In research on aging (both cellular aging and organismal aging), it has been found that aged cells do not progress through the cell cycle as they had previously
Which of the following, if found in cells or organisms as they age, would provide evidence that this is related to cell signaling? A) Growth factor ligands do not bind as efficiently to receptors.
B) Hormone concentrations decrease.
C) cAMP levels change very frequently.
D) Enzymatic activity declines.
A
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Nitrogen is available to plants mostly in the form of _____
A) nitrogen in the atmosphere B) nitrite ions in the soil C) uric acid from animal excretions D) nucleic acids from decomposing plants and animals E) nitrate and ammonium ions in the soil
What is the formation of two species from one original species called?
a. natural selection b. evolution c. speciation d. divergence
The per capita growth rate (r) is ____ per mouse per month in a population of 1,000 mice where 500 mice are born
and 400 mice die monthly. a. 0.1 b. 0.2 c. 0.3 d. 0.4 e. 0.5
The cell membrane mix of lipids and proteins is referred to as a(n) ____
a. mixture b. compound c. suspension d. permeability e. mosaic