Exam 46: Animal Reproduction

Evidence that parthenogenic whiptail lizards are derived from sexually reproducing ancestors includes ________.

Among human males, both semen and urine normally travel along the ________.

Use the following information to answer the question. Estrogens found in the environment have raised concerns about effects on reproductive health of animals. Researchers studied the effects that estrogens in the water have on sexual differentiation in zebrafish. They exposed embryo-larval (0-21 days post-hatching), juvenile (21-42 days post-hatching), and adult (over 200 days post-hatching) fish to three concentrations of 17β-estradiol (5, 25, and 100 nanograms/liter) that are within the range of concentrations found in water leaving sewage treatment plants in different countries. They then examined the proportion of males and females when the fish exposed at embryo-larval and juvenile stages reached adulthood. Embryo-larval stage fish that had been exposed to 100 ng/l 17β-estradiol resulted in adult populations that had substantially more females than males compared to control groups. Embryo-larval fish that had been exposed to 5 and 25 ng/l of 17β-estradiol did not show a statistically significant shift in the proportion of females. (Brion, F., C. R. Tyler, X. Palazzi, B. Laillet, J. M. Porcher, J. Garric, and P. Flammarion. 2004. Impacts of 17β-estradiol, including environmentally relevant concentrations, on reproduction after exposure during embryo-larval-, juvenile-, and adult-life stages in zebrafish (Danio rerio). Aquatic Toxicology 68:193-217.) You are assigned to write the report to the Environmental Protection Agency that needs to decide what level of 17β-estradiol to permit in sewage output. You do not want to make the level any lower than necessary, because it requires substantial additional money for the extra treatment of sewage. Given the data presented, what concentration of 17β-estradiol would you suggest is safe to prevent feminization of fish?

Asexual reproduction results in greater reproductive success than does sexual reproduction when ________.

In correct chronological order, the three phases of the human ovarian cycle that gives rise to a mature oocyte are ________.

You decide to study two species of birds, both of which form monogamous pairs (one male and one female). In species 1, you find that the eggs in a pair's nest are in fact almost always the offspring of that pair. In species 2, you are surprised to find that many of the eggs in a nest were actually fathered by males of neighboring pairs. Apparently, mating outside of monogamous pairings is widespread in species 2. Given this information, what would be the logical prediction to make before comparing testes size of males of the two species?

In excreted urine, a reliable "marker" that a pregnancy has initiated is ________.

Among nonmammalian vertebrates, the cloaca is an anatomical structure that functions as ________.

A primary response by the Leydig cells in the testes to the presence of luteinizing hormone is an increase in the synthesis and secretion of ________.

Refer to the following figure, which diagrams the reproductive anatomy of the human male, to answer the question. In the figure, which letter points to the prostate gland?

Refer to the following figure, which diagrams the reproductive anatomy of the human female, to answer the question. In the figure, which structure is the site of embryo implantation?

Regeneration, the regrowth of lost body parts, normally follows ________.

In correct chronological order, the three phases of the human uterine cycle are ________.

Which hormone is released from the Sertoli cells that inhibits the release of follicle stimulating hormone?

Mature human sperm and ova are similar in that they ________.

Environmental cues that influence the timing of reproduction generally do so by ________.

In close comparisons, external fertilization often yields more offspring than does internal fertilization. However, internal fertilization typically offers the advantage that ________.

A male's "primary" sex characteristics include ________.

At the time of fertilization, the maturation of the human oogonium has resulted in ________.

Sexual reproduction ________.