In the "typical" menstrual cycle, day 13 or 14 is when
A) the corpus luteum disintegrates.
B) progesterone levels peak.
C) menstruation begins.
D) ovulation occurs.
E) estrogen levels reach their lowest point.
D
You might also like to view...
Today, the fossil record
A. can be dated only with one layer in relation to older layers below and younger layers above, no actual dates can be estimated. B. can be dated reasonably well only with uranium-238. C. can be dated reasonably well using a variety of radioactive isotopes with known half-lives. D. can be dated precisely, to within a single year, using radioactive isotopes. E. can be dated precisely, to within a single year, using DNA hybridization.
Salamanders are amphibians with very interesting mating rituals. The males perform speciesspecific dances that attract females to mate
Male salamanders deposit spermatophores (mucus packets filled with sperm) on leaves, twigs, or the ground and guide females over them so females can take them up into their cloaca. Mating dances like this result in internal fertilization in many salamander species. Which of the following statements best explains why salamanders are not entirely terrestrial in spite of exhibiting internal fertilization in many species? A. Salamanders require water for gas exchange B. Salamanders simply lay their eggs near the water in which they live. C. Internal fertilization is the first necessary step towards non-dependence of water for reproduction. D. Salamanders do not produce amniotic eggs, therefore they require water for reproduction because eggs need protection from desiccation. E. Internal fertilization only occurs in species where reproduction does not require water. Salamanders simply lay their eggs near the water in which they live.
You are conducting a genetic screen using Caenorhabditis elegans embryos to isolate mutations affecting anaphase (A). Therefore, you need to look for embryos in which
A. the poles do not move apart. B. the spindle apparatus does not disassemble. C. the centromeres do not move toward the poles. D. sister chromatids are mismatched and therefore fail to separate.
A group of ten tomato plants are germinated and maintained in a large tray with no drainage. After several weeks they all begin to wilt and die despite repeated watering and fertilization. The most likely cause of this die-off is _____
A) competition for resources B) a lack of oxygen for the roots C) organic nutrient depletion D) no room left for root growth