significance of genetic variations. The Pima Indians have the highest rates of diabetes in the world Tay-Sachs disease is primarily found in Ashkenazi Jews. Contemporary literature indicates that these differences stem from reproductive isolation, not race. Genetic traits common to persons with sickle-cell disease are related to malaria frequency and not our social view of race. This is why the disease can be found in high frequency in Yemen, West Africa, Greece, and Saudi Arabia. 

A polymorphism can be a risk factor for an individual s health or life expectancy without impairing its reproduction. This appears to be the case for many common human diseases, which manifest themselves only after the generative period, so that evolutionary selection against such a trait cannot be operative. 

Positive social behaviors, including gregariousness and the formation of social bonds, are less frequently studied than reproductive and agonistic behaviors, but are critical for primate reproduction. Agonistic behavioral traits associated with androgen exposure may be in conflict with social behaviors needed for courtship, the formation of social bonds and subsequent parental behavior. Higher levels of male sociality are probably nec-... 

Of 50 adult rats used in a reproductive/developmental study, 22% of those that received 6 mg/kg/day heptachlor in the diet developed lens cataracts 4.5-9.5 months following exposure. In addition, 6-8% of the pi offspring and 6% of the p2 offspring of these rats also developed cataracts 19-21 days after birth (Mestitzova 1967). The author of this study eliminated the possibility of a vitamin B deficiency or a recessive genetic trait as the cause of the cataracts. She could not rule out the possibility of altered vitamin B metabolism caused by heptachlor. 

Depending upon the circumstance and desired effects, endocrine-disrupting chemicals can be either good or bad. The endocrine system is a finely balanced system responsible for fertility and many of the feminine and masculine traits we are all familiar with. Endocrine disruptors are used by millions of women in the form of the pill to control fertility. Chemicals in birth control pills subtly manipulate the endocrine system to reduce fertility. Unfortunately, we now know that many chemicals are capable of influencing the endocrine systems. When these chemicals, such as DDT and TCDD, are released into the environment, they reduce the fertility of wildlife. Exposure to endocrine disruptors is linked to decreased fertility in shellfish, fish, birds, and mammals. Endocrine disruptors such as nonylphenol have been shown to feminize male fish, interfering with reproduction. Some studies have also linked exposure to endocrine disruptors to decreases in human male sperm count. Ironically, urinary metabolites of the birth control pill as well as the female hormone estrogen pass through waste treatment plants and are released into the aquatic environment, where even small concentrations cause feminization of male fish. 

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