What is the role of myelin in neurons?
A. To change the direction that Na+ and K+ move through ion channels during the action potential
B. To increase the speed that action potentials travel down the neuron
C. To prevent the neuron from generating action potentials
D. To cause multiple sclerosis when present and intact, as it blocks action potential movement and must be envied by the immune system
Ans: B. To increase the speed that action potentials travel down the neuron
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At what location do the molecules and ions that are reabsorbed from the nephron re-enter the blood?
a. at the renal artery b. at the afferent arteriole c. at the efferent arteriole d. at the peritubular capillaries
Which statement is NOT true about ferns?
Select one: a. The gametophyte stage lacks vascular tissue. b. The sporophyte stage lacks vascular tissue. c. Antheridia and archegonia develop on the prothallus of the gametophyte stage. d. Fertilization requires moisture for the sperm to swim to the egg within the archegonia. e. The sporophyte stage is the dominant generation.
Geological evidence reveals that the barrier islands, where the populations of oldfield mice shown in the fig-ure above occur, formed only 6,000 years ago
Presumably, divergence in coat color has occurred since that time (Hoekstra et al. 2006). This is a very short time on the scale of evolutionary time. Explain how these dramatic variations in coat color between popula-tions could have occurred over such a relatively short time span. What will be an ideal response?
Vascular plant cells generally have the ability to differentiate into various types of tissue–a fact long known to horticulturists who propagate plants by cuttings
This means that plants do not display the strict separation of germline and somatic cells that animals do. Might this be expected to accelerate or decelerate evolution in plants relative to animals?