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Free CLEP Science and Mathematics Exam Braindumps (page: 15)

Page 14 of 128
PDF with 494 Questions

In contrast to spermatogenesis, oogenesis

  1. produces one functional haploid cell for every diploid cell that begins the process
  2. is started by the hormones FSH and LH
  3. takes place in the fallopian tubes
  4. produces gametes
  5. features equal divisions of cytoplasm and organelles into daughter cells

Answer(s): A

Explanation:

Oogenesis, the formation of egg cells (ova) in the female, takes place in the ovaries each month. Because there is an evolutionary advantage to having a large ovum, complete with a supply of organelles, at the end of the process, there is unequal division of the cells leading up to the egg. The result: three polar bodies, which are nonfunctional and will be destroyed, and one large, functional egg cell. Spermatogenesis, in contrast, produces four sperm cells for every diploid spermatocyte that starts the process.



The white blood cells responsible for attacking specific pathogens with antibodies are a type of

  1. erythrocyte
  2. lymphocyte
  3. neutrophil
  4. macrophage
  5. platelet

Answer(s): B

Explanation:

The lymphocytes are B and T cells, the specific arms of the immune system, producing antibodies and enzymes that destroy pathogens. Erythrocytes are red blood cells, while neutrophils and macrophages engulf and destroy pathogens directly.
Platelets are involved in clotting.



Guard cells are kidney-shaped cells surrounding the stomata on the underside of leaves. These cells change their shape according to the amount of water that exists within them. The more water within, the more swollen the guard cells are and the stomata open. When water is sparse the guard cells shrivel and close the stomata. Recent evidence suggests that there are blue-light receptors on the plasma membrane surface of guard cells that are coupled to potassium (K+) ion channels. K+ ions are normally found in high concentration outside guard cell membranes when the channels are closed.

What mechanism may account for the fact that guard cells are usually open during the day and closed at night?

  1. Photosynthesis uses K+ ions; therefore, lower concentrations of potassium within the leaf drive the movement of K+ into the leaf through the guard cells.
  2. The presence of sunlight drives K+ into guard cells, while driving water out of the guard cells and opening the stomata.
  3. There is more water in the air during daylight hours than during nighttime hours.
  4. K+ ions enter the cell through active transport only when enough water is present.
  5. The presence of sunlight opens the K+ ion channels, driving potassium inside, and causing water to follow by osmosis, swelling the guard cells.

Answer(s): E

Explanation:

The information about guard cells states that they must be swollen with water in order for them to open the stomata. It is advantageous to have the stomata open during the day, since that is when the sun is shining for photosynthesis to take place. Light falling on the blue-light receptors causes an influx of potassium ions, which draw water into the guard cells via osmosis. This causes the stomata to open.



Pollen grains are produced by meiosis on which of the following parts of a flowering plant?

  1. Sepal
  2. Style
  3. Stigma
  4. Anther
  5. Filament

Answer(s): D

Explanation:

The anther is the male part of the flower, on which pollen grains are produced.






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