An ovum moves from an ovary into the uterine tube where its migration toward
the uterus is aided by the peristaltic
contractions of the smooth tissues of the
uterine tube's walls.
Which statement identifies the body systems that are directly involved in the interaction
described and explains how they accomplish the interaction?
A The nervous system produces hormones that stimulate the ovum, and the circulatory
system moves the ovum into the uterine tube.
B The circulatory system supplies the uterine wall with oxygenated blood, and the
immune system prevents damage to the ovum.
C The reproductive system produces the ovum, and the muscular system causes the
migration of the ovum by peristaltic contractions.
D The excretory system expels the ovum from the ovary, and the nervous system causes
the contractions of the smooth tissues of the uterine wall.

The gene that causes sickle-cell disease is present in a higher percentage of residents of sub-saharan africa than among those of african descent living in the united states. even though this gene causes sickle-cell disease, it also provides some protection from malaria, a serious disease that is widespread in sub-saharan africa but absent in the united states. discuss an evolutionary process that could account for the different percentages of the sickle-cell gene among residents of the two regions.

After getting the slide and microscope ready, stella is eager to see the microscopic pond water specimen! she crouches around her microscope and aligns her eye with the microscope’s eyepiece. but she's only able to see a bright white light. at this point, no specimens or cells are visible on stella's pond water slide. after taking a moment to collect her thoughts, stella realizes she can't see any lifeforms because .

The tasmanian devil, a marsupial carnivore, is facing extinction due to devil facial tumor disease (dftd) which causes bulging cancerous lumps and lesions to erupt around the face and neck — often causing enough deformation to make seeing or eating difficult. dftd has evolved into a contagious cancer, a trait that is unique among cancers. devil mating behavior involves biting around the head and neck, allowing cells from one individual — especially cells from the crumbly dftd tumors — to be transferred to the wounds or face of a new individual. this marsupial was once found across australia, but sea levels rose, isolating the tasmanian population, while the australian population went extinct. what would be an outcome of genetic isolation that is likely to have impacted the spread of dftd? a) reduced territory puts diseased individuals in greater contact with non-diseased ones. b) inbreeding results in less variation in facial features so the cancer is generally fatal. c) genetic isolation has made it difficult for scientists to develop a vaccine against dftd. d) the lack of genetic variation in the immune system of tasmanian devils minimizes resistance to the disease.