Propose an experiment to test the hypothesis that cells from only one region of a frog blastula form the ectoderm. What results from this experiment would support this hypothesis?

How do spermatogenesis and oogenesis in humans differ with respect to numbers of cells produced, gamete size, and timing of the second meiotic division?

Which statement about human reproduction is true?(A)Fertilization occurs in the vagina.(B)Spermatogenesis and oogenesis both require normal body temperature.(C)An oocyte completes meiosis after a sperm penetrates it.(D)The earliest stages of spermatogenesis occur closest to the lumen of the seminiferous tubules.

Which statement about human reproduction is false?a. Fertilization occurs in the oviduct.b. Spermatogenesis and oogenesis require different temperatures.c. An oocyte completes meiosis after a sperm penetrates it.d. The earliest stages of spermatogenesis occur closest to the lumen of the seminiferous tubules.

Give examples of negative and positive feedback in hormonal control of the human menstrual cycle. Why can a high estradiol level be considered a 'readiness' signal from a follicle?

After a sperm penetrates an egg, it is important that the vitelline layer separate from the egg so that it can a. secrete important hormones. b. enable the fertilized egg to implant in the uterus. c. prevent more than one sperm from entering the egg. d. attract additional sperm to the egg.

The BMI z-score is a relative measure of body mass index (BMI) that takes into account age. Higher values represent heavier individuals for a given height. The table here shows the BMI z-score of pre- and post-pubertal girls at three ages. Which of the following conclusions can you draw from the data?a. At a given age, there are more girls with low BMI z-scores than with high BMI z-scores.b. At a given age, girls with high BMI z-scores are more likely to have begun puberty than girls with low BMI z-scores.c. Girls 11, 12, and 13 years of age are equally likely to have begun puberty.d. There is no relationship between BMI z-score and age of beginning puberty.

In the 1960s, the U.S. Food and Drug Administration approved a contraceptive that allowed women to plan desired pregnancies and prevent unwanted pregnancies. Oral hormonal contraception ('the pill') uses synthetic hormones similar in structure to progesterone and/or estradiol. What is the pill's mechanism of action?Which of the following is the most effective form of contraception?a. condomb. diaphragmc. withdrawald. the pill

How does a zygote differ from a mature egg? a. A zygote has more chromosomes. b. A zygote is smaller. c. A zygote consists of more than one cell. d. A zygote divides by meiosis.