In the avian and mammalian eye, the lens remains stationary but changes shape in order to focus on objects at various distances. This is called "accommodation" and is accomplished through adjusting muscle control of the lens in order to
A. control the amount of light admitted to the eye through the pupil.
B. alter the sensitivity of the eye to varying light levels.
C. convert light energy into electrical signals by the retina.
D. bend light rays to varying degrees according to the angle at which light enters the eye.
E. regulate the vitreous humor volume.
Answer: D
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You are a genetic counselor, and a couple comes to you with concerns that if they have a child
together it could have hemophilia. The man has an X-linked recessive form of hemophilia, but the woman does not. Genetic tests reveal the woman is not a carrier for hemophilia. Which of the following would be a correct thing to tell them?
a. Any child that they produce will have a 50% chance of having hemophilia. b. All of their male offspring will have hemophilia, and each of their female offspring will have a 50% chance of having hemophilia. c. None of their offspring should have hemophilia, but all of their female offspring will be carriers for hemophilia. d. Each of their male offspring will have a 50% chance of having hemophilia, and while their female offspring should not have hemophilia, they will each have a 50% chance of being carriers. e. All of their male offspring will have hemophilia, and while their female offspring should not have hemophilia, they will all be carriers.
Flowers and fruits are unique to
A. gymnosperms. B. angiosperms. C. conifers. D. bryophytes. E. cycads.
Double fertilization in an ovule of a flowering plant results in which of the following?
A. Two embryos B. Two seeds in a fruit C. One embryo and one endosperm D. Two fruits joined together E. One endosperm and one cotyledon
At the blood donation facility, you are completing an information form. The form asks about your health history and includes a question about whether you have ever had malaria or visited a country where malaria is endemic. Why is this information relevant?
A. Recipients differ in their susceptibility to malaria; if you have had malaria, the staff will earmark your blood to specific kinds of recipients. B. If you are infected with malaria, you are probably also infected with HIV, and that would disqualify your donation. C. Malarial parasites can persist in the liver, and, as a result, could be contaminating your blood and transferred to a recipient. D. This is just one of many pathogens that blood is screened for. The information given by the donor saves the staff time in testing the blood.