Conducting tubes of phloem consist of stacks of ____.?
A. dead sieve elements
B. living sieve elements
C. dead vessel elements
D. living vessel elements
E. dead companion cells
Answer: B. living sieve elements
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Aldosterone is a hormone secreted by the adrenal cortex, and insulin is a peptide secreted by the pancreas
When aldosterone contacts a target cell, it binds to an intracellular receptor and migrates to the nucleus; insulin binds to extracellular receptors on the plasma membrane. What is the most likely reason for this difference? A. Aldosterone is hydrophilic and therefore must enter the aqueous environment of the cytoplasm to have an effect. B. Aldosterone is lipid-soluble and therefore easily crosses the phospholipid bilayer of the plasma membrane. C. Aldosterone is too small to bind extracellular receptors on the plasma membrane. D. Insulin is too large to interact with DNA.
Approximately _____ percent of the Earth’s water is salt water
a. 3 b. 50 c. 65 d. 98
With ____ selection, the frequency of a favored allele will increase as a phenotypic variation becomes more adaptive
a. directional b. stabilizing c. disruptive d. frequent e. mutational
The dark middle layer of the eye that prevents the
scattering of light is the a. fovea. b. retina. c. sclera. d. choroid. e. cornea.