In meiosis the spermatozoa that are produced are genetically unlike each other and unlike the cell that produces them. This is one reason for the great variation among humans. What causes this effect?
A) chromosome segregation and independent assortment only
B) crossing-over and chromosome segregation only
C) crossing-over and independent assortment only
D) crossing-over, chromosome segregation, and independent assortment
C
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What is found within the lacunae of bone?
A. Monocytes B. Osteoblasts C. Osteocytes D. Osteoclasts E. Chondrocytes
The mechanism for producing a concentrated urine involves all of the following except
A) the secretion of antidiuretic hormone (ADH) by the posterior pituitary gland. B) aquaporins being inserted into the membranes of the collecting duct cells. C) a high concentration of NaCl in the interstitial fluid that surrounds the collecting ducts. D) an increase in facultative water reabsorption. E) obligatory water reabsorption in the proximal convoluted tubule.
Contraction of the cremaster muscles
A) tenses the scrotum. B) pulls the testes closer to the body cavity. C) propels sperm through the urethra. D) moves sperm through the ductus deferens. E) tenses the scrotum and pulls the testes closer to the body cavity.
There are ________ pairs of spinal nerves.
A. 62 B. 31 C. 35 D. 12 E. 24