What is natural selection? 1. a process that selects variations that help with survival and that spreads the variations to more offspring
2.a process through which nature selects an individual within a population for extinction
3.a process that causes all populations to gradually increase in size
4.a process that causes random variations to appear in the offspring of every generation

Many birth-control pills release a constant amount of synthetic estradiols and progesterone for 21 days, followed by 7 days when no hormones are ingested. which of the following statements most accurately describes the effects of birth-control pills? -birth-control pills maintain constant levels of estrogens and/or progesterone so there is no surge in lh and ovulation does not occur.-birth-control pills inhibit the development of the uterine lining so implantation of a fertilized oocyte cannot occur.-birth-control pills maintain constant levels of estrogens and/or progesterones and mask the release of the oocyte from the follicle.-the 7 days with no hormones does not allow a thick enough uterine lining to form so a fertilized oocyte cannot implant.