Explain the process of phototropism, including the role of auxin in this process
What will be an ideal response?
Phototropism orients certain parts of the plant in the direction that maximizes the amount of light intercepted by its photosynthetic cells. Phototropism in shoots occurs in response to blue light absorbed by nonphotosynthetic pigments called phototropins. In a shoot tip or coleoptile, light-energized phototropins repress transcription of a gene whose product causes auxin efflux carriers to be distributed evenly around the cell membrane. Thus, a cell exposed to a directional light source ends up with efflux carriers positioned mainly on its shady side. The polarization directs auxin flow toward the shaded side of the structure, causing cells on that side to elongate more than cells on the illuminated side. The difference causes the entire structure to bend toward the light as it lengthens.
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An oocyte released from a human ovary enters the oviduct as a result of _____
A) the beating action of the flagellum on the oocyte B) the force of the follicular ejection directing the oocyte into the oviduct C) the wavelike beating of cilia lining the oviduct D) movement of the oocyte through the pulsating uterus into the oviduct E) peristaltic contraction of ovarian muscles
Which of the following statements below is an incorrect link in human gamete production?
A. Gametogenesis produces gametes in human testes and ovaries. B. Human eggs are produced by oogenesis in the ovaries. C. Meiosis to form eggs is only completed if an egg cell is fertilized. D. Human sperm are formed through spermatogenesis in the testes. E. Gametes form after meiosis, in the process of parthenogenesis.
Which of the following would increase blood flow through a capillary bed?
A) contraction of precapillary sphincters in the capillary bed B) contraction of smooth muscle in the metarterioles bypassing the capillary bed C) constriction of the arteriole leading into the capillary bed D) decrease in blood pressure in the arteriole leading into the capillary bed E) increase in venous pressure
Which Ecdysozoan phylum contains members that have a segmented body encased in a rigid exoskeleton made of chitin plus other materials?
a. Annelida b. Nemertea c. Nematoda d. Arthropoda