Answer to Question 1
Answer: Conception requires: (1) a viable egg; (2) a viable sperm; and (3) access to the egg by the sperm. Examples of methods of contraception and the necessary condition they disrupt would include:
Hormonal birth control methods that suppress ovulation are effective in altering condition (1), the viable egg. Moreover, fertility awareness methods attempt to ensure that a viable egg is not present in the woman's reproductive tract at the same time as viable sperm.
Although many conditionssuch as exposure to heat or certain medicationscan alter the health, number, and motility of sperm, no reliable method of contraception currently exists to safely and effectively oppose condition (2), the viable sperm.
Male sterilization prevents sperm from entering the ejaculatory duct. Female sterilization, withdrawal, and barrier methods such as male and female condoms and spermicide all prevent an encounter between viable sperm and viable egg. These methods alter condition (3), access. In addition, IUDs are thought to block fertilization by affecting the movement of egg and sperm.
Answer to Question 2
Answer: Abstinence means to deliberately avoid intercourse, but can include engaging in kissing, massage, and solitary masturbation. Abstinence is 100 percent effective as birth control and in preventing STIs. Outercourse means engaging in activities such as oral-genital sex and mutual masturbation. Outercourse can be 100 percent effective for birth control but is not 100 percent effective against STIs.
Cross-Sectional and Longitudinal Methods
An example of a selection list used to identify symptoms.
Severe hash is almost always caused by cylinder misfire conditions.
IPM combines biocontrol and chemical methods
Identify the junction nodes in the circuit shown in Figure 21-1.
Transcription Conditions for the lac Operon